doc/src/sgml/catalogs.sgml

   1 <!-- $PostgreSQL$ -->
   2 <!--
   3  Documentation of the system catalogs, directed toward PostgreSQL developers
   4  -->
   5
   6 <chapter id="catalogs">
   7  <title>System Catalogs</title>
   8
   9   <para>
  10    The system catalogs are the place where a relational database
  11    management system stores schema metadata, such as information about
  12    tables and columns, and internal bookkeeping information.
  13    <productname>PostgreSQL</productname>'s system catalogs are regular
  14    tables.  You can drop and recreate the tables, add columns, insert
  15    and update values, and severely mess up your system that way.
  16    Normally, one should not change the system catalogs by hand, there
  17    are always SQL commands to do that.  (For example, <command>CREATE
  18    DATABASE</command> inserts a row into the
  19    <structname>pg_database</structname> catalog &mdash; and actually
  20    creates the database on disk.)  There are some exceptions for
  21    particularly esoteric operations, such as adding index access methods.
  22   </para>
  23
  24  <sect1 id="catalogs-overview">
  25   <title>Overview</title>
  26
  27   <para>
  28    <xref linkend="catalog-table"> lists the system catalogs.
  29    More detailed documentation of each catalog follows below.
  30   </para>
  31
  32   <para>
  33    Most system catalogs are copied from the template database during
  34    database creation and are thereafter database-specific. A few
  35    catalogs are physically shared across all databases in a cluster;
  36    these are noted in the descriptions of the individual catalogs.
  37   </para>
  38
  39   <table id="catalog-table">
  40    <title>System Catalogs</title>
  41
  42    <tgroup cols="2">
  43     <thead>
  44      <row>
  45       <entry>Catalog Name</entry>
  46       <entry>Purpose</entry>
  47      </row>
  48     </thead>
  49
  50     <tbody>
  51      <row>
  52       <entry><link linkend="catalog-pg-aggregate"><structname>pg_aggregate</structname></link></entry>
  53       <entry>aggregate functions</entry>
  54      </row>
  55
  56      <row>
  57       <entry><link linkend="catalog-pg-am"><structname>pg_am</structname></link></entry>
  58       <entry>index access methods</entry>
  59      </row>
  60
  61      <row>
  62       <entry><link linkend="catalog-pg-amop"><structname>pg_amop</structname></link></entry>
  63       <entry>access method operators</entry>
  64      </row>
  65
  66      <row>
  67       <entry><link linkend="catalog-pg-amproc"><structname>pg_amproc</structname></link></entry>
  68       <entry>access method support procedures</entry>
  69      </row>
  70
  71      <row>
  72       <entry><link linkend="catalog-pg-attrdef"><structname>pg_attrdef</structname></link></entry>
  73       <entry>column default values</entry>
  74      </row>
  75
  76      <row>
  77       <entry><link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link></entry>
  78       <entry>table columns (<quote>attributes</quote>)</entry>
  79      </row>
  80
  81      <row>
  82       <entry><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link></entry>
  83       <entry>authorization identifiers (roles)</entry>
  84      </row>
  85
  86      <row>
  87       <entry><link linkend="catalog-pg-auth-members"><structname>pg_auth_members</structname></link></entry>
  88       <entry>authorization identifier membership relationships</entry>
  89      </row>
  90
  91      <row>
  92       <entry><link linkend="catalog-pg-cast"><structname>pg_cast</structname></link></entry>
  93       <entry>casts (data type conversions)</entry>
  94      </row>
  95
  96      <row>
  97       <entry><link linkend="catalog-pg-class"><structname>pg_class</structname></link></entry>
  98       <entry>tables, indexes, sequences, views (<quote>relations</quote>)</entry>
  99      </row>
 100
 101      <row>
 102       <entry><link linkend="catalog-pg-constraint"><structname>pg_constraint</structname></link></entry>
 103       <entry>check constraints, unique constraints, primary key constraints, foreign key constraints</entry>
 104      </row>
 105
 106      <row>
 107       <entry><link linkend="catalog-pg-conversion"><structname>pg_conversion</structname></link></entry>
 108       <entry>encoding conversion information</entry>
 109      </row>
 110
 111      <row>
 112       <entry><link linkend="catalog-pg-database"><structname>pg_database</structname></link></entry>
 113       <entry>databases within this database cluster</entry>
 114      </row>
 115
 116      <row>
 117       <entry><link linkend="catalog-pg-default-acl"><structname>pg_default_acl</structname></link></entry>
 118       <entry>default privileges for object types</entry>
 119      </row>
 120
 121      <row>
 122       <entry><link linkend="catalog-pg-depend"><structname>pg_depend</structname></link></entry>
 123       <entry>dependencies between database objects</entry>
 124      </row>
 125
 126      <row>
 127       <entry><link linkend="catalog-pg-description"><structname>pg_description</structname></link></entry>
 128       <entry>descriptions or comments on database objects</entry>
 129      </row>
 130
 131      <row>
 132       <entry><link linkend="catalog-pg-enum"><structname>pg_enum</structname></link></entry>
 133       <entry>enum label and value definitions</entry>
 134      </row>
 135
 136      <row>
 137       <entry><link linkend="catalog-pg-foreign-data-wrapper"><structname>pg_foreign_data_wrapper</structname></link></entry>
 138       <entry>foreign-data wrapper definitions</entry>
 139      </row>
 140
 141      <row>
 142       <entry><link linkend="catalog-pg-foreign-server"><structname>pg_foreign_server</structname></link></entry>
 143       <entry>foreign server definitions</entry>
 144      </row>
 145
 146      <row>
 147       <entry><link linkend="catalog-pg-foreign-table"><structname>pg_foreign_table</structname></link></entry>
 148       <entry>additional foreign table information</entry>
 149      </row>
 150
 151      <row>
 152       <entry><link linkend="catalog-pg-index"><structname>pg_index</structname></link></entry>
 153       <entry>additional index information</entry>
 154      </row>
 155
 156      <row>
 157       <entry><link linkend="catalog-pg-inherits"><structname>pg_inherits</structname></link></entry>
 158       <entry>table inheritance hierarchy</entry>
 159      </row>
 160
 161      <row>
 162       <entry><link linkend="catalog-pg-language"><structname>pg_language</structname></link></entry>
 163       <entry>languages for writing functions</entry>
 164      </row>
 165
 166      <row>
 167       <entry><link linkend="catalog-pg-largeobject"><structname>pg_largeobject</structname></link></entry>
 168       <entry>data pages for large objects</entry>
 169      </row>
 170
 171      <row>
 172       <entry><link linkend="catalog-pg-largeobject-metadata"><structname>pg_largeobject_metadata</structname></link></entry>
 173       <entry>metadata for large objects</entry>
 174      </row>
 175
 176      <row>
 177       <entry><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link></entry>
 178       <entry>schemas</entry>
 179      </row>
 180
 181      <row>
 182       <entry><link linkend="catalog-pg-opclass"><structname>pg_opclass</structname></link></entry>
 183       <entry>access method operator classes</entry>
 184      </row>
 185
 186      <row>
 187       <entry><link linkend="catalog-pg-operator"><structname>pg_operator</structname></link></entry>
 188       <entry>operators</entry>
 189      </row>
 190
 191      <row>
 192       <entry><link linkend="catalog-pg-opfamily"><structname>pg_opfamily</structname></link></entry>
 193       <entry>access method operator families</entry>
 194      </row>
 195
 196      <row>
 197       <entry><link linkend="catalog-pg-pltemplate"><structname>pg_pltemplate</structname></link></entry>
 198       <entry>template data for procedural languages</entry>
 199      </row>
 200
 201      <row>
 202       <entry><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link></entry>
 203       <entry>functions and procedures</entry>
 204      </row>
 205
 206      <row>
 207       <entry><link linkend="catalog-pg-rewrite"><structname>pg_rewrite</structname></link></entry>
 208       <entry>query rewrite rules</entry>
 209      </row>
 210
 211      <row>
 212       <entry><link linkend="catalog-pg-db-role-setting"><structname>pg_db_role_setting</structname></link></entry>
 213       <entry>per-role and per-database settings</entry>
 214      </row>
 215
 216      <row>
 217       <entry><link linkend="catalog-pg-shdepend"><structname>pg_shdepend</structname></link></entry>
 218       <entry>dependencies on shared objects</entry>
 219      </row>
 220
 221      <row>
 222       <entry><link linkend="catalog-pg-shdescription"><structname>pg_shdescription</structname></link></entry>
 223       <entry>comments on shared objects</entry>
 224      </row>
 225
 226      <row>
 227       <entry><link linkend="catalog-pg-statistic"><structname>pg_statistic</structname></link></entry>
 228       <entry>planner statistics</entry>
 229      </row>
 230
 231      <row>
 232       <entry><link linkend="catalog-pg-tablespace"><structname>pg_tablespace</structname></link></entry>
 233       <entry>tablespaces within this database cluster</entry>
 234      </row>
 235
 236      <row>
 237       <entry><link linkend="catalog-pg-trigger"><structname>pg_trigger</structname></link></entry>
 238       <entry>triggers</entry>
 239      </row>
 240
 241      <row>
 242       <entry><link linkend="catalog-pg-ts-config"><structname>pg_ts_config</structname></link></entry>
 243       <entry>text search configurations</entry>
 244      </row>
 245
 246      <row>
 247       <entry><link linkend="catalog-pg-ts-config-map"><structname>pg_ts_config_map</structname></link></entry>
 248       <entry>text search configurations' token mappings</entry>
 249      </row>
 250
 251      <row>
 252       <entry><link linkend="catalog-pg-ts-dict"><structname>pg_ts_dict</structname></link></entry>
 253       <entry>text search dictionaries</entry>
 254      </row>
 255
 256      <row>
 257       <entry><link linkend="catalog-pg-ts-parser"><structname>pg_ts_parser</structname></link></entry>
 258       <entry>text search parsers</entry>
 259      </row>
 260
 261      <row>
 262       <entry><link linkend="catalog-pg-ts-template"><structname>pg_ts_template</structname></link></entry>
 263       <entry>text search templates</entry>
 264      </row>
 265
 266      <row>
 267       <entry><link linkend="catalog-pg-type"><structname>pg_type</structname></link></entry>
 268       <entry>data types</entry>
 269      </row>
 270
 271      <row>
 272       <entry><link linkend="catalog-pg-user-mapping"><structname>pg_user_mapping</structname></link></entry>
 273       <entry>mappings of users to foreign servers</entry>
 274      </row>
 275     </tbody>
 276    </tgroup>
 277   </table>
 278  </sect1>
 279
 280
 281  <sect1 id="catalog-pg-aggregate">
 282   <title><structname>pg_aggregate</structname></title>
 283
 284   <indexterm zone="catalog-pg-aggregate">
 285    <primary>pg_aggregate</primary>
 286   </indexterm>
 287
 288   <para>
 289    The catalog <structname>pg_aggregate</structname> stores information about
 290    aggregate functions.  An aggregate function is a function that
 291    operates on a set of values (typically one column from each row
 292    that matches a query condition) and returns a single value computed
 293    from all these values.  Typical aggregate functions are
 294    <function>sum</function>, <function>count</function>, and
 295    <function>max</function>.  Each entry in
 296    <structname>pg_aggregate</structname> is an extension of an entry
 297    in <structname>pg_proc</structname>.  The <structname>pg_proc</structname>
 298    entry carries the aggregate's name, input and output data types, and
 299    other information that is similar to ordinary functions.
 300   </para>
 301
 302   <table>
 303    <title><structname>pg_aggregate</> Columns</title>
 304
 305    <tgroup cols="4">
 306     <thead>
 307      <row>
 308       <entry>Name</entry>
 309       <entry>Type</entry>
 310       <entry>References</entry>
 311       <entry>Description</entry>
 312      </row>
 313     </thead>
 314     <tbody>
 315      <row>
 316       <entry><structfield>aggfnoid</structfield></entry>
 317       <entry><type>regproc</type></entry>
 318       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
 319       <entry><structname>pg_proc</structname> OID of the aggregate function</entry>
 320      </row>
 321      <row>
 322       <entry><structfield>aggtransfn</structfield></entry>
 323       <entry><type>regproc</type></entry>
 324       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
 325       <entry>Transition function</entry>
 326      </row>
 327      <row>
 328       <entry><structfield>aggfinalfn</structfield></entry>
 329       <entry><type>regproc</type></entry>
 330       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
 331       <entry>Final function (zero if none)</entry>
 332      </row>
 333      <row>
 334       <entry><structfield>aggsortop</structfield></entry>
 335       <entry><type>oid</type></entry>
 336       <entry><literal><link linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.oid</literal></entry>
 337       <entry>Associated sort operator (zero if none)</entry>
 338      </row>
 339      <row>
 340       <entry><structfield>aggtranstype</structfield></entry>
 341       <entry><type>oid</type></entry>
 342       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
 343       <entry>Data type of the aggregate function's internal transition (state) data</entry>
 344      </row>
 345      <row>
 346       <entry><structfield>agginitval</structfield></entry>
 347       <entry><type>text</type></entry>
 348       <entry></entry>
 349       <entry>
 350        The initial value of the transition state.  This is a text
 351        field containing the initial value in its external string
 352        representation.  If this field is null, the transition state
 353        value starts out null.
 354       </entry>
 355      </row>
 356     </tbody>
 357    </tgroup>
 358   </table>
 359
 360   <para>
 361    New aggregate functions are registered with the <xref
 362    linkend="sql-createaggregate">
 363    command.  See <xref linkend="xaggr"> for more information about
 364    writing aggregate functions and the meaning of the transition
 365    functions, etc.
 366   </para>
 367
 368  </sect1>
 369
 370
 371  <sect1 id="catalog-pg-am">
 372   <title><structname>pg_am</structname></title>
 373
 374   <indexterm zone="catalog-pg-am">
 375    <primary>pg_am</primary>
 376   </indexterm>
 377
 378   <para>
 379    The catalog <structname>pg_am</structname> stores information about index
 380    access methods.  There is one row for each index access method supported by
 381    the system.  The contents of this catalog are discussed in detail in
 382    <xref linkend="indexam">.
 383   </para>
 384
 385   <table>
 386    <title><structname>pg_am</> Columns</title>
 387
 388    <tgroup cols="4">
 389     <thead>
 390      <row>
 391       <entry>Name</entry>
 392       <entry>Type</entry>
 393       <entry>References</entry>
 394       <entry>Description</entry>
 395      </row>
 396     </thead>
 397     <tbody>
 398
 399      <row>
 400       <entry><structfield>amname</structfield></entry>
 401       <entry><type>name</type></entry>
 402       <entry></entry>
 403       <entry>Name of the access method</entry>
 404      </row>
 405
 406      <row>
 407       <entry><structfield>amstrategies</structfield></entry>
 408       <entry><type>int2</type></entry>
 409       <entry></entry>
 410       <entry>Number of operator strategies for this access method,
 411        or zero if access method does not have a fixed set of operator
 412        strategies</entry>
 413      </row>
 414
 415      <row>
 416       <entry><structfield>amsupport</structfield></entry>
 417       <entry><type>int2</type></entry>
 418       <entry></entry>
 419       <entry>Number of support routines for this access method</entry>
 420      </row>
 421
 422      <row>
 423       <entry><structfield>amcanorder</structfield></entry>
 424       <entry><type>bool</type></entry>
 425       <entry></entry>
 426       <entry>Does the access method support ordered scans?</entry>
 427      </row>
 428
 429      <row>
 430       <entry><structfield>amcanbackward</structfield></entry>
 431       <entry><type>bool</type></entry>
 432       <entry></entry>
 433       <entry>Does the access method support backward scanning?</entry>
 434      </row>
 435
 436      <row>
 437       <entry><structfield>amcanunique</structfield></entry>
 438       <entry><type>bool</type></entry>
 439       <entry></entry>
 440       <entry>Does the access method support unique indexes?</entry>
 441      </row>
 442
 443      <row>
 444       <entry><structfield>amcanmulticol</structfield></entry>
 445       <entry><type>bool</type></entry>
 446       <entry></entry>
 447       <entry>Does the access method support multicolumn indexes?</entry>
 448      </row>
 449
 450      <row>
 451       <entry><structfield>amoptionalkey</structfield></entry>
 452       <entry><type>bool</type></entry>
 453       <entry></entry>
 454       <entry>Does the access method support a scan without any constraint
 455        for the first index column?</entry>
 456      </row>
 457
 458      <row>
 459       <entry><structfield>amindexnulls</structfield></entry>
 460       <entry><type>bool</type></entry>
 461       <entry></entry>
 462       <entry>Does the access method support null index entries?</entry>
 463      </row>
 464
 465      <row>
 466       <entry><structfield>amsearchnulls</structfield></entry>
 467       <entry><type>bool</type></entry>
 468       <entry></entry>
 469       <entry>Does the access method support <literal>IS NULL</>/<literal>NOT NULL</> searches?</entry>
 470      </row>
 471
 472      <row>
 473       <entry><structfield>amstorage</structfield></entry>
 474       <entry><type>bool</type></entry>
 475       <entry></entry>
 476       <entry>Can index storage data type differ from column data type?</entry>
 477      </row>
 478
 479      <row>
 480       <entry><structfield>amclusterable</structfield></entry>
 481       <entry><type>bool</type></entry>
 482       <entry></entry>
 483       <entry>Can an index of this type be clustered on?</entry>
 484      </row>
 485
 486      <row>
 487       <entry><structfield>amkeytype</structfield></entry>
 488       <entry><type>oid</type></entry>
 489       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
 490       <entry>Type of data stored in index, or zero if not a fixed type</entry>
 491      </row>
 492
 493      <row>
 494       <entry><structfield>aminsert</structfield></entry>
 495       <entry><type>regproc</type></entry>
 496       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
 497       <entry><quote>Insert this tuple</quote> function</entry>
 498      </row>
 499
 500      <row>
 501       <entry><structfield>ambeginscan</structfield></entry>
 502       <entry><type>regproc</type></entry>
 503       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
 504       <entry><quote>Start new scan</quote> function</entry>
 505      </row>
 506
 507      <row>
 508       <entry><structfield>amgettuple</structfield></entry>
 509       <entry><type>regproc</type></entry>
 510       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
 511       <entry><quote>Next valid tuple</quote> function, or zero if none</entry>
 512      </row>
 513
 514      <row>
 515       <entry><structfield>amgetbitmap</structfield></entry>
 516       <entry><type>regproc</type></entry>
 517       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
 518       <entry><quote>Fetch all valid tuples</quote> function, or zero if none</entry>
 519      </row>
 520
 521      <row>
 522       <entry><structfield>amrescan</structfield></entry>
 523       <entry><type>regproc</type></entry>
 524       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
 525       <entry><quote>Restart this scan</quote> function</entry>
 526      </row>
 527
 528      <row>
 529       <entry><structfield>amendscan</structfield></entry>
 530       <entry><type>regproc</type></entry>
 531       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
 532       <entry><quote>End this scan</quote> function</entry>
 533      </row>
 534
 535      <row>
 536       <entry><structfield>ammarkpos</structfield></entry>
 537       <entry><type>regproc</type></entry>
 538       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
 539       <entry><quote>Mark current scan position</quote> function</entry>
 540      </row>
 541
 542      <row>
 543       <entry><structfield>amrestrpos</structfield></entry>
 544       <entry><type>regproc</type></entry>
 545       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
 546       <entry><quote>Restore marked scan position</quote> function</entry>
 547      </row>
 548
 549      <row>
 550       <entry><structfield>ambuild</structfield></entry>
 551       <entry><type>regproc</type></entry>
 552       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
 553       <entry><quote>Build new index</quote> function</entry>
 554      </row>
 555
 556      <row>
 557       <entry><structfield>ambulkdelete</structfield></entry>
 558       <entry><type>regproc</type></entry>
 559       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
 560       <entry>Bulk-delete function</entry>
 561      </row>
 562
 563      <row>
 564       <entry><structfield>amvacuumcleanup</structfield></entry>
 565       <entry><type>regproc</type></entry>
 566       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
 567       <entry>Post-<command>VACUUM</command> cleanup function</entry>
 568      </row>
 569
 570      <row>
 571       <entry><structfield>amcostestimate</structfield></entry>
 572       <entry><type>regproc</type></entry>
 573       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
 574       <entry>Function to estimate cost of an index scan</entry>
 575      </row>
 576
 577      <row>
 578       <entry><structfield>amoptions</structfield></entry>
 579       <entry><type>regproc</type></entry>
 580       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
 581       <entry>Function to parse and validate <structfield>reloptions</> for an index</entry>
 582      </row>
 583
 584     </tbody>
 585    </tgroup>
 586   </table>
 587
 588  </sect1>
 589
 590
 591  <sect1 id="catalog-pg-amop">
 592   <title><structname>pg_amop</structname></title>
 593
 594   <indexterm zone="catalog-pg-amop">
 595    <primary>pg_amop</primary>
 596   </indexterm>
 597
 598   <para>
 599    The catalog <structname>pg_amop</structname> stores information about
 600    operators associated with access method operator families.  There is one
 601    row for each operator that is a member of an operator family.  An operator
 602    can appear in more than one family, but cannot appear in more than one
 603    position within a family.
 604   </para>
 605
 606   <table>
 607    <title><structname>pg_amop</> Columns</title>
 608
 609    <tgroup cols="4">
 610     <thead>
 611      <row>
 612       <entry>Name</entry>
 613       <entry>Type</entry>
 614       <entry>References</entry>
 615       <entry>Description</entry>
 616      </row>
 617     </thead>
 618     <tbody>
 619
 620      <row>
 621       <entry><structfield>amopfamily</structfield></entry>
 622       <entry><type>oid</type></entry>
 623       <entry><literal><link linkend="catalog-pg-opfamily"><structname>pg_opfamily</structname></link>.oid</literal></entry>
 624       <entry>The operator family this entry is for</entry>
 625      </row>
 626
 627      <row>
 628       <entry><structfield>amoplefttype</structfield></entry>
 629       <entry><type>oid</type></entry>
 630       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
 631       <entry>Left-hand input data type of operator</entry>
 632      </row>
 633
 634      <row>
 635       <entry><structfield>amoprighttype</structfield></entry>
 636       <entry><type>oid</type></entry>
 637       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
 638       <entry>Right-hand input data type of operator</entry>
 639      </row>
 640
 641      <row>
 642       <entry><structfield>amopstrategy</structfield></entry>
 643       <entry><type>int2</type></entry>
 644       <entry></entry>
 645       <entry>Operator strategy number</entry>
 646      </row>
 647
 648      <row>
 649       <entry><structfield>amopopr</structfield></entry>
 650       <entry><type>oid</type></entry>
 651       <entry><literal><link linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.oid</literal></entry>
 652       <entry>OID of the operator</entry>
 653      </row>
 654
 655      <row>
 656       <entry><structfield>amopmethod</structfield></entry>
 657       <entry><type>oid</type></entry>
 658       <entry><literal><link linkend="catalog-pg-am"><structname>pg_am</structname></link>.oid</literal></entry>
 659       <entry>Index access method operator family is for</entry>
 660      </row>
 661
 662     </tbody>
 663    </tgroup>
 664   </table>
 665
 666   <para>
 667    An entry's <structfield>amopmethod</> must match the
 668    <structname>opfmethod</> of its containing operator family (including
 669    <structfield>amopmethod</> here is an intentional denormalization of the
 670    catalog structure for performance reasons).  Also,
 671    <structfield>amoplefttype</> and <structfield>amoprighttype</> must match
 672    the <structfield>oprleft</> and <structfield>oprright</> fields of the
 673    referenced <structname>pg_operator</> entry.
 674   </para>
 675
 676  </sect1>
 677
 678
 679  <sect1 id="catalog-pg-amproc">
 680   <title><structname>pg_amproc</structname></title>
 681
 682   <indexterm zone="catalog-pg-amproc">
 683    <primary>pg_amproc</primary>
 684   </indexterm>
 685
 686   <para>
 687    The catalog <structname>pg_amproc</structname> stores information about
 688    support procedures associated with access method operator families.  There
 689    is one row for each support procedure belonging to an operator family.
 690   </para>
 691
 692   <table>
 693    <title><structname>pg_amproc</structname> Columns</title>
 694
 695    <tgroup cols="4">
 696     <thead>
 697      <row>
 698       <entry>Name</entry>
 699       <entry>Type</entry>
 700       <entry>References</entry>
 701       <entry>Description</entry>
 702      </row>
 703     </thead>
 704     <tbody>
 705
 706      <row>
 707       <entry><structfield>amprocfamily</structfield></entry>
 708       <entry><type>oid</type></entry>
 709       <entry><literal><link linkend="catalog-pg-opfamily"><structname>pg_opfamily</structname></link>.oid</literal></entry>
 710       <entry>The operator family this entry is for</entry>
 711      </row>
 712
 713      <row>
 714       <entry><structfield>amproclefttype</structfield></entry>
 715       <entry><type>oid</type></entry>
 716       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
 717       <entry>Left-hand input data type of associated operator</entry>
 718      </row>
 719
 720      <row>
 721       <entry><structfield>amprocrighttype</structfield></entry>
 722       <entry><type>oid</type></entry>
 723       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
 724       <entry>Right-hand input data type of associated operator</entry>
 725      </row>
 726
 727      <row>
 728       <entry><structfield>amprocnum</structfield></entry>
 729       <entry><type>int2</type></entry>
 730       <entry></entry>
 731       <entry>Support procedure number</entry>
 732      </row>
 733
 734      <row>
 735       <entry><structfield>amproc</structfield></entry>
 736       <entry><type>regproc</type></entry>
 737       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
 738       <entry>OID of the procedure</entry>
 739      </row>
 740
 741     </tbody>
 742    </tgroup>
 743   </table>
 744
 745   <para>
 746    The usual interpretation of the
 747    <structfield>amproclefttype</> and <structfield>amprocrighttype</> fields
 748    is that they identify the left and right input types of the operator(s)
 749    that a particular support procedure supports.  For some access methods
 750    these match the input data type(s) of the support procedure itself, for
 751    others not.  There is a notion of <quote>default</> support procedures for
 752    an index, which are those with <structfield>amproclefttype</> and
 753    <structfield>amprocrighttype</> both equal to the index opclass's
 754    <structfield>opcintype</>.
 755   </para>
 756
 757  </sect1>
 758
 759
 760  <sect1 id="catalog-pg-attrdef">
 761   <title><structname>pg_attrdef</structname></title>
 762
 763   <indexterm zone="catalog-pg-attrdef">
 764    <primary>pg_attrdef</primary>
 765   </indexterm>
 766
 767   <para>
 768    The catalog <structname>pg_attrdef</structname> stores column default values.  The main information
 769    about columns is stored in <structname>pg_attribute</structname>
 770    (see below).  Only columns that explicitly specify a default value
 771    (when the table is created or the column is added) will have an
 772    entry here.
 773   </para>
 774
 775   <table>
 776    <title><structname>pg_attrdef</> Columns</title>
 777
 778    <tgroup cols="4">
 779     <thead>
 780      <row>
 781       <entry>Name</entry>
 782       <entry>Type</entry>
 783       <entry>References</entry>
 784       <entry>Description</entry>
 785      </row>
 786     </thead>
 787
 788     <tbody>
 789      <row>
 790       <entry><structfield>adrelid</structfield></entry>
 791       <entry><type>oid</type></entry>
 792       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
 793       <entry>The table this column belongs to</entry>
 794      </row>
 795
 796      <row>
 797       <entry><structfield>adnum</structfield></entry>
 798       <entry><type>int2</type></entry>
 799       <entry><literal><link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.attnum</literal></entry>
 800       <entry>The number of the column</entry>
 801      </row>
 802
 803      <row>
 804       <entry><structfield>adbin</structfield></entry>
 805       <entry><type>pg_node_tree</type></entry>
 806       <entry></entry>
 807       <entry>The internal representation of the column default value</entry>
 808      </row>
 809
 810      <row>
 811       <entry><structfield>adsrc</structfield></entry>
 812       <entry><type>text</type></entry>
 813       <entry></entry>
 814       <entry>A human-readable representation of the default value</entry>
 815      </row>
 816     </tbody>
 817    </tgroup>
 818   </table>
 819
 820    <para>
 821     The <structfield>adsrc</structfield> field is historical, and is best
 822     not used, because it does not track outside changes that might affect
 823     the representation of the default value.  Reverse-compiling the
 824     <structfield>adbin</structfield> field (with <function>pg_get_expr</> for
 825     example) is a better way to display the default value.
 826    </para>
 827
 828  </sect1>
 829
 830
 831  <sect1 id="catalog-pg-attribute">
 832   <title><structname>pg_attribute</structname></title>
 833
 834   <indexterm zone="catalog-pg-attribute">
 835    <primary>pg_attribute</primary>
 836   </indexterm>
 837
 838   <para>
 839    The catalog <structname>pg_attribute</structname> stores information about
 840    table columns.  There will be exactly one
 841    <structname>pg_attribute</structname> row for every column in every
 842    table in the database.  (There will also be attribute entries for
 843    indexes, and indeed all objects that have <structname>pg_class</structname>
 844    entries.)
 845   </para>
 846
 847   <para>
 848    The term attribute is equivalent to column and is used for
 849    historical reasons.
 850   </para>
 851
 852   <table>
 853    <title><structname>pg_attribute</> Columns</title>
 854
 855    <tgroup cols="4">
 856     <thead>
 857      <row>
 858       <entry>Name</entry>
 859       <entry>Type</entry>
 860       <entry>References</entry>
 861       <entry>Description</entry>
 862      </row>
 863     </thead>
 864
 865     <tbody>
 866      <row>
 867       <entry><structfield>attrelid</structfield></entry>
 868       <entry><type>oid</type></entry>
 869       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
 870       <entry>The table this column belongs to</entry>
 871      </row>
 872
 873      <row>
 874       <entry><structfield>attname</structfield></entry>
 875       <entry><type>name</type></entry>
 876       <entry></entry>
 877       <entry>The column name</entry>
 878      </row>
 879
 880      <row>
 881       <entry><structfield>atttypid</structfield></entry>
 882       <entry><type>oid</type></entry>
 883       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
 884       <entry>The data type of this column</entry>
 885      </row>
 886
 887      <row>
 888       <entry><structfield>attstattarget</structfield></entry>
 889       <entry><type>int4</type></entry>
 890       <entry></entry>
 891       <entry>
 892        <structfield>attstattarget</structfield> controls the level of detail
 893        of statistics accumulated for this column by
 894        <xref linkend="sql-analyze">.
 895        A zero value indicates that no statistics should be collected.
 896        A negative value says to use the system default statistics target.
 897        The exact meaning of positive values is data type-dependent.
 898        For scalar data types, <structfield>attstattarget</structfield>
 899        is both the target number of <quote>most common values</quote>
 900        to collect, and the target number of histogram bins to create.
 901       </entry>
 902      </row>
 903
 904      <row>
 905       <entry><structfield>attlen</structfield></entry>
 906       <entry><type>int2</type></entry>
 907       <entry></entry>
 908       <entry>
 909        A copy of <literal>pg_type.typlen</literal> of this column's
 910        type
 911       </entry>
 912      </row>
 913
 914      <row>
 915       <entry><structfield>attnum</structfield></entry>
 916       <entry><type>int2</type></entry>
 917       <entry></entry>
 918       <entry>
 919        The number of the column.  Ordinary columns are numbered from 1
 920        up.  System columns, such as <structfield>oid</structfield>,
 921        have (arbitrary) negative numbers.
 922       </entry>
 923      </row>
 924
 925      <row>
 926       <entry><structfield>attndims</structfield></entry>
 927       <entry><type>int4</type></entry>
 928       <entry></entry>
 929       <entry>
 930        Number of dimensions, if the column is an array type; otherwise 0.
 931        (Presently, the number of dimensions of an array is not enforced,
 932        so any nonzero value effectively means <quote>it's an array</>.)
 933       </entry>
 934      </row>
 935
 936      <row>
 937       <entry><structfield>attcacheoff</structfield></entry>
 938       <entry><type>int4</type></entry>
 939       <entry></entry>
 940       <entry>
 941        Always -1 in storage, but when loaded into a row descriptor
 942        in memory this might be updated to cache the offset of the attribute
 943        within the row
 944       </entry>
 945      </row>
 946
 947      <row>
 948       <entry><structfield>atttypmod</structfield></entry>
 949       <entry><type>int4</type></entry>
 950       <entry></entry>
 951       <entry>
 952        <structfield>atttypmod</structfield> records type-specific data
 953        supplied at table creation time (for example, the maximum
 954        length of a <type>varchar</type> column).  It is passed to
 955        type-specific input functions and length coercion functions.
 956        The value will generally be -1 for types that do not need <structfield>atttypmod</>.
 957       </entry>
 958      </row>
 959
 960      <row>
 961       <entry><structfield>attbyval</structfield></entry>
 962       <entry><type>bool</type></entry>
 963       <entry></entry>
 964       <entry>
 965        A copy of <literal>pg_type.typbyval</> of this column's type
 966       </entry>
 967      </row>
 968
 969      <row>
 970       <entry><structfield>attstorage</structfield></entry>
 971       <entry><type>char</type></entry>
 972       <entry></entry>
 973       <entry>
 974        Normally a copy of <literal>pg_type.typstorage</> of this
 975        column's type.  For TOAST-able data types, this can be altered
 976        after column creation to control storage policy.
 977       </entry>
 978      </row>
 979
 980      <row>
 981       <entry><structfield>attalign</structfield></entry>
 982       <entry><type>char</type></entry>
 983       <entry></entry>
 984       <entry>
 985        A copy of <literal>pg_type.typalign</> of this column's type
 986       </entry>
 987      </row>
 988
 989      <row>
 990       <entry><structfield>attnotnull</structfield></entry>
 991       <entry><type>bool</type></entry>
 992       <entry></entry>
 993       <entry>
 994        This represents a not-null constraint.  It is possible to
 995        change this column to enable or disable the constraint.
 996       </entry>
 997      </row>
 998
 999      <row>
1000       <entry><structfield>atthasdef</structfield></entry>
1001       <entry><type>bool</type></entry>
1002       <entry></entry>
1003       <entry>
1004        This column has a default value, in which case there will be a
1005        corresponding entry in the <structname>pg_attrdef</structname>
1006        catalog that actually defines the value.
1007       </entry>
1008      </row>
1009
1010      <row>
1011       <entry><structfield>attisdropped</structfield></entry>
1012       <entry><type>bool</type></entry>
1013       <entry></entry>
1014       <entry>
1015        This column has been dropped and is no longer valid.  A dropped
1016        column is still physically present in the table, but is
1017        ignored by the parser and so cannot be accessed via SQL.
1018       </entry>
1019      </row>
1020
1021      <row>
1022       <entry><structfield>attislocal</structfield></entry>
1023       <entry><type>bool</type></entry>
1024       <entry></entry>
1025       <entry>
1026        This column is defined locally in the relation.  Note that a column can
1027        be locally defined and inherited simultaneously.
1028       </entry>
1029      </row>
1030
1031      <row>
1032       <entry><structfield>attinhcount</structfield></entry>
1033       <entry><type>int4</type></entry>
1034       <entry></entry>
1035       <entry>
1036        The number of direct ancestors this column has.  A column with a
1037        nonzero number of ancestors cannot be dropped nor renamed.
1038       </entry>
1039      </row>
1040
1041      <row>
1042       <entry><structfield>attacl</structfield></entry>
1043       <entry><type>aclitem[]</type></entry>
1044       <entry></entry>
1045       <entry>
1046        Column-level access privileges, if any have been granted specifically
1047        on this column
1048       </entry>
1049      </row>
1050
1051      <row>
1052       <entry><structfield>attoptions</structfield></entry>
1053       <entry><type>text[]</type></entry>
1054       <entry></entry>
1055       <entry>
1056        Attribute-level options, as <quote>keyword=value</> strings
1057       </entry>
1058      </row>
1059
1060     </tbody>
1061    </tgroup>
1062   </table>
1063
1064   <para>
1065    In a dropped column's <structname>pg_attribute</structname> entry,
1066    <structfield>atttypid</structfield> is reset to zero, but
1067    <structfield>attlen</structfield> and the other fields copied from
1068    <structname>pg_type</> are still valid.  This arrangement is needed
1069    to cope with the situation where the dropped column's data type was
1070    later dropped, and so there is no <structname>pg_type</> row anymore.
1071    <structfield>attlen</structfield> and the other fields can be used
1072    to interpret the contents of a row of the table.
1073   </para>
1074  </sect1>
1075
1076
1077  <sect1 id="catalog-pg-authid">
1078   <title><structname>pg_authid</structname></title>
1079
1080   <indexterm zone="catalog-pg-authid">
1081    <primary>pg_authid</primary>
1082   </indexterm>
1083
1084   <para>
1085    The catalog <structname>pg_authid</structname> contains information about
1086    database authorization identifiers (roles).  A role subsumes the concepts
1087    of <quote>users</> and <quote>groups</>.  A user is essentially just a
1088    role with the <structfield>rolcanlogin</> flag set.  Any role (with or
1089    without <structfield>rolcanlogin</>) can have other roles as members; see
1090    <link linkend="catalog-pg-auth-members"><structname>pg_auth_members</structname></link>.
1091   </para>
1092
1093   <para>
1094    Since this catalog contains passwords, it must not be publicly readable.
1095    <link linkend="view-pg-roles"><structname>pg_roles</structname></link>
1096    is a publicly readable view on
1097    <structname>pg_authid</structname> that blanks out the password field.
1098   </para>
1099
1100   <para>
1101    <xref linkend="user-manag"> contains detailed information about user and
1102    privilege management.
1103   </para>
1104
1105   <para>
1106    Because user identities are cluster-wide,
1107    <structname>pg_authid</structname>
1108    is shared across all databases of a cluster: there is only one
1109    copy of <structname>pg_authid</structname> per cluster, not
1110    one per database.
1111   </para>
1112
1113   <table>
1114    <title><structname>pg_authid</> Columns</title>
1115
1116    <tgroup cols="3">
1117     <thead>
1118      <row>
1119       <entry>Name</entry>
1120       <entry>Type</entry>
1121       <entry>Description</entry>
1122      </row>
1123     </thead>
1124
1125     <tbody>
1126      <row>
1127       <entry><structfield>rolname</structfield></entry>
1128       <entry><type>name</type></entry>
1129       <entry>Role name</entry>
1130      </row>
1131
1132      <row>
1133       <entry><structfield>rolsuper</structfield></entry>
1134       <entry><type>bool</type></entry>
1135       <entry>Role has superuser privileges</entry>
1136      </row>
1137
1138      <row>
1139       <entry><structfield>rolinherit</structfield></entry>
1140       <entry><type>bool</type></entry>
1141       <entry>Role automatically inherits privileges of roles it is a
1142        member of</entry>
1143      </row>
1144
1145      <row>
1146       <entry><structfield>rolcreaterole</structfield></entry>
1147       <entry><type>bool</type></entry>
1148       <entry>Role can create more roles</entry>
1149      </row>
1150
1151      <row>
1152       <entry><structfield>rolcreatedb</structfield></entry>
1153       <entry><type>bool</type></entry>
1154       <entry>Role can create databases</entry>
1155      </row>
1156
1157      <row>
1158       <entry><structfield>rolcatupdate</structfield></entry>
1159       <entry><type>bool</type></entry>
1160       <entry>
1161        Role can update system catalogs directly.  (Even a superuser cannot do
1162        this unless this column is true)
1163       </entry>
1164      </row>
1165
1166      <row>
1167       <entry><structfield>rolcanlogin</structfield></entry>
1168       <entry><type>bool</type></entry>
1169       <entry>
1170        Role can log in. That is, this role can be given as the initial
1171        session authorization identifier.
1172       </entry>
1173      </row>
1174
1175      <row>
1176       <entry><structfield>rolconnlimit</structfield></entry>
1177       <entry><type>int4</type></entry>
1178       <entry>
1179        For roles that can log in, this sets maximum number of concurrent
1180        connections this role can make.  -1 means no limit.
1181       </entry>
1182      </row>
1183
1184      <row>
1185       <entry><structfield>rolpassword</structfield></entry>
1186       <entry><type>text</type></entry>
1187       <entry>
1188        Password (possibly encrypted); null if none.  If the password is
1189        encrypted, this column will contain the string md5 followed by a
1190        32-character hexadecimal MD5 hash.  The MD5 hash will be of the
1191        user's password concatenated to their username (for example, if
1192        user joe has password xyzzy, <productname>PostgreSQL</> will store
1193        the md5 hash of xyzzyjoe).
1194       </entry>
1195      </row>
1196
1197      <row>
1198       <entry><structfield>rolvaliduntil</structfield></entry>
1199       <entry><type>timestamptz</type></entry>
1200       <entry>Password expiry time (only used for password authentication);
1201        null if no expiration</entry>
1202      </row>
1203     </tbody>
1204    </tgroup>
1205   </table>
1206
1207  </sect1>
1208
1209
1210  <sect1 id="catalog-pg-auth-members">
1211   <title><structname>pg_auth_members</structname></title>
1212
1213   <indexterm zone="catalog-pg-auth-members">
1214    <primary>pg_auth_members</primary>
1215   </indexterm>
1216
1217   <para>
1218    The catalog <structname>pg_auth_members</structname> shows the membership
1219    relations between roles.  Any non-circular set of relationships is allowed.
1220   </para>
1221
1222   <para>
1223    Because user identities are cluster-wide,
1224    <structname>pg_auth_members</structname>
1225    is shared across all databases of a cluster: there is only one
1226    copy of <structname>pg_auth_members</structname> per cluster, not
1227    one per database.
1228   </para>
1229
1230   <table>
1231    <title><structname>pg_auth_members</> Columns</title>
1232
1233    <tgroup cols="4">
1234     <thead>
1235      <row>
1236       <entry>Name</entry>
1237       <entry>Type</entry>
1238       <entry>References</entry>
1239       <entry>Description</entry>
1240      </row>
1241     </thead>
1242
1243     <tbody>
1244      <row>
1245       <entry><structfield>roleid</structfield></entry>
1246       <entry><type>oid</type></entry>
1247       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
1248       <entry>ID of a role that has a member</entry>
1249      </row>
1250
1251      <row>
1252       <entry><structfield>member</structfield></entry>
1253       <entry><type>oid</type></entry>
1254       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
1255       <entry>ID of a role that is a member of <structfield>roleid</></entry>
1256      </row>
1257
1258      <row>
1259       <entry><structfield>grantor</structfield></entry>
1260       <entry><type>oid</type></entry>
1261       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
1262       <entry>ID of the role that granted this membership</entry>
1263      </row>
1264
1265      <row>
1266       <entry><structfield>admin_option</structfield></entry>
1267       <entry><type>bool</type></entry>
1268       <entry></entry>
1269       <entry>True if <structfield>member</> can grant membership in
1270        <structfield>roleid</> to others</entry>
1271      </row>
1272     </tbody>
1273    </tgroup>
1274   </table>
1275
1276  </sect1>
1277
1278
1279  <sect1 id="catalog-pg-cast">
1280   <title><structname>pg_cast</structname></title>
1281
1282   <indexterm zone="catalog-pg-cast">
1283    <primary>pg_cast</primary>
1284   </indexterm>
1285
1286   <para>
1287    The catalog <structname>pg_cast</structname> stores data type conversion
1288    paths, both built-in paths and those defined with
1289    <xref linkend="sql-createcast">.
1290   </para>
1291
1292   <para>
1293    It should be noted that <structname>pg_cast</structname> does not represent
1294    every type conversion that the system knows how to perform; only those that
1295    cannot be deduced from some generic rule.  For example, casting between a
1296    domain and its base type is not explicitly represented in
1297    <structname>pg_cast</structname>.  Another important exception is that
1298    <quote>automatic I/O conversion casts</>, those performed using a data
1299    type's own I/O functions to convert to or from <type>text</> or other
1300    string types, are not explicitly represented in
1301    <structname>pg_cast</structname>.
1302   </para>
1303
1304   <table>
1305    <title><structname>pg_cast</> Columns</title>
1306
1307    <tgroup cols="4">
1308     <thead>
1309      <row>
1310       <entry>Name</entry>
1311       <entry>Type</entry>
1312       <entry>References</entry>
1313       <entry>Description</entry>
1314      </row>
1315     </thead>
1316
1317     <tbody>
1318      <row>
1319       <entry><structfield>castsource</structfield></entry>
1320       <entry><type>oid</type></entry>
1321       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
1322       <entry>OID of the source data type</entry>
1323      </row>
1324
1325      <row>
1326       <entry><structfield>casttarget</structfield></entry>
1327       <entry><type>oid</type></entry>
1328       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
1329       <entry>OID of the target data type</entry>
1330      </row>
1331
1332      <row>
1333       <entry><structfield>castfunc</structfield></entry>
1334       <entry><type>oid</type></entry>
1335       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
1336       <entry>
1337        The OID of the function to use to perform this cast.  Zero is
1338        stored if the cast method doesn't require a function.
1339       </entry>
1340      </row>
1341
1342      <row>
1343       <entry><structfield>castcontext</structfield></entry>
1344       <entry><type>char</type></entry>
1345       <entry></entry>
1346       <entry>
1347        Indicates what contexts the cast can be invoked in.
1348        <literal>e</> means only as an explicit cast (using
1349        <literal>CAST</> or <literal>::</> syntax).
1350        <literal>a</> means implicitly in assignment
1351        to a target column, as well as explicitly.
1352        <literal>i</> means implicitly in expressions, as well as the
1353        other cases.
1354       </entry>
1355      </row>
1356      <row>
1357       <entry><structfield>castmethod</structfield></entry>
1358       <entry><type>char</type></entry>
1359       <entry></entry>
1360       <entry>
1361        Indicates how the cast is performed.
1362        <literal>f</> means that the function specified in the <structfield>castfunc</> field is used.
1363        <literal>i</> means that the input/output functions are used.
1364        <literal>b</> means that the types are binary-coercible, thus no conversion is required.
1365       </entry>
1366      </row>
1367     </tbody>
1368    </tgroup>
1369   </table>
1370
1371   <para>
1372    The cast functions listed in <structname>pg_cast</structname> must
1373    always take the cast source type as their first argument type, and
1374    return the cast destination type as their result type.  A cast
1375    function can have up to three arguments.  The second argument,
1376    if present, must be type <type>integer</>; it receives the type
1377    modifier associated with the destination type, or <literal>-1</>
1378    if there is none.  The third argument,
1379    if present, must be type <type>boolean</>; it receives <literal>true</>
1380    if the cast is an explicit cast, <literal>false</> otherwise.
1381   </para>
1382
1383   <para>
1384    It is legitimate to create a <structname>pg_cast</structname> entry
1385    in which the source and target types are the same, if the associated
1386    function takes more than one argument.  Such entries represent
1387    <quote>length coercion functions</> that coerce values of the type
1388    to be legal for a particular type modifier value.
1389   </para>
1390
1391   <para>
1392    When a <structname>pg_cast</structname> entry has different source and
1393    target types and a function that takes more than one argument, it
1394    represents converting from one type to another and applying a length
1395    coercion in a single step.  When no such entry is available, coercion
1396    to a type that uses a type modifier involves two steps, one to
1397    convert between data types and a second to apply the modifier.
1398   </para>
1399  </sect1>
1400
1401  <sect1 id="catalog-pg-class">
1402   <title><structname>pg_class</structname></title>
1403
1404   <indexterm zone="catalog-pg-class">
1405    <primary>pg_class</primary>
1406   </indexterm>
1407
1408   <para>
1409    The catalog <structname>pg_class</structname> catalogs tables and most
1410    everything else that has columns or is otherwise similar to a
1411    table.  This includes indexes (but see also
1412    <structname>pg_index</structname>), sequences, views, composite types,
1413    and TOAST tables; see <structfield>relkind</>.
1414    Below, when we mean all of these
1415    kinds of objects we speak of <quote>relations</quote>.  Not all
1416    columns are meaningful for all relation types.
1417   </para>
1418
1419   <table>
1420    <title><structname>pg_class</> Columns</title>
1421
1422    <tgroup cols="4">
1423     <thead>
1424      <row>
1425       <entry>Name</entry>
1426       <entry>Type</entry>
1427       <entry>References</entry>
1428       <entry>Description</entry>
1429      </row>
1430     </thead>
1431
1432     <tbody>
1433      <row>
1434       <entry><structfield>relname</structfield></entry>
1435       <entry><type>name</type></entry>
1436       <entry></entry>
1437       <entry>Name of the table, index, view, etc.</entry>
1438      </row>
1439
1440      <row>
1441       <entry><structfield>relnamespace</structfield></entry>
1442       <entry><type>oid</type></entry>
1443       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>
1444       <entry>
1445        The OID of the namespace that contains this relation
1446       </entry>
1447      </row>
1448
1449      <row>
1450       <entry><structfield>reltype</structfield></entry>
1451       <entry><type>oid</type></entry>
1452       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
1453       <entry>
1454        The OID of the data type that corresponds to this table's row type,
1455        if any (zero for indexes, which have no <structname>pg_type</> entry)
1456       </entry>
1457      </row>
1458
1459      <row>
1460       <entry><structfield>reloftype</structfield></entry>
1461       <entry><type>oid</type></entry>
1462       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
1463       <entry>
1464        For typed tables, the OID of the underlying composite type,
1465        zero for all other relations
1466       </entry>
1467      </row>
1468
1469      <row>
1470       <entry><structfield>relowner</structfield></entry>
1471       <entry><type>oid</type></entry>
1472       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
1473       <entry>Owner of the relation</entry>
1474      </row>
1475
1476      <row>
1477       <entry><structfield>relam</structfield></entry>
1478       <entry><type>oid</type></entry>
1479       <entry><literal><link linkend="catalog-pg-am"><structname>pg_am</structname></link>.oid</literal></entry>
1480       <entry>If this is an index, the access method used (B-tree, hash, etc.)</entry>
1481      </row>
1482
1483      <row>
1484       <entry><structfield>relfilenode</structfield></entry>
1485       <entry><type>oid</type></entry>
1486       <entry></entry>
1487       <entry>Name of the on-disk file of this relation; zero means this
1488        is a <quote>mapped</> relation whose disk file name is determined
1489        by low-level state</entry>
1490      </row>
1491
1492      <row>
1493       <entry><structfield>reltablespace</structfield></entry>
1494       <entry><type>oid</type></entry>
1495       <entry><literal><link linkend="catalog-pg-tablespace"><structname>pg_tablespace</structname></link>.oid</literal></entry>
1496       <entry>
1497        The tablespace in which this relation is stored.  If zero,
1498        the database's default tablespace is implied.  (Not meaningful
1499        if the relation has no on-disk file.)
1500       </entry>
1501      </row>
1502
1503      <row>
1504       <entry><structfield>relpages</structfield></entry>
1505       <entry><type>int4</type></entry>
1506       <entry></entry>
1507       <entry>
1508        Size of the on-disk representation of this table in pages (of size
1509        <symbol>BLCKSZ</symbol>).  This is only an estimate used by the
1510        planner.  It is updated by <command>VACUUM</command>,
1511        <command>ANALYZE</command>, and a few DDL commands such as
1512        <command>CREATE INDEX</command>.
1513       </entry>
1514      </row>
1515
1516      <row>
1517       <entry><structfield>reltuples</structfield></entry>
1518       <entry><type>float4</type></entry>
1519       <entry></entry>
1520       <entry>
1521        Number of rows in the table.  This is only an estimate used by the
1522        planner.  It is updated by <command>VACUUM</command>,
1523        <command>ANALYZE</command>, and a few DDL commands such as
1524        <command>CREATE INDEX</command>.
1525       </entry>
1526      </row>
1527
1528      <row>
1529       <entry><structfield>reltoastrelid</structfield></entry>
1530       <entry><type>oid</type></entry>
1531       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
1532       <entry>
1533        OID of the TOAST table associated with this table, 0 if none.  The
1534        TOAST table stores large attributes <quote>out of line</quote> in a
1535        secondary table.
1536       </entry>
1537      </row>
1538
1539      <row>
1540       <entry><structfield>reltoastidxid</structfield></entry>
1541       <entry><type>oid</type></entry>
1542       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
1543       <entry>
1544        For a TOAST table, the OID of its index.  0 if not a TOAST table.
1545       </entry>
1546      </row>
1547
1548      <row>
1549       <entry><structfield>relhasindex</structfield></entry>
1550       <entry><type>bool</type></entry>
1551       <entry></entry>
1552       <entry>
1553        True if this is a table and it has (or recently had) any indexes
1554       </entry>
1555      </row>
1556
1557      <row>
1558       <entry><structfield>relisshared</structfield></entry>
1559       <entry><type>bool</type></entry>
1560       <entry></entry>
1561       <entry>
1562        True if this table is shared across all databases in the cluster.  Only
1563        certain system catalogs (such as <structname>pg_database</structname>)
1564        are shared.
1565       </entry>
1566      </row>
1567
1568      <row>
1569       <entry><structfield>relistemp</structfield></entry>
1570       <entry><type>bool</type></entry>
1571       <entry></entry>
1572       <entry>
1573        True if this table is a temporary relation.  If so, only the creating
1574        session can safely access its contents.
1575       </entry>
1576      </row>
1577
1578      <row>
1579       <entry><structfield>relkind</structfield></entry>
1580       <entry><type>char</type></entry>
1581       <entry></entry>
1582       <entry>
1583        <literal>r</> = ordinary table, <literal>i</> = index,
1584        <literal>S</> = sequence, <literal>v</> = view, <literal>c</> =
1585        composite type, <literal>t</> = TOAST table,
1586        <literal>f</> = foiregn table
1587       </entry>
1588      </row>
1589
1590      <row>
1591       <entry><structfield>relnatts</structfield></entry>
1592       <entry><type>int2</type></entry>
1593       <entry></entry>
1594       <entry>
1595        Number of user columns in the relation (system columns not
1596        counted).  There must be this many corresponding entries in
1597        <structname>pg_attribute</structname>.  See also
1598        <literal>pg_attribute.attnum</literal>.
1599       </entry>
1600      </row>
1601
1602      <row>
1603       <entry><structfield>relchecks</structfield></entry>
1604       <entry><type>int2</type></entry>
1605       <entry></entry>
1606       <entry>
1607        Number of <literal>CHECK</> constraints on the table; see
1608        <link linkend="catalog-pg-constraint"><structname>pg_constraint</structname></link> catalog
1609       </entry>
1610      </row>
1611
1612      <row>
1613       <entry><structfield>relhasoids</structfield></entry>
1614       <entry><type>bool</type></entry>
1615       <entry></entry>
1616       <entry>
1617        True if we generate an OID for each row of the relation
1618       </entry>
1619      </row>
1620
1621      <row>
1622       <entry><structfield>relhaspkey</structfield></entry>
1623       <entry><type>bool</type></entry>
1624       <entry></entry>
1625       <entry>
1626        True if the table has (or once had) a primary key
1627       </entry>
1628      </row>
1629
1630      <row>
1631       <entry><structfield>relhasexclusion</structfield></entry>
1632       <entry><type>bool</type></entry>
1633       <entry></entry>
1634       <entry>
1635        For a table, true if the table has (or once had) any exclusion
1636        constraints; for an index, true if the index supports an exclusion
1637        constraint
1638       </entry>
1639      </row>
1640
1641      <row>
1642       <entry><structfield>relhasrules</structfield></entry>
1643       <entry><type>bool</type></entry>
1644       <entry></entry>
1645       <entry>
1646        True if table has (or once had) rules; see
1647        <link linkend="catalog-pg-rewrite"><structname>pg_rewrite</structname></link> catalog
1648       </entry>
1649      </row>
1650
1651      <row>
1652       <entry><structfield>relhastriggers</structfield></entry>
1653       <entry><type>bool</type></entry>
1654       <entry></entry>
1655       <entry>
1656        True if table has (or once had) triggers; see
1657        <link linkend="catalog-pg-trigger"><structname>pg_trigger</structname></link> catalog
1658       </entry>
1659      </row>
1660
1661      <row>
1662       <entry><structfield>relhassubclass</structfield></entry>
1663       <entry><type>bool</type></entry>
1664       <entry></entry>
1665       <entry>True if table has (or once had) any inheritance children</entry>
1666      </row>
1667
1668      <row>
1669       <entry><structfield>relfrozenxid</structfield></entry>
1670       <entry><type>xid</type></entry>
1671       <entry></entry>
1672       <entry>
1673        All transaction IDs before this one have been replaced with a permanent
1674        (<quote>frozen</>) transaction ID in this table.  This is used to track
1675        whether the table needs to be vacuumed in order to prevent transaction
1676        ID wraparound or to allow <literal>pg_clog</> to be shrunk.  Zero
1677        (<symbol>InvalidTransactionId</symbol>) if the relation is not a table.
1678       </entry>
1679      </row>
1680
1681      <row>
1682       <entry><structfield>relacl</structfield></entry>
1683       <entry><type>aclitem[]</type></entry>
1684       <entry></entry>
1685       <entry>
1686        Access privileges; see
1687        <xref linkend="sql-grant"> and
1688        <xref linkend="sql-revoke">
1689        for details
1690       </entry>
1691      </row>
1692
1693      <row>
1694       <entry><structfield>reloptions</structfield></entry>
1695       <entry><type>text[]</type></entry>
1696       <entry></entry>
1697       <entry>
1698        Access-method-specific options, as <quote>keyword=value</> strings
1699       </entry>
1700      </row>
1701     </tbody>
1702    </tgroup>
1703   </table>
1704
1705   <para>
1706    Several of the Boolean flags in <structname>pg_class</> are maintained
1707    lazily: they are guaranteed to be true if that's the correct state, but
1708    may not be reset to false immediately when the condition is no longer
1709    true.  For example, <structfield>relhasindex</> is set by
1710    <command>CREATE INDEX</command>, but it is never cleared by
1711    <command>DROP INDEX</command>.  Instead, <command>VACUUM</command> clears
1712    <structfield>relhasindex</> if it finds the table has no indexes.  This
1713    arrangement avoids race conditions and improves concurrency.
1714   </para>
1715  </sect1>
1716
1717  <sect1 id="catalog-pg-constraint">
1718   <title><structname>pg_constraint</structname></title>
1719
1720   <indexterm zone="catalog-pg-constraint">
1721    <primary>pg_constraint</primary>
1722   </indexterm>
1723
1724   <para>
1725    The catalog <structname>pg_constraint</structname> stores check, primary
1726    key, unique, foreign key, and exclusion constraints on tables.
1727    (Column constraints are not treated specially.  Every column constraint is
1728    equivalent to some table constraint.)
1729    Not-null constraints are represented in the <structname>pg_attribute</>
1730    catalog, not here.
1731   </para>
1732
1733   <para>
1734    User-defined constraint triggers (created with <command>CREATE CONSTRAINT
1735    TRIGGER</>) also give rise to an entry in this table.
1736   </para>
1737
1738   <para>
1739    Check constraints on domains are stored here, too.
1740   </para>
1741
1742   <table>
1743    <title><structname>pg_constraint</> Columns</title>
1744
1745    <tgroup cols="4">
1746     <thead>
1747      <row>
1748       <entry>Name</entry>
1749       <entry>Type</entry>
1750       <entry>References</entry>
1751       <entry>Description</entry>
1752      </row>
1753     </thead>
1754
1755     <tbody>
1756      <row>
1757       <entry><structfield>conname</structfield></entry>
1758       <entry><type>name</type></entry>
1759       <entry></entry>
1760       <entry>Constraint name (not necessarily unique!)</entry>
1761      </row>
1762
1763      <row>
1764       <entry><structfield>connamespace</structfield></entry>
1765       <entry><type>oid</type></entry>
1766       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>
1767       <entry>
1768        The OID of the namespace that contains this constraint
1769       </entry>
1770      </row>
1771
1772      <row>
1773       <entry><structfield>contype</structfield></entry>
1774       <entry><type>char</type></entry>
1775       <entry></entry>
1776       <entry>
1777         <literal>c</> = check constraint,
1778         <literal>f</> = foreign key constraint,
1779         <literal>p</> = primary key constraint,
1780         <literal>u</> = unique constraint,
1781         <literal>t</> = constraint trigger,
1782         <literal>x</> = exclusion constraint
1783       </entry>
1784      </row>
1785
1786      <row>
1787       <entry><structfield>condeferrable</structfield></entry>
1788       <entry><type>bool</type></entry>
1789       <entry></entry>
1790       <entry>Is the constraint deferrable?</entry>
1791      </row>
1792
1793      <row>
1794       <entry><structfield>condeferred</structfield></entry>
1795       <entry><type>bool</type></entry>
1796       <entry></entry>
1797       <entry>Is the constraint deferred by default?</entry>
1798      </row>
1799
1800      <row>
1801       <entry><structfield>conrelid</structfield></entry>
1802       <entry><type>oid</type></entry>
1803       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
1804       <entry>The table this constraint is on; 0 if not a table constraint</entry>
1805      </row>
1806
1807      <row>
1808       <entry><structfield>contypid</structfield></entry>
1809       <entry><type>oid</type></entry>
1810       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
1811       <entry>The domain this constraint is on; 0 if not a domain constraint</entry>
1812      </row>
1813
1814      <row>
1815       <entry><structfield>conindid</structfield></entry>
1816       <entry><type>oid</type></entry>
1817       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
1818       <entry>The index supporting this constraint, if it's a unique, primary
1819        key, foreign key, or exclusion constraint; else 0</entry>
1820      </row>
1821
1822      <row>
1823       <entry><structfield>confrelid</structfield></entry>
1824       <entry><type>oid</type></entry>
1825       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
1826       <entry>If a foreign key, the referenced table; else 0</entry>
1827      </row>
1828
1829      <row>
1830       <entry><structfield>confupdtype</structfield></entry>
1831       <entry><type>char</type></entry>
1832       <entry></entry>
1833       <entry>Foreign key update action code:
1834             <literal>a</> = no action,
1835             <literal>r</> = restrict,
1836             <literal>c</> = cascade,
1837             <literal>n</> = set null,
1838             <literal>d</> = set default
1839           </entry>
1840      </row>
1841
1842      <row>
1843       <entry><structfield>confdeltype</structfield></entry>
1844       <entry><type>char</type></entry>
1845       <entry></entry>
1846       <entry>Foreign key deletion action code:
1847             <literal>a</> = no action,
1848             <literal>r</> = restrict,
1849             <literal>c</> = cascade,
1850             <literal>n</> = set null,
1851             <literal>d</> = set default
1852           </entry>
1853      </row>
1854
1855      <row>
1856       <entry><structfield>confmatchtype</structfield></entry>
1857       <entry><type>char</type></entry>
1858       <entry></entry>
1859       <entry>Foreign key match type:
1860             <literal>f</> = full,
1861             <literal>p</> = partial,
1862             <literal>u</> = simple (unspecified)
1863           </entry>
1864      </row>
1865
1866      <row>
1867       <entry><structfield>conislocal</structfield></entry>
1868       <entry><type>bool</type></entry>
1869       <entry></entry>
1870       <entry>
1871        This constraint is defined locally for the relation.  Note that a
1872        constraint can be locally defined and inherited simultaneously.
1873       </entry>
1874      </row>
1875
1876      <row>
1877       <entry><structfield>coninhcount</structfield></entry>
1878       <entry><type>int4</type></entry>
1879       <entry></entry>
1880       <entry>
1881        The number of direct inheritance ancestors this constraint has.
1882        A constraint with
1883        a nonzero number of ancestors cannot be dropped nor renamed.
1884       </entry>
1885      </row>
1886
1887      <row>
1888       <entry><structfield>conkey</structfield></entry>
1889       <entry><type>int2[]</type></entry>
1890       <entry><literal><link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.attnum</></entry>
1891       <entry>If a table constraint (including foreign keys, but not constraint
1892        triggers), list of the constrained columns</entry>
1893      </row>
1894
1895      <row>
1896       <entry><structfield>confkey</structfield></entry>
1897       <entry><type>int2[]</type></entry>
1898       <entry><literal><link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.attnum</></entry>
1899       <entry>If a foreign key, list of the referenced columns</entry>
1900      </row>
1901
1902      <row>
1903       <entry><structfield>conpfeqop</structfield></entry>
1904       <entry><type>oid[]</type></entry>
1905       <entry><literal><link linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.oid</></entry>
1906       <entry>If a foreign key, list of the equality operators for PK = FK comparisons</entry>
1907      </row>
1908
1909      <row>
1910       <entry><structfield>conppeqop</structfield></entry>
1911       <entry><type>oid[]</type></entry>
1912       <entry><literal><link linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.oid</></entry>
1913       <entry>If a foreign key, list of the equality operators for PK = PK comparisons</entry>
1914      </row>
1915
1916      <row>
1917       <entry><structfield>conffeqop</structfield></entry>
1918       <entry><type>oid[]</type></entry>
1919       <entry><literal><link linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.oid</></entry>
1920       <entry>If a foreign key, list of the equality operators for FK = FK comparisons</entry>
1921      </row>
1922
1923      <row>
1924       <entry><structfield>conexclop</structfield></entry>
1925       <entry><type>oid[]</type></entry>
1926       <entry><literal><link linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.oid</></entry>
1927       <entry>If an exclusion constraint, list of the per-column exclusion operators</entry>
1928      </row>
1929
1930      <row>
1931       <entry><structfield>conbin</structfield></entry>
1932       <entry><type>pg_node_tree</type></entry>
1933       <entry></entry>
1934       <entry>If a check constraint, an internal representation of the expression</entry>
1935      </row>
1936
1937      <row>
1938       <entry><structfield>consrc</structfield></entry>
1939       <entry><type>text</type></entry>
1940       <entry></entry>
1941       <entry>If a check constraint, a human-readable representation of the expression</entry>
1942      </row>
1943     </tbody>
1944    </tgroup>
1945   </table>
1946
1947   <para>
1948    In the case of an exclusion constraint, <structfield>conkey</structfield>
1949    is only useful for constraint elements that are simple column references.
1950    For other cases, a zero appears in <structfield>conkey</structfield>
1951    and the associated index must be consulted to discover the expression
1952    that is constrained.  (<structfield>conkey</structfield> thus has the
1953    same contents as <structname>pg_index</>.<structfield>indkey</> for the
1954    index.)
1955   </para>
1956
1957   <note>
1958    <para>
1959     <structfield>consrc</structfield> is not updated when referenced objects
1960     change; for example, it won't track renaming of columns.  Rather than
1961     relying on this field, it's best to use <function>pg_get_constraintdef()</>
1962     to extract the definition of a check constraint.
1963    </para>
1964   </note>
1965
1966   <note>
1967    <para>
1968     <literal>pg_class.relchecks</literal> needs to agree with the
1969     number of check-constraint entries found in this table for each
1970     relation.  Also, <literal>pg_class.relhasexclusion</literal> must
1971     be true if there are any exclusion-constraint entries for the relation.
1972    </para>
1973   </note>
1974
1975  </sect1>
1976
1977  <sect1 id="catalog-pg-conversion">
1978   <title><structname>pg_conversion</structname></title>
1979
1980   <indexterm zone="catalog-pg-conversion">
1981    <primary>pg_conversion</primary>
1982   </indexterm>
1983
1984   <para>
1985    The catalog <structname>pg_conversion</structname> describes the
1986    available encoding conversion procedures.  See
1987    <xref linkend="sql-createconversion">
1988    for more information.
1989   </para>
1990
1991   <table>
1992    <title><structname>pg_conversion</> Columns</title>
1993
1994    <tgroup cols="4">
1995     <thead>
1996      <row>
1997       <entry>Name</entry>
1998       <entry>Type</entry>
1999       <entry>References</entry>
2000       <entry>Description</entry>
2001      </row>
2002     </thead>
2003
2004     <tbody>
2005      <row>
2006       <entry><structfield>conname</structfield></entry>
2007       <entry><type>name</type></entry>
2008       <entry></entry>
2009       <entry>Conversion name (unique within a namespace)</entry>
2010      </row>
2011
2012      <row>
2013       <entry><structfield>connamespace</structfield></entry>
2014       <entry><type>oid</type></entry>
2015       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>
2016       <entry>
2017        The OID of the namespace that contains this conversion
2018       </entry>
2019      </row>
2020
2021      <row>
2022       <entry><structfield>conowner</structfield></entry>
2023       <entry><type>oid</type></entry>
2024       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
2025       <entry>Owner of the conversion</entry>
2026      </row>
2027
2028      <row>
2029       <entry><structfield>conforencoding</structfield></entry>
2030       <entry><type>int4</type></entry>
2031       <entry></entry>
2032       <entry>Source encoding ID</entry>
2033      </row>
2034
2035      <row>
2036       <entry><structfield>contoencoding</structfield></entry>
2037       <entry><type>int4</type></entry>
2038       <entry></entry>
2039       <entry>Destination encoding ID</entry>
2040      </row>
2041
2042      <row>
2043       <entry><structfield>conproc</structfield></entry>
2044       <entry><type>regproc</type></entry>
2045       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
2046       <entry>Conversion procedure</entry>
2047      </row>
2048
2049      <row>
2050       <entry><structfield>condefault</structfield></entry>
2051       <entry><type>bool</type></entry>
2052       <entry></entry>
2053       <entry>True if this is the default conversion</entry>
2054      </row>
2055
2056     </tbody>
2057    </tgroup>
2058   </table>
2059
2060  </sect1>
2061
2062  <sect1 id="catalog-pg-database">
2063   <title><structname>pg_database</structname></title>
2064
2065   <indexterm zone="catalog-pg-database">
2066    <primary>pg_database</primary>
2067   </indexterm>
2068
2069   <para>
2070    The catalog <structname>pg_database</structname> stores information about
2071    the available databases.  Databases are created with the <xref
2072    linkend="sql-createdatabase"> command.
2073    Consult <xref linkend="managing-databases"> for details about the meaning
2074    of some of the parameters.
2075   </para>
2076
2077   <para>
2078    Unlike most system catalogs, <structname>pg_database</structname>
2079    is shared across all databases of a cluster: there is only one
2080    copy of <structname>pg_database</structname> per cluster, not
2081    one per database.
2082   </para>
2083
2084   <table>
2085    <title><structname>pg_database</> Columns</title>
2086
2087    <tgroup cols="4">
2088     <thead>
2089      <row>
2090       <entry>Name</entry>
2091       <entry>Type</entry>
2092       <entry>References</entry>
2093       <entry>Description</entry>
2094      </row>
2095     </thead>
2096
2097     <tbody>
2098      <row>
2099       <entry><structfield>datname</structfield></entry>
2100       <entry><type>name</type></entry>
2101       <entry></entry>
2102       <entry>Database name</entry>
2103      </row>
2104
2105      <row>
2106       <entry><structfield>datdba</structfield></entry>
2107       <entry><type>oid</type></entry>
2108       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
2109       <entry>Owner of the database, usually the user who created it</entry>
2110      </row>
2111
2112      <row>
2113       <entry><structfield>encoding</structfield></entry>
2114       <entry><type>int4</type></entry>
2115       <entry></entry>
2116       <entry>Character encoding for this database
2117           (<function>pg_encoding_to_char()</function> can translate
2118            this number to the encoding name)</entry>
2119      </row>
2120
2121      <row>
2122       <entry><structfield>datcollate</structfield></entry>
2123       <entry><type>name</type></entry>
2124       <entry></entry>
2125       <entry>LC_COLLATE for this database</entry>
2126      </row>
2127
2128      <row>
2129       <entry><structfield>datctype</structfield></entry>
2130       <entry><type>name</type></entry>
2131       <entry></entry>
2132       <entry>LC_CTYPE for this database</entry>
2133      </row>
2134
2135      <row>
2136       <entry><structfield>datistemplate</structfield></entry>
2137       <entry><type>bool</type></entry>
2138       <entry></entry>
2139       <entry>
2140        If true then this database can be used in the
2141        <literal>TEMPLATE</literal> clause of <command>CREATE
2142        DATABASE</command> to create a new database as a clone of
2143        this one
2144       </entry>
2145      </row>
2146
2147      <row>
2148       <entry><structfield>datallowconn</structfield></entry>
2149       <entry><type>bool</type></entry>
2150       <entry></entry>
2151       <entry>
2152        If false then no one can connect to this database.  This is
2153        used to protect the <literal>template0</> database from being altered.
2154       </entry>
2155      </row>
2156
2157      <row>
2158       <entry><structfield>datconnlimit</structfield></entry>
2159       <entry><type>int4</type></entry>
2160       <entry></entry>
2161       <entry>
2162        Sets maximum number of concurrent connections that can be made
2163        to this database.  -1 means no limit.
2164       </entry>
2165      </row>
2166
2167      <row>
2168       <entry><structfield>datlastsysoid</structfield></entry>
2169       <entry><type>oid</type></entry>
2170       <entry></entry>
2171       <entry>
2172        Last system OID in the database; useful
2173        particularly to <application>pg_dump</application>
2174       </entry>
2175      </row>
2176
2177      <row>
2178       <entry><structfield>datfrozenxid</structfield></entry>
2179       <entry><type>xid</type></entry>
2180       <entry></entry>
2181       <entry>
2182        All transaction IDs before this one have been replaced with a permanent
2183        (<quote>frozen</>) transaction ID in this database.  This is used to
2184        track whether the database needs to be vacuumed in order to prevent
2185        transaction ID wraparound or to allow <literal>pg_clog</> to be shrunk.
2186        It is the minimum of the per-table
2187        <structname>pg_class</>.<structfield>relfrozenxid</> values.
2188       </entry>
2189      </row>
2190
2191      <row>
2192       <entry><structfield>dattablespace</structfield></entry>
2193       <entry><type>oid</type></entry>
2194       <entry><literal><link linkend="catalog-pg-tablespace"><structname>pg_tablespace</structname></link>.oid</literal></entry>
2195       <entry>
2196        The default tablespace for the database.
2197        Within this database, all tables for which
2198        <structname>pg_class</>.<structfield>reltablespace</> is zero
2199        will be stored in this tablespace; in particular, all the non-shared
2200        system catalogs will be there.
2201       </entry>
2202      </row>
2203
2204      <row>
2205       <entry><structfield>datacl</structfield></entry>
2206       <entry><type>aclitem[]</type></entry>
2207       <entry></entry>
2208       <entry>
2209        Access privileges; see
2210        <xref linkend="sql-grant"> and
2211        <xref linkend="sql-revoke">
2212        for details
2213       </entry>
2214      </row>
2215     </tbody>
2216    </tgroup>
2217   </table>
2218  </sect1>
2219
2220
2221  <sect1 id="catalog-pg-default-acl">
2222   <title><structname>pg_default_acl</structname></title>
2223
2224   <indexterm zone="catalog-pg-default-acl">
2225    <primary>pg_default_acl</primary>
2226   </indexterm>
2227
2228   <para>
2229    The catalog <structname>pg_default_acl</> stores initial
2230    privileges to be assigned to newly created objects.
2231   </para>
2232
2233   <table>
2234    <title><structname>pg_default_acl</> Columns</title>
2235
2236    <tgroup cols="4">
2237     <thead>
2238      <row>
2239       <entry>Name</entry>
2240       <entry>Type</entry>
2241       <entry>References</entry>
2242       <entry>Description</entry>
2243      </row>
2244     </thead>
2245
2246     <tbody>
2247      <row>
2248       <entry><structfield>defaclrole</structfield></entry>
2249       <entry><type>oid</type></entry>
2250       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
2251       <entry>The OID of the role associated with this entry</entry>
2252      </row>
2253
2254      <row>
2255       <entry><structfield>defaclnamespace</structfield></entry>
2256       <entry><type>oid</type></entry>
2257       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>
2258       <entry>The OID of the namespace associated with this entry,
2259        or 0 if none</entry>
2260      </row>
2261
2262      <row>
2263       <entry><structfield>defaclobjtype</structfield></entry>
2264       <entry><type>char</type></entry>
2265       <entry></entry>
2266       <entry>
2267        Type of object this entry is for:
2268        <literal>r</> = relation (table, view),
2269        <literal>S</> = sequence,
2270        <literal>f</> = function
2271       </entry>
2272      </row>
2273
2274      <row>
2275       <entry><structfield>defaclacl</structfield></entry>
2276       <entry><type>aclitem[]</type></entry>
2277       <entry></entry>
2278       <entry>
2279        Access privileges that this type of object should have on creation
2280       </entry>
2281      </row>
2282     </tbody>
2283    </tgroup>
2284   </table>
2285
2286   <para>
2287    A <structname>pg_default_acl</> entry shows the initial privileges to
2288    be assigned to an object belonging to the indicated user.  There are
2289    currently two types of entry: <quote>global</> entries with
2290    <structfield>defaclnamespace</> = 0, and <quote>per-schema</> entries
2291    that reference a particular schema.  If a global entry is present then
2292    it <emphasis>overrides</> the normal hard-wired default privileges
2293    for the object type.  A per-schema entry, if present, represents privileges
2294    to be <emphasis>added to</> the global or hard-wired default privileges.
2295   </para>
2296
2297   <para>
2298    Note that when an ACL entry in another catalog is null, it is taken
2299    to represent the hard-wired default privileges for its object,
2300    <emphasis>not</> whatever might be in <structname>pg_default_acl</>
2301    at the moment.  <structname>pg_default_acl</> is only consulted during
2302    object creation.
2303   </para>
2304
2305  </sect1>
2306
2307
2308  <sect1 id="catalog-pg-depend">
2309   <title><structname>pg_depend</structname></title>
2310
2311   <indexterm zone="catalog-pg-depend">
2312    <primary>pg_depend</primary>
2313   </indexterm>
2314
2315   <para>
2316    The catalog <structname>pg_depend</structname> records the dependency
2317    relationships between database objects.  This information allows
2318    <command>DROP</> commands to find which other objects must be dropped
2319    by <command>DROP CASCADE</> or prevent dropping in the <command>DROP
2320    RESTRICT</> case.
2321   </para>
2322
2323   <para>
2324    See also <link linkend="catalog-pg-shdepend"><structname>pg_shdepend</structname></link>,
2325    which performs a similar function for dependencies involving objects
2326    that are shared across a database cluster.
2327   </para>
2328
2329   <table>
2330    <title><structname>pg_depend</> Columns</title>
2331
2332    <tgroup cols="4">
2333     <thead>
2334      <row>
2335       <entry>Name</entry>
2336       <entry>Type</entry>
2337       <entry>References</entry>
2338       <entry>Description</entry>
2339      </row>
2340     </thead>
2341
2342     <tbody>
2343      <row>
2344       <entry><structfield>classid</structfield></entry>
2345       <entry><type>oid</type></entry>
2346       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
2347       <entry>The OID of the system catalog the dependent object is in</entry>
2348      </row>
2349
2350      <row>
2351       <entry><structfield>objid</structfield></entry>
2352       <entry><type>oid</type></entry>
2353       <entry>any OID column</entry>
2354       <entry>The OID of the specific dependent object</entry>
2355      </row>
2356
2357      <row>
2358       <entry><structfield>objsubid</structfield></entry>
2359       <entry><type>int4</type></entry>
2360       <entry></entry>
2361       <entry>
2362        For a table column, this is the column number (the
2363        <structfield>objid</> and <structfield>classid</> refer to the
2364        table itself).  For all other object types, this column is
2365        zero.
2366       </entry>
2367      </row>
2368
2369      <row>
2370       <entry><structfield>refclassid</structfield></entry>
2371       <entry><type>oid</type></entry>
2372       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
2373       <entry>The OID of the system catalog the referenced object is in</entry>
2374      </row>
2375
2376      <row>
2377       <entry><structfield>refobjid</structfield></entry>
2378       <entry><type>oid</type></entry>
2379       <entry>any OID column</entry>
2380       <entry>The OID of the specific referenced object</entry>
2381      </row>
2382
2383      <row>
2384       <entry><structfield>refobjsubid</structfield></entry>
2385       <entry><type>int4</type></entry>
2386       <entry></entry>
2387       <entry>
2388        For a table column, this is the column number (the
2389        <structfield>refobjid</> and <structfield>refclassid</> refer
2390        to the table itself).  For all other object types, this column
2391        is zero.
2392       </entry>
2393      </row>
2394
2395      <row>
2396       <entry><structfield>deptype</structfield></entry>
2397       <entry><type>char</type></entry>
2398       <entry></entry>
2399       <entry>
2400        A code defining the specific semantics of this dependency relationship; see text
2401       </entry>
2402      </row>
2403
2404     </tbody>
2405    </tgroup>
2406   </table>
2407
2408   <para>
2409    In all cases, a <structname>pg_depend</structname> entry indicates that the
2410    referenced object cannot be dropped without also dropping the dependent
2411    object.  However, there are several subflavors identified by
2412    <structfield>deptype</>:
2413
2414    <variablelist>
2415     <varlistentry>
2416      <term><symbol>DEPENDENCY_NORMAL</> (<literal>n</>)</term>
2417      <listitem>
2418       <para>
2419        A normal relationship between separately-created objects.  The
2420        dependent object can be dropped without affecting the
2421        referenced object.  The referenced object can only be dropped
2422        by specifying <literal>CASCADE</>, in which case the dependent
2423        object is dropped, too.  Example: a table column has a normal
2424        dependency on its data type.
2425       </para>
2426      </listitem>
2427     </varlistentry>
2428
2429     <varlistentry>
2430      <term><symbol>DEPENDENCY_AUTO</> (<literal>a</>)</term>
2431      <listitem>
2432       <para>
2433        The dependent object can be dropped separately from the
2434        referenced object, and should be automatically dropped
2435        (regardless of <literal>RESTRICT</> or <literal>CASCADE</>
2436        mode) if the referenced object is dropped.  Example: a named
2437        constraint on a table is made autodependent on the table, so
2438        that it will go away if the table is dropped.
2439       </para>
2440      </listitem>
2441     </varlistentry>
2442
2443     <varlistentry>
2444      <term><symbol>DEPENDENCY_INTERNAL</> (<literal>i</>)</term>
2445      <listitem>
2446       <para>
2447        The dependent object was created as part of creation of the
2448        referenced object, and is really just a part of its internal
2449        implementation.  A <command>DROP</> of the dependent object
2450        will be disallowed outright (we'll tell the user to issue a
2451        <command>DROP</> against the referenced object, instead).  A
2452        <command>DROP</> of the referenced object will be propagated
2453        through to drop the dependent object whether
2454        <command>CASCADE</> is specified or not.  Example: a trigger
2455        that's created to enforce a foreign-key constraint is made
2456        internally dependent on the constraint's
2457        <structname>pg_constraint</> entry.
2458       </para>
2459      </listitem>
2460     </varlistentry>
2461
2462     <varlistentry>
2463      <term><symbol>DEPENDENCY_PIN</> (<literal>p</>)</term>
2464      <listitem>
2465       <para>
2466        There is no dependent object; this type of entry is a signal
2467        that the system itself depends on the referenced object, and so
2468        that object must never be deleted.  Entries of this type are
2469        created only by <command>initdb</command>.  The columns for the
2470        dependent object contain zeroes.
2471       </para>
2472      </listitem>
2473     </varlistentry>
2474    </variablelist>
2475
2476    Other dependency flavors might be needed in future.
2477   </para>
2478
2479  </sect1>
2480
2481
2482  <sect1 id="catalog-pg-description">
2483   <title><structname>pg_description</structname></title>
2484
2485   <indexterm zone="catalog-pg-description">
2486    <primary>pg_description</primary>
2487   </indexterm>
2488
2489   <para>
2490    The catalog <structname>pg_description</> stores optional descriptions
2491    (comments) for each database object.  Descriptions can be manipulated
2492    with the <xref linkend="sql-comment"> command and viewed with
2493    <application>psql</application>'s <literal>\d</literal> commands.
2494    Descriptions of many built-in system objects are provided in the initial
2495    contents of <structname>pg_description</structname>.
2496   </para>
2497
2498   <para>
2499    See also <link linkend="catalog-pg-shdescription"><structname>pg_shdescription</structname></link>,
2500    which performs a similar function for descriptions involving objects that
2501    are shared across a database cluster.
2502   </para>
2503
2504   <table>
2505    <title><structname>pg_description</> Columns</title>
2506
2507    <tgroup cols="4">
2508     <thead>
2509      <row>
2510       <entry>Name</entry>
2511       <entry>Type</entry>
2512       <entry>References</entry>
2513       <entry>Description</entry>
2514      </row>
2515     </thead>
2516
2517     <tbody>
2518      <row>
2519       <entry><structfield>objoid</structfield></entry>
2520       <entry><type>oid</type></entry>
2521       <entry>any OID column</entry>
2522       <entry>The OID of the object this description pertains to</entry>
2523      </row>
2524
2525      <row>
2526       <entry><structfield>classoid</structfield></entry>
2527       <entry><type>oid</type></entry>
2528       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
2529       <entry>The OID of the system catalog this object appears in</entry>
2530      </row>
2531
2532      <row>
2533       <entry><structfield>objsubid</structfield></entry>
2534       <entry><type>int4</type></entry>
2535       <entry></entry>
2536       <entry>
2537        For a comment on a table column, this is the column number (the
2538        <structfield>objoid</> and <structfield>classoid</> refer to
2539        the table itself).  For all other object types, this column is
2540        zero.
2541       </entry>
2542      </row>
2543
2544      <row>
2545       <entry><structfield>description</structfield></entry>
2546       <entry><type>text</type></entry>
2547       <entry></entry>
2548       <entry>Arbitrary text that serves as the description of this object</entry>
2549      </row>
2550     </tbody>
2551    </tgroup>
2552   </table>
2553
2554  </sect1>
2555
2556
2557  <sect1 id="catalog-pg-enum">
2558   <title><structname>pg_enum</structname></title>
2559
2560   <indexterm zone="catalog-pg-enum">
2561    <primary>pg_enum</primary>
2562   </indexterm>
2563
2564   <para>
2565    The <structname>pg_enum</structname> catalog contains entries
2566    matching enum types to their associated values and labels. The
2567    internal representation of a given enum value is actually the OID
2568    of its associated row in <structname>pg_enum</structname>.  The
2569    OIDs for a particular enum type are guaranteed to be ordered in
2570    the way the type should sort, but there is no guarantee about the
2571    ordering of OIDs of unrelated enum types.
2572   </para>
2573
2574   <table>
2575    <title><structname>pg_enum</> Columns</title>
2576
2577    <tgroup cols="4">
2578     <thead>
2579      <row>
2580       <entry>Name</entry>
2581       <entry>Type</entry>
2582       <entry>References</entry>
2583       <entry>Description</entry>
2584      </row>
2585     </thead>
2586
2587     <tbody>
2588      <row>
2589       <entry><structfield>enumtypid</structfield></entry>
2590       <entry><type>oid</type></entry>
2591       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
2592       <entry>The OID of the <structname>pg_type</> entry owning this enum value</entry>
2593      </row>
2594
2595      <row>
2596       <entry><structfield>enumlabel</structfield></entry>
2597       <entry><type>name</type></entry>
2598       <entry></entry>
2599       <entry>The textual label for this enum value</entry>
2600      </row>
2601     </tbody>
2602    </tgroup>
2603   </table>
2604  </sect1>
2605
2606
2607  <sect1 id="catalog-pg-foreign-data-wrapper">
2608   <title><structname>pg_foreign_data_wrapper</structname></title>
2609
2610   <indexterm zone="catalog-pg-foreign-data-wrapper">
2611    <primary>pg_foreign_data_wrapper</primary>
2612   </indexterm>
2613
2614   <para>
2615    The catalog <structname>pg_foreign_data_wrapper</structname> stores
2616    foreign-data wrapper definitions.  A foreign-data wrapper is the
2617    mechanism by which external data, residing on foreign servers, is
2618    accessed.
2619   </para>
2620
2621   <table>
2622    <title><structname>pg_foreign_data_wrapper</> Columns</title>
2623
2624    <tgroup cols="4">
2625     <thead>
2626      <row>
2627       <entry>Name</entry>
2628       <entry>Type</entry>
2629       <entry>References</entry>
2630       <entry>Description</entry>
2631      </row>
2632     </thead>
2633
2634     <tbody>
2635      <row>
2636       <entry><structfield>fdwname</structfield></entry>
2637       <entry><type>name</type></entry>
2638       <entry></entry>
2639       <entry>Name of the foreign-data wrapper</entry>
2640      </row>
2641
2642      <row>
2643       <entry><structfield>fdwowner</structfield></entry>
2644       <entry><type>oid</type></entry>
2645       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
2646       <entry>Owner of the foreign-data wrapper</entry>
2647      </row>
2648
2649      <row>
2650       <entry><structfield>fdwvalidator</structfield></entry>
2651       <entry><type>oid</type></entry>
2652       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
2653       <entry>
2654        References a validator function that is responsible for
2655        checking the validity of the generic options given to the
2656        foreign-data wrapper, as well as to foreign servers and user
2657        mappings using the foreign-data wrapper.  Zero if no validator
2658        is provided.
2659       </entry>
2660      </row>
2661
2662      <row>
2663       <entry><structfield>fdwhandler</structfield></entry>
2664       <entry><type>oid</type></entry>
2665       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
2666       <entry>
2667        References a handler function that is responsible for
2668        supplying foreign-data wrapper routines.
2669        Zero if no handler is provided.
2670       </entry>
2671      </row>
2672
2673      <row>
2674       <entry><structfield>fdwacl</structfield></entry>
2675       <entry><type>aclitem[]</type></entry>
2676       <entry></entry>
2677       <entry>
2678        Access privileges; see
2679        <xref linkend="sql-grant"> and
2680        <xref linkend="sql-revoke">
2681        for details
2682       </entry>
2683      </row>
2684
2685      <row>
2686       <entry><structfield>fdwoptions</structfield></entry>
2687       <entry><type>text[]</type></entry>
2688       <entry></entry>
2689       <entry>
2690        Foreign-data wrapper specific options, as <quote>keyword=value</> strings
2691       </entry>
2692      </row>
2693     </tbody>
2694    </tgroup>
2695   </table>
2696  </sect1>
2697
2698
2699  <sect1 id="catalog-pg-foreign-server">
2700   <title><structname>pg_foreign_server</structname></title>
2701
2702   <indexterm zone="catalog-pg-foreign-server">
2703    <primary>pg_foreign_server</primary>
2704   </indexterm>
2705
2706   <para>
2707    The catalog <structname>pg_foreign_server</structname> stores
2708    foreign server definitions.  A foreign server describes the
2709    connection to a remote server, managing external data.  Foreign
2710    servers are accessed via foreign-data wrappers.
2711   </para>
2712
2713   <table>
2714    <title><structname>pg_foreign_server</> Columns</title>
2715
2716    <tgroup cols="4">
2717     <thead>
2718      <row>
2719       <entry>Name</entry>
2720       <entry>Type</entry>
2721       <entry>References</entry>
2722       <entry>Description</entry>
2723      </row>
2724     </thead>
2725
2726     <tbody>
2727      <row>
2728       <entry><structfield>srvname</structfield></entry>
2729       <entry><type>name</type></entry>
2730       <entry></entry>
2731       <entry>Name of the foreign server</entry>
2732      </row>
2733
2734      <row>
2735       <entry><structfield>srvowner</structfield></entry>
2736       <entry><type>oid</type></entry>
2737       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
2738       <entry>Owner of the foreign server</entry>
2739      </row>
2740
2741      <row>
2742       <entry><structfield>srvfdw</structfield></entry>
2743       <entry><type>oid</type></entry>
2744       <entry><literal><link linkend="catalog-pg-foreign-data-wrapper"><structname>pg_foreign_data_wrapper</structname></link>.oid</literal></entry>
2745       <entry>The OID of the foreign-data wrapper of this foreign server</entry>
2746      </row>
2747
2748      <row>
2749       <entry><structfield>srvtype</structfield></entry>
2750       <entry><type>text</type></entry>
2751       <entry></entry>
2752       <entry>Type of the server (optional)</entry>
2753      </row>
2754
2755      <row>
2756       <entry><structfield>srvversion</structfield></entry>
2757       <entry><type>text</type></entry>
2758       <entry></entry>
2759       <entry>Version of the server (optional)</entry>
2760      </row>
2761
2762      <row>
2763       <entry><structfield>srvacl</structfield></entry>
2764       <entry><type>aclitem[]</type></entry>
2765       <entry></entry>
2766       <entry>
2767        Access privileges; see
2768        <xref linkend="sql-grant"> and
2769        <xref linkend="sql-revoke">
2770        for details
2771       </entry>
2772      </row>
2773
2774      <row>
2775       <entry><structfield>srvoptions</structfield></entry>
2776       <entry><type>text[]</type></entry>
2777       <entry></entry>
2778       <entry>
2779        Foreign server specific options, as <quote>keyword=value</> strings
2780       </entry>
2781      </row>
2782     </tbody>
2783    </tgroup>
2784   </table>
2785  </sect1>
2786
2787
2788  <sect1 id="catalog-pg-foreign-table">
2789   <title><structname>pg_foreign_table</structname></title>
2790
2791   <indexterm zone="catalog-pg-foreign-table">
2792    <primary>pg_foreign_table</primary>
2793   </indexterm>
2794
2795   <para>
2796    The catalog <structname>pg_foreign_table</structname> contains part
2797    of the information about foreign tables.
2798    The rest is mostly in <structname>pg_class</structname>.
2799   </para>
2800
2801   <table>
2802    <title><structname>pg_foreign_table</> Columns</title>
2803
2804    <tgroup cols="4">
2805     <thead>
2806      <row>
2807       <entry>Name</entry>
2808       <entry>Type</entry>
2809       <entry>References</entry>
2810       <entry>Description</entry>
2811      </row>
2812     </thead>
2813
2814     <tbody>
2815      <row>
2816       <entry><structfield>ftrelid</structfield></entry>
2817       <entry><type>oid</type></entry>
2818       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
2819       <entry>The OID of the <structname>pg_class</> entry for this foreign table</entry>
2820      </row>
2821
2822      <row>
2823       <entry><structfield>ftserver</structfield></entry>
2824       <entry><type>oid</type></entry>
2825       <entry><literal><link linkend="catalog-pg-foreign-server"><structname>pg_foreign_server</structname></link>.oid</literal></entry>
2826       <entry>The OID of the foreign server for this foreign table</entry>
2827      </row>
2828
2829      <row>
2830       <entry><structfield>srvoptions</structfield></entry>
2831       <entry><type>text[]</type></entry>
2832       <entry></entry>
2833       <entry>
2834        Foreign table specific options, as <quote>keyword=value</> strings.
2835       </entry>
2836      </row>
2837     </tbody>
2838    </tgroup>
2839   </table>
2840  </sect1>
2841
2842
2843  <sect1 id="catalog-pg-index">
2844   <title><structname>pg_index</structname></title>
2845
2846   <indexterm zone="catalog-pg-index">
2847    <primary>pg_index</primary>
2848   </indexterm>
2849
2850   <para>
2851    The catalog <structname>pg_index</structname> contains part of the information
2852    about indexes.  The rest is mostly in
2853    <structname>pg_class</structname>.
2854   </para>
2855
2856   <table>
2857    <title><structname>pg_index</> Columns</title>
2858
2859    <tgroup cols="4">
2860     <thead>
2861      <row>
2862       <entry>Name</entry>
2863       <entry>Type</entry>
2864       <entry>References</entry>
2865       <entry>Description</entry>
2866      </row>
2867     </thead>
2868
2869     <tbody>
2870      <row>
2871       <entry><structfield>indexrelid</structfield></entry>
2872       <entry><type>oid</type></entry>
2873       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
2874       <entry>The OID of the <structname>pg_class</> entry for this index</entry>
2875      </row>
2876
2877      <row>
2878       <entry><structfield>indrelid</structfield></entry>
2879       <entry><type>oid</type></entry>
2880       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
2881       <entry>The OID of the <structname>pg_class</> entry for the table this index is for</entry>
2882      </row>
2883
2884      <row>
2885       <entry><structfield>indnatts</structfield></entry>
2886       <entry><type>int2</type></entry>
2887       <entry></entry>
2888       <entry>The number of columns in the index (duplicates
2889       <literal>pg_class.relnatts</literal>)</entry>
2890      </row>
2891
2892      <row>
2893       <entry><structfield>indisunique</structfield></entry>
2894       <entry><type>bool</type></entry>
2895       <entry></entry>
2896       <entry>If true, this is a unique index</entry>
2897      </row>
2898
2899      <row>
2900       <entry><structfield>indisprimary</structfield></entry>
2901       <entry><type>bool</type></entry>
2902       <entry></entry>
2903       <entry>If true, this index represents the primary key of the table
2904       (<structfield>indisunique</> should always be true when this is true)</entry>
2905      </row>
2906
2907      <row>
2908       <entry><structfield>indimmediate</structfield></entry>
2909       <entry><type>bool</type></entry>
2910       <entry></entry>
2911       <entry>If true, the uniqueness check is enforced immediately on insertion
2912       (<structfield>indisunique</> should always be true when this is true)</entry>
2913      </row>
2914
2915      <row>
2916       <entry><structfield>indisclustered</structfield></entry>
2917       <entry><type>bool</type></entry>
2918       <entry></entry>
2919       <entry>If true, the table was last clustered on this index</entry>
2920      </row>
2921
2922      <row>
2923       <entry><structfield>indisvalid</structfield></entry>
2924       <entry><type>bool</type></entry>
2925       <entry></entry>
2926       <entry>
2927        If true, the index is currently valid for queries.  False means the
2928        index is possibly incomplete: it must still be modified by
2929        <command>INSERT</>/<command>UPDATE</> operations, but it cannot safely
2930        be used for queries. If it is unique, the uniqueness property is not
2931        true either.
2932       </entry>
2933      </row>
2934
2935      <row>
2936       <entry><structfield>indcheckxmin</structfield></entry>
2937       <entry><type>bool</type></entry>
2938       <entry></entry>
2939       <entry>
2940        If true, queries must not use the index until the <structfield>xmin</>
2941        of this <structname>pg_index</> row is below their <symbol>TransactionXmin</symbol>
2942        event horizon, because the table may contain broken HOT chains with
2943        incompatible rows that they can see
2944       </entry>
2945      </row>
2946
2947      <row>
2948       <entry><structfield>indisready</structfield></entry>
2949       <entry><type>bool</type></entry>
2950       <entry></entry>
2951       <entry>
2952        If true, the index is currently ready for inserts.  False means the
2953        index must be ignored by <command>INSERT</>/<command>UPDATE</>
2954        operations.
2955       </entry>
2956      </row>
2957
2958      <row>
2959       <entry><structfield>indkey</structfield></entry>
2960       <entry><type>int2vector</type></entry>
2961       <entry><literal><link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.attnum</literal></entry>
2962       <entry>
2963        This is an array of <structfield>indnatts</structfield> values that
2964        indicate which table columns this index indexes.  For example a value
2965        of <literal>1 3</literal> would mean that the first and the third table
2966        columns make up the index key.  A zero in this array indicates that the
2967        corresponding index attribute is an expression over the table columns,
2968        rather than a simple column reference.
2969       </entry>
2970      </row>
2971
2972      <row>
2973       <entry><structfield>indclass</structfield></entry>
2974       <entry><type>oidvector</type></entry>
2975       <entry><literal><link linkend="catalog-pg-opclass"><structname>pg_opclass</structname></link>.oid</literal></entry>
2976       <entry>
2977        For each column in the index key, this contains the OID of
2978        the operator class to use.  See
2979        <link linkend="catalog-pg-opclass"><structname>pg_opclass</structname></link> for details.
2980       </entry>
2981      </row>
2982
2983      <row>
2984       <entry><structfield>indoption</structfield></entry>
2985       <entry><type>int2vector</type></entry>
2986       <entry></entry>
2987       <entry>
2988        This is an array of <structfield>indnatts</structfield> values that
2989        store per-column flag bits.  The meaning of the bits is defined by
2990        the index's access method.
2991       </entry>
2992      </row>
2993
2994      <row>
2995       <entry><structfield>indexprs</structfield></entry>
2996       <entry><type>pg_node_tree</type></entry>
2997       <entry></entry>
2998       <entry>
2999        Expression trees (in <function>nodeToString()</function>
3000        representation) for index attributes that are not simple column
3001        references.  This is a list with one element for each zero
3002        entry in <structfield>indkey</>.  Null if all index attributes
3003        are simple references.
3004       </entry>
3005      </row>
3006
3007      <row>
3008       <entry><structfield>indpred</structfield></entry>
3009       <entry><type>pg_node_tree</type></entry>
3010       <entry></entry>
3011       <entry>
3012        Expression tree (in <function>nodeToString()</function>
3013        representation) for partial index predicate.  Null if not a
3014        partial index.
3015       </entry>
3016      </row>
3017     </tbody>
3018    </tgroup>
3019   </table>
3020
3021  </sect1>
3022
3023
3024  <sect1 id="catalog-pg-inherits">
3025   <title><structname>pg_inherits</structname></title>
3026
3027   <indexterm zone="catalog-pg-inherits">
3028    <primary>pg_inherits</primary>
3029   </indexterm>
3030
3031   <para>
3032    The catalog <structname>pg_inherits</> records information about
3033    table inheritance hierarchies.  There is one entry for each direct
3034    child table in the database.  (Indirect inheritance can be determined
3035    by following chains of entries.)
3036   </para>
3037
3038   <table>
3039    <title><structname>pg_inherits</> Columns</title>
3040
3041    <tgroup cols="4">
3042     <thead>
3043      <row>
3044       <entry>Name</entry>
3045       <entry>Type</entry>
3046       <entry>References</entry>
3047       <entry>Description</entry>
3048      </row>
3049     </thead>
3050
3051     <tbody>
3052      <row>
3053       <entry><structfield>inhrelid</structfield></entry>
3054       <entry><type>oid</type></entry>
3055       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
3056       <entry>
3057        The OID of the child table
3058       </entry>
3059      </row>
3060
3061      <row>
3062       <entry><structfield>inhparent</structfield></entry>
3063       <entry><type>oid</type></entry>
3064       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
3065       <entry>
3066        The OID of the parent table
3067       </entry>
3068      </row>
3069
3070      <row>
3071       <entry><structfield>inhseqno</structfield></entry>
3072       <entry><type>int4</type></entry>
3073       <entry></entry>
3074       <entry>
3075        If there is more than one direct parent for a child table (multiple
3076        inheritance), this number tells the order in which the
3077        inherited columns are to be arranged.  The count starts at 1.
3078       </entry>
3079      </row>
3080     </tbody>
3081    </tgroup>
3082   </table>
3083
3084  </sect1>
3085
3086
3087  <sect1 id="catalog-pg-language">
3088   <title><structname>pg_language</structname></title>
3089
3090   <indexterm zone="catalog-pg-language">
3091    <primary>pg_language</primary>
3092   </indexterm>
3093
3094   <para>
3095    The catalog <structname>pg_language</structname> registers
3096    languages in which you can write functions or stored procedures.
3097    See <xref linkend="sql-createlanguage">
3098    and <xref linkend="xplang"> for more information about language handlers.
3099   </para>
3100
3101   <table>
3102    <title><structname>pg_language</> Columns</title>
3103
3104    <tgroup cols="4">
3105     <thead>
3106      <row>
3107       <entry>Name</entry>
3108       <entry>Type</entry>
3109       <entry>References</entry>
3110       <entry>Description</entry>
3111      </row>
3112     </thead>
3113
3114     <tbody>
3115      <row>
3116       <entry><structfield>lanname</structfield></entry>
3117       <entry><type>name</type></entry>
3118       <entry></entry>
3119       <entry>Name of the language</entry>
3120      </row>
3121
3122      <row>
3123       <entry><structfield>lanowner</structfield></entry>
3124       <entry><type>oid</type></entry>
3125       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
3126       <entry>Owner of the language</entry>
3127      </row>
3128
3129      <row>
3130       <entry><structfield>lanispl</structfield></entry>
3131       <entry><type>bool</type></entry>
3132       <entry></entry>
3133       <entry>
3134        This is false for internal languages (such as
3135        <acronym>SQL</acronym>) and true for user-defined languages.
3136        Currently, <application>pg_dump</application> still uses this
3137        to determine which languages need to be dumped, but this might be
3138        replaced by a different mechanism in the future.
3139       </entry>
3140      </row>
3141
3142      <row>
3143       <entry><structfield>lanpltrusted</structfield></entry>
3144       <entry><type>bool</type></entry>
3145       <entry></entry>
3146       <entry>
3147        True if this is a trusted language, which means that it is believed
3148        not to grant access to anything outside the normal SQL execution
3149        environment.  Only superusers can create functions in untrusted
3150        languages.
3151       </entry>
3152      </row>
3153
3154      <row>
3155       <entry><structfield>lanplcallfoid</structfield></entry>
3156       <entry><type>oid</type></entry>
3157       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
3158       <entry>
3159        For noninternal languages this references the language
3160        handler, which is a special function that is responsible for
3161        executing all functions that are written in the particular
3162        language
3163       </entry>
3164      </row>
3165
3166      <row>
3167       <entry><structfield>laninline</structfield></entry>
3168       <entry><type>oid</type></entry>
3169       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
3170       <entry>
3171        This references a function that is responsible for executing
3172        <quote>inline</> anonymous code blocks
3173        (<xref linkend="sql-do"> blocks).
3174        Zero if inline blocks are not supported.
3175       </entry>
3176      </row>
3177
3178      <row>
3179       <entry><structfield>lanvalidator</structfield></entry>
3180       <entry><type>oid</type></entry>
3181       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
3182       <entry>
3183        This references a language validator function that is responsible
3184        for checking the syntax and validity of new functions when they
3185        are created.  Zero if no validator is provided.
3186       </entry>
3187      </row>
3188
3189      <row>
3190       <entry><structfield>lanacl</structfield></entry>
3191       <entry><type>aclitem[]</type></entry>
3192       <entry></entry>
3193       <entry>
3194        Access privileges; see
3195        <xref linkend="sql-grant"> and
3196        <xref linkend="sql-revoke">
3197        for details
3198       </entry>
3199      </row>
3200     </tbody>
3201    </tgroup>
3202   </table>
3203
3204  </sect1>
3205
3206
3207  <sect1 id="catalog-pg-largeobject">
3208   <title><structname>pg_largeobject</structname></title>
3209
3210   <indexterm zone="catalog-pg-largeobject">
3211    <primary>pg_largeobject</primary>
3212   </indexterm>
3213
3214   <para>
3215    The catalog <structname>pg_largeobject</structname> holds the data making up
3216    <quote>large objects</quote>.  A large object is identified by an OID
3217    assigned when it is created.  Each large object is broken into
3218    segments or <quote>pages</> small enough to be conveniently stored as rows
3219    in <structname>pg_largeobject</structname>.
3220    The amount of data per page is defined to be <symbol>LOBLKSIZE</> (which is currently
3221    <literal>BLCKSZ/4</>, or typically 2 kB).
3222   </para>
3223
3224   <para>
3225    Prior to <productname>PostgreSQL</> 9.0, there was no permission structure
3226    associated with large objects.  As a result,
3227    <structname>pg_largeobject</structname> was publicly readable and could be
3228    used to obtain the OIDs (and contents) of all large objects in the system.
3229    This is no longer the case; use
3230    <link linkend="catalog-pg-largeobject-metadata"><structname>pg_largeobject_metadata</></link>
3231    to obtain a list of large object OIDs.
3232   </para>
3233
3234   <table>
3235    <title><structname>pg_largeobject</> Columns</title>
3236
3237    <tgroup cols="4">
3238     <thead>
3239      <row>
3240       <entry>Name</entry>
3241       <entry>Type</entry>
3242       <entry>References</entry>
3243       <entry>Description</entry>
3244      </row>
3245     </thead>
3246
3247     <tbody>
3248      <row>
3249       <entry><structfield>loid</structfield></entry>
3250       <entry><type>oid</type></entry>
3251       <entry><literal><link linkend="catalog-pg-largeobject-metadata"><structname>pg_largeobject_metadata</structname></link>.oid</literal></entry>
3252       <entry>Identifier of the large object that includes this page</entry>
3253      </row>
3254
3255      <row>
3256       <entry><structfield>pageno</structfield></entry>
3257       <entry><type>int4</type></entry>
3258       <entry></entry>
3259       <entry>Page number of this page within its large object
3260       (counting from zero)</entry>
3261      </row>
3262
3263      <row>
3264       <entry><structfield>data</structfield></entry>
3265       <entry><type>bytea</type></entry>
3266       <entry></entry>
3267       <entry>
3268        Actual data stored in the large object.
3269        This will never be more than <symbol>LOBLKSIZE</> bytes and might be less.
3270       </entry>
3271      </row>
3272     </tbody>
3273    </tgroup>
3274   </table>
3275
3276   <para>
3277    Each row of <structname>pg_largeobject</structname> holds data
3278    for one page of a large object, beginning at
3279    byte offset (<literal>pageno * LOBLKSIZE</>) within the object.  The implementation
3280    allows sparse storage: pages might be missing, and might be shorter than
3281    <literal>LOBLKSIZE</> bytes even if they are not the last page of the object.
3282    Missing regions within a large object read as zeroes.
3283   </para>
3284
3285  </sect1>
3286
3287  <sect1 id="catalog-pg-largeobject-metadata">
3288   <title><structname>pg_largeobject_metadata</structname></title>
3289
3290   <indexterm zone="catalog-pg-largeobject-metadata">
3291    <primary>pg_largeobject_metadata</primary>
3292   </indexterm>
3293
3294   <para>
3295    The catalog <structname>pg_largeobject_metadata</structname>
3296    holds metadata associated with large objects.  The actual large object
3297    data is stored in
3298    <link linkend="catalog-pg-largeobject"><structname>pg_largeobject</></link>.
3299   </para>
3300
3301   <table>
3302    <title><structname>pg_largeobject_metadata</> Columns</title>
3303
3304    <tgroup cols="4">
3305     <thead>
3306      <row>
3307       <entry>Name</entry>
3308       <entry>Type</entry>
3309       <entry>References</entry>
3310       <entry>Description</entry>
3311      </row>
3312     </thead>
3313
3314     <tbody>
3315      <row>
3316       <entry><structfield>lomowner</structfield></entry>
3317       <entry><type>oid</type></entry>
3318       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
3319       <entry>Owner of the large object</entry>
3320      </row>
3321
3322      <row>
3323       <entry><structfield>lomacl</structfield></entry>
3324       <entry><type>aclitem[]</type></entry>
3325       <entry></entry>
3326       <entry>
3327        Access privileges; see
3328        <xref linkend="sql-grant"> and
3329        <xref linkend="sql-revoke">
3330        for details
3331       </entry>
3332      </row>
3333
3334     </tbody>
3335    </tgroup>
3336   </table>
3337  </sect1>
3338
3339  <sect1 id="catalog-pg-namespace">
3340   <title><structname>pg_namespace</structname></title>
3341
3342   <indexterm zone="catalog-pg-namespace">
3343    <primary>pg_namespace</primary>
3344   </indexterm>
3345
3346   <para>
3347    The catalog <structname>pg_namespace</> stores namespaces.
3348    A namespace is the structure underlying SQL schemas: each namespace
3349    can have a separate collection of relations, types, etc. without name
3350    conflicts.
3351   </para>
3352
3353   <table>
3354    <title><structname>pg_namespace</> Columns</title>
3355
3356    <tgroup cols="4">
3357     <thead>
3358      <row>
3359       <entry>Name</entry>
3360       <entry>Type</entry>
3361       <entry>References</entry>
3362       <entry>Description</entry>
3363      </row>
3364     </thead>
3365
3366     <tbody>
3367      <row>
3368       <entry><structfield>nspname</structfield></entry>
3369       <entry><type>name</type></entry>
3370       <entry></entry>
3371       <entry>Name of the namespace</entry>
3372      </row>
3373
3374      <row>
3375       <entry><structfield>nspowner</structfield></entry>
3376       <entry><type>oid</type></entry>
3377       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
3378       <entry>Owner of the namespace</entry>
3379      </row>
3380
3381      <row>
3382       <entry><structfield>nspacl</structfield></entry>
3383       <entry><type>aclitem[]</type></entry>
3384       <entry></entry>
3385       <entry>
3386        Access privileges; see
3387        <xref linkend="sql-grant"> and
3388        <xref linkend="sql-revoke">
3389        for details
3390       </entry>
3391      </row>
3392     </tbody>
3393    </tgroup>
3394   </table>
3395
3396  </sect1>
3397
3398
3399  <sect1 id="catalog-pg-opclass">
3400   <title><structname>pg_opclass</structname></title>
3401
3402   <indexterm zone="catalog-pg-opclass">
3403    <primary>pg_opclass</primary>
3404   </indexterm>
3405
3406   <para>
3407    The catalog <structname>pg_opclass</structname> defines
3408    index access method operator classes.  Each operator class defines
3409    semantics for index columns of a particular data type and a particular
3410    index access method.  An operator class essentially specifies that a
3411    particular operator family is applicable to a particular indexable column
3412    data type.  The set of operators from the family that are actually usable
3413    with the indexed column are whichever ones accept the column's data type
3414    as their lefthand input.
3415   </para>
3416
3417   <para>
3418    Operator classes are described at length in <xref linkend="xindex">.
3419   </para>
3420
3421   <table>
3422    <title><structname>pg_opclass</> Columns</title>
3423
3424    <tgroup cols="4">
3425     <thead>
3426      <row>
3427       <entry>Name</entry>
3428       <entry>Type</entry>
3429       <entry>References</entry>
3430       <entry>Description</entry>
3431      </row>
3432     </thead>
3433     <tbody>
3434
3435      <row>
3436       <entry><structfield>opcmethod</structfield></entry>
3437       <entry><type>oid</type></entry>
3438       <entry><literal><link linkend="catalog-pg-am"><structname>pg_am</structname></link>.oid</literal></entry>
3439       <entry>Index access method operator class is for</entry>
3440      </row>
3441
3442      <row>
3443       <entry><structfield>opcname</structfield></entry>
3444       <entry><type>name</type></entry>
3445       <entry></entry>
3446       <entry>Name of this operator class</entry>
3447      </row>
3448
3449      <row>
3450       <entry><structfield>opcnamespace</structfield></entry>
3451       <entry><type>oid</type></entry>
3452       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>
3453       <entry>Namespace of this operator class</entry>
3454      </row>
3455
3456      <row>
3457       <entry><structfield>opcowner</structfield></entry>
3458       <entry><type>oid</type></entry>
3459       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
3460       <entry>Owner of the operator class</entry>
3461      </row>
3462
3463      <row>
3464       <entry><structfield>opcfamily</structfield></entry>
3465       <entry><type>oid</type></entry>
3466       <entry><literal><link linkend="catalog-pg-opfamily"><structname>pg_opfamily</structname></link>.oid</literal></entry>
3467       <entry>Operator family containing the operator class</entry>
3468      </row>
3469
3470      <row>
3471       <entry><structfield>opcintype</structfield></entry>
3472       <entry><type>oid</type></entry>
3473       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
3474       <entry>Data type that the operator class indexes</entry>
3475      </row>
3476
3477      <row>
3478       <entry><structfield>opcdefault</structfield></entry>
3479       <entry><type>bool</type></entry>
3480       <entry></entry>
3481       <entry>True if this operator class is the default for <structfield>opcintype</></entry>
3482      </row>
3483
3484      <row>
3485       <entry><structfield>opckeytype</structfield></entry>
3486       <entry><type>oid</type></entry>
3487       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
3488       <entry>Type of data stored in index, or zero if same as <structfield>opcintype</></entry>
3489      </row>
3490
3491     </tbody>
3492    </tgroup>
3493   </table>
3494
3495   <para>
3496    An operator class's <structfield>opcmethod</> must match the
3497    <structname>opfmethod</> of its containing operator family.
3498    Also, there must be no more than one <structname>pg_opclass</structname>
3499    row having <structname>opcdefault</> true for any given combination of
3500    <structname>opcmethod</> and <structname>opcintype</>.
3501   </para>
3502
3503  </sect1>
3504
3505
3506  <sect1 id="catalog-pg-operator">
3507   <title><structname>pg_operator</structname></title>
3508
3509   <indexterm zone="catalog-pg-operator">
3510    <primary>pg_operator</primary>
3511   </indexterm>
3512
3513   <para>
3514    The catalog <structname>pg_operator</> stores information about operators.
3515    See <xref linkend="sql-createoperator">
3516    and <xref linkend="xoper"> for more information.
3517   </para>
3518
3519   <table>
3520    <title><structname>pg_operator</> Columns</title>
3521
3522    <tgroup cols="4">
3523     <thead>
3524      <row>
3525       <entry>Name</entry>
3526       <entry>Type</entry>
3527       <entry>References</entry>
3528       <entry>Description</entry>
3529      </row>
3530     </thead>
3531
3532     <tbody>
3533      <row>
3534       <entry><structfield>oprname</structfield></entry>
3535       <entry><type>name</type></entry>
3536       <entry></entry>
3537       <entry>Name of the operator</entry>
3538      </row>
3539
3540      <row>
3541       <entry><structfield>oprnamespace</structfield></entry>
3542       <entry><type>oid</type></entry>
3543       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>
3544       <entry>
3545        The OID of the namespace that contains this operator
3546       </entry>
3547      </row>
3548
3549      <row>
3550       <entry><structfield>oprowner</structfield></entry>
3551       <entry><type>oid</type></entry>
3552       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
3553       <entry>Owner of the operator</entry>
3554      </row>
3555
3556      <row>
3557       <entry><structfield>oprkind</structfield></entry>
3558       <entry><type>char</type></entry>
3559       <entry></entry>
3560       <entry>
3561        <literal>b</> = infix (<quote>both</quote>), <literal>l</> = prefix
3562        (<quote>left</quote>), <literal>r</> = postfix (<quote>right</quote>)
3563       </entry>
3564      </row>
3565
3566      <row>
3567       <entry><structfield>oprcanmerge</structfield></entry>
3568       <entry><type>bool</type></entry>
3569       <entry></entry>
3570       <entry>This operator supports merge joins</entry>
3571      </row>
3572
3573      <row>
3574       <entry><structfield>oprcanhash</structfield></entry>
3575       <entry><type>bool</type></entry>
3576       <entry></entry>
3577       <entry>This operator supports hash joins</entry>
3578      </row>
3579
3580      <row>
3581       <entry><structfield>oprleft</structfield></entry>
3582       <entry><type>oid</type></entry>
3583       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
3584       <entry>Type of the left operand</entry>
3585      </row>
3586
3587      <row>
3588       <entry><structfield>oprright</structfield></entry>
3589       <entry><type>oid</type></entry>
3590       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
3591       <entry>Type of the right operand</entry>
3592      </row>
3593
3594      <row>
3595       <entry><structfield>oprresult</structfield></entry>
3596       <entry><type>oid</type></entry>
3597       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
3598       <entry>Type of the result</entry>
3599      </row>
3600
3601      <row>
3602       <entry><structfield>oprcom</structfield></entry>
3603       <entry><type>oid</type></entry>
3604       <entry><literal><link linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.oid</literal></entry>
3605       <entry>Commutator of this operator, if any</entry>
3606      </row>
3607
3608      <row>
3609       <entry><structfield>oprnegate</structfield></entry>
3610       <entry><type>oid</type></entry>
3611       <entry><literal><link linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.oid</literal></entry>
3612       <entry>Negator of this operator, if any</entry>
3613      </row>
3614
3615      <row>
3616       <entry><structfield>oprcode</structfield></entry>
3617       <entry><type>regproc</type></entry>
3618       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
3619       <entry>Function that implements this operator</entry>
3620      </row>
3621
3622      <row>
3623       <entry><structfield>oprrest</structfield></entry>
3624       <entry><type>regproc</type></entry>
3625       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
3626       <entry>Restriction selectivity estimation function for this operator</entry>
3627      </row>
3628
3629      <row>
3630       <entry><structfield>oprjoin</structfield></entry>
3631       <entry><type>regproc</type></entry>
3632       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
3633       <entry>Join selectivity estimation function for this operator</entry>
3634      </row>
3635     </tbody>
3636    </tgroup>
3637   </table>
3638
3639   <para>
3640    Unused column contain zeroes. For example, <structfield>oprleft</structfield>
3641    is zero for a prefix operator.
3642   </para>
3643
3644  </sect1>
3645
3646
3647  <sect1 id="catalog-pg-opfamily">
3648   <title><structname>pg_opfamily</structname></title>
3649
3650   <indexterm zone="catalog-pg-opfamily">
3651    <primary>pg_opfamily</primary>
3652   </indexterm>
3653
3654   <para>
3655    The catalog <structname>pg_opfamily</structname> defines operator families.
3656    Each operator family is a collection of operators and associated
3657    support routines that implement the semantics specified for a particular
3658    index access method.  Furthermore, the operators in a family are all
3659    <quote>compatible</>, in a way that is specified by the access method.
3660    The operator family concept allows cross-data-type operators to be used
3661    with indexes and to be reasoned about using knowledge of access method
3662    semantics.
3663   </para>
3664
3665   <para>
3666    Operator families are described at length in <xref linkend="xindex">.
3667   </para>
3668
3669   <table>
3670    <title><structname>pg_opfamily</> Columns</title>
3671
3672    <tgroup cols="4">
3673     <thead>
3674      <row>
3675       <entry>Name</entry>
3676       <entry>Type</entry>
3677       <entry>References</entry>
3678       <entry>Description</entry>
3679      </row>
3680     </thead>
3681     <tbody>
3682
3683      <row>
3684       <entry><structfield>opfmethod</structfield></entry>
3685       <entry><type>oid</type></entry>
3686       <entry><literal><link linkend="catalog-pg-am"><structname>pg_am</structname></link>.oid</literal></entry>
3687       <entry>Index access method operator family is for</entry>
3688      </row>
3689
3690      <row>
3691       <entry><structfield>opfname</structfield></entry>
3692       <entry><type>name</type></entry>
3693       <entry></entry>
3694       <entry>Name of this operator family</entry>
3695      </row>
3696
3697      <row>
3698       <entry><structfield>opfnamespace</structfield></entry>
3699       <entry><type>oid</type></entry>
3700       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>
3701       <entry>Namespace of this operator family</entry>
3702      </row>
3703
3704      <row>
3705       <entry><structfield>opfowner</structfield></entry>
3706       <entry><type>oid</type></entry>
3707       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
3708       <entry>Owner of the operator family</entry>
3709      </row>
3710
3711     </tbody>
3712    </tgroup>
3713   </table>
3714
3715   <para>
3716    The majority of the information defining an operator family is not in its
3717    <structname>pg_opfamily</structname> row, but in the associated rows in
3718    <link linkend="catalog-pg-amop"><structname>pg_amop</structname></link>,
3719    <link linkend="catalog-pg-amproc"><structname>pg_amproc</structname></link>,
3720    and
3721    <link linkend="catalog-pg-opclass"><structname>pg_opclass</structname></link>.
3722   </para>
3723
3724  </sect1>
3725
3726
3727  <sect1 id="catalog-pg-pltemplate">
3728   <title><structname>pg_pltemplate</structname></title>
3729
3730   <indexterm zone="catalog-pg-pltemplate">
3731    <primary>pg_pltemplate</primary>
3732   </indexterm>
3733
3734   <para>
3735    The catalog <structname>pg_pltemplate</structname> stores
3736    <quote>template</> information for procedural languages.
3737    A template for a language allows the language to be created in a
3738    particular database by a simple <command>CREATE LANGUAGE</> command,
3739    with no need to specify implementation details.
3740   </para>
3741
3742   <para>
3743    Unlike most system catalogs, <structname>pg_pltemplate</structname>
3744    is shared across all databases of a cluster: there is only one
3745    copy of <structname>pg_pltemplate</structname> per cluster, not
3746    one per database.  This allows the information to be accessible in
3747    each database as it is needed.
3748   </para>
3749
3750   <table>
3751    <title><structname>pg_pltemplate</> Columns</title>
3752
3753    <tgroup cols="3">
3754     <thead>
3755      <row>
3756       <entry>Name</entry>
3757       <entry>Type</entry>
3758       <entry>Description</entry>
3759      </row>
3760     </thead>
3761
3762     <tbody>
3763      <row>
3764       <entry><structfield>tmplname</structfield></entry>
3765       <entry><type>name</type></entry>
3766       <entry>Name of the language this template is for</entry>
3767      </row>
3768
3769      <row>
3770       <entry><structfield>tmpltrusted</structfield></entry>
3771       <entry><type>boolean</type></entry>
3772       <entry>True if language is considered trusted</entry>
3773      </row>
3774
3775      <row>
3776       <entry><structfield>tmpldbacreate</structfield></entry>
3777       <entry><type>boolean</type></entry>
3778       <entry>True if language may be created by a database owner</entry>
3779      </row>
3780
3781      <row>
3782       <entry><structfield>tmplhandler</structfield></entry>
3783       <entry><type>text</type></entry>
3784       <entry>Name of call handler function</entry>
3785      </row>
3786
3787      <row>
3788       <entry><structfield>tmplinline</structfield></entry>
3789       <entry><type>text</type></entry>
3790       <entry>Name of anonymous-block handler function, or null if none</entry>
3791      </row>
3792
3793      <row>
3794       <entry><structfield>tmplvalidator</structfield></entry>
3795       <entry><type>text</type></entry>
3796       <entry>Name of validator function, or null if none</entry>
3797      </row>
3798
3799      <row>
3800       <entry><structfield>tmpllibrary</structfield></entry>
3801       <entry><type>text</type></entry>
3802       <entry>Path of shared library that implements language</entry>
3803      </row>
3804
3805      <row>
3806       <entry><structfield>tmplacl</structfield></entry>
3807       <entry><type>aclitem[]</type></entry>
3808       <entry>Access privileges for template (not yet used)</entry>
3809      </row>
3810
3811     </tbody>
3812    </tgroup>
3813   </table>
3814
3815   <para>
3816    There are not currently any commands that manipulate procedural language
3817    templates; to change the built-in information, a superuser must modify
3818    the table using ordinary <command>INSERT</command>, <command>DELETE</command>,
3819    or <command>UPDATE</command> commands.  It is likely that a future
3820    release of <productname>PostgreSQL</productname> will offer
3821    commands to change the entries in a cleaner fashion.
3822   </para>
3823
3824   <para>
3825    When implemented, the <structfield>tmplacl</structfield> field will provide
3826    access control for the template itself (i.e., the right to create a
3827    language using it), not for the languages created from the template.
3828   </para>
3829
3830  </sect1>
3831
3832
3833  <sect1 id="catalog-pg-proc">
3834   <title><structname>pg_proc</structname></title>
3835
3836   <indexterm zone="catalog-pg-proc">
3837    <primary>pg_proc</primary>
3838   </indexterm>
3839
3840   <para>
3841    The catalog <structname>pg_proc</> stores information about functions (or procedures).
3842    See <xref linkend="sql-createfunction">
3843    and <xref linkend="xfunc"> for more information.
3844   </para>
3845
3846   <para>
3847    The table contains data for aggregate functions as well as plain functions.
3848    If <structfield>proisagg</structfield> is true, there should be a matching
3849    row in <structfield>pg_aggregate</structfield>.
3850   </para>
3851
3852   <table>
3853    <title><structname>pg_proc</> Columns</title>
3854
3855    <tgroup cols="4">
3856     <thead>
3857      <row>
3858       <entry>Name</entry>
3859       <entry>Type</entry>
3860       <entry>References</entry>
3861       <entry>Description</entry>
3862      </row>
3863     </thead>
3864
3865     <tbody>
3866      <row>
3867       <entry><structfield>proname</structfield></entry>
3868       <entry><type>name</type></entry>
3869       <entry></entry>
3870       <entry>Name of the function</entry>
3871      </row>
3872
3873      <row>
3874       <entry><structfield>pronamespace</structfield></entry>
3875       <entry><type>oid</type></entry>
3876       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>
3877       <entry>
3878        The OID of the namespace that contains this function
3879       </entry>
3880      </row>
3881
3882      <row>
3883       <entry><structfield>proowner</structfield></entry>
3884       <entry><type>oid</type></entry>
3885       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
3886       <entry>Owner of the function</entry>
3887      </row>
3888
3889      <row>
3890       <entry><structfield>prolang</structfield></entry>
3891       <entry><type>oid</type></entry>
3892       <entry><literal><link linkend="catalog-pg-language"><structname>pg_language</structname></link>.oid</literal></entry>
3893       <entry>Implementation language or call interface of this function</entry>
3894      </row>
3895
3896      <row>
3897       <entry><structfield>procost</structfield></entry>
3898       <entry><type>float4</type></entry>
3899       <entry></entry>
3900       <entry>Estimated execution cost (in units of
3901        <xref linkend="guc-cpu-operator-cost">); if <structfield>proretset</>,
3902        this is cost per row returned</entry>
3903      </row>
3904
3905      <row>
3906       <entry><structfield>prorows</structfield></entry>
3907       <entry><type>float4</type></entry>
3908       <entry></entry>
3909       <entry>Estimated number of result rows (zero if not <structfield>proretset</>)</entry>
3910      </row>
3911
3912      <row>
3913       <entry><structfield>provariadic</structfield></entry>
3914       <entry><type>oid</type></entry>
3915       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
3916       <entry>Data type of the variadic array parameter's elements,
3917        or zero if the function does not have a variadic parameter</entry>
3918      </row>
3919
3920      <row>
3921       <entry><structfield>proisagg</structfield></entry>
3922       <entry><type>bool</type></entry>
3923       <entry></entry>
3924       <entry>Function is an aggregate function</entry>
3925      </row>
3926
3927      <row>
3928       <entry><structfield>proiswindow</structfield></entry>
3929       <entry><type>bool</type></entry>
3930       <entry></entry>
3931       <entry>Function is a window function</entry>
3932      </row>
3933
3934      <row>
3935       <entry><structfield>prosecdef</structfield></entry>
3936       <entry><type>bool</type></entry>
3937       <entry></entry>
3938       <entry>Function is a security definer (i.e., a <quote>setuid</>
3939       function)</entry>
3940      </row>
3941
3942      <row>
3943       <entry><structfield>proisstrict</structfield></entry>
3944       <entry><type>bool</type></entry>
3945       <entry></entry>
3946       <entry>
3947        Function returns null if any call argument is null.  In that
3948        case the function won't actually be called at all.  Functions
3949        that are not <quote>strict</quote> must be prepared to handle
3950        null inputs.
3951       </entry>
3952      </row>
3953
3954      <row>
3955       <entry><structfield>proretset</structfield></entry>
3956       <entry><type>bool</type></entry>
3957       <entry></entry>
3958       <entry>Function returns a set (i.e., multiple values of the specified
3959       data type)</entry>
3960      </row>
3961
3962      <row>
3963       <entry><structfield>provolatile</structfield></entry>
3964       <entry><type>char</type></entry>
3965       <entry></entry>
3966       <entry>
3967        <structfield>provolatile</structfield> tells whether the function's
3968        result depends only on its input arguments, or is affected by outside
3969        factors.
3970        It is <literal>i</literal> for <quote>immutable</> functions,
3971        which always deliver the same result for the same inputs.
3972        It is <literal>s</literal> for <quote>stable</> functions,
3973        whose results (for fixed inputs) do not change within a scan.
3974        It is <literal>v</literal> for <quote>volatile</> functions,
3975        whose results might change at any time.  (Use <literal>v</literal> also
3976        for functions with side-effects, so that calls to them cannot get
3977        optimized away.)
3978       </entry>
3979      </row>
3980
3981      <row>
3982       <entry><structfield>pronargs</structfield></entry>
3983       <entry><type>int2</type></entry>
3984       <entry></entry>
3985       <entry>Number of input arguments</entry>
3986      </row>
3987
3988      <row>
3989       <entry><structfield>pronargdefaults</structfield></entry>
3990       <entry><type>int2</type></entry>
3991       <entry></entry>
3992       <entry>Number of arguments that have defaults</entry>
3993      </row>
3994
3995      <row>
3996       <entry><structfield>prorettype</structfield></entry>
3997       <entry><type>oid</type></entry>
3998       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
3999       <entry>Data type of the return value</entry>
4000      </row>
4001
4002      <row>
4003       <entry><structfield>proargtypes</structfield></entry>
4004       <entry><type>oidvector</type></entry>
4005       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
4006       <entry>
4007        An array with the data types of the function arguments.  This includes
4008        only input arguments (including <literal>INOUT</literal> and
4009        <literal>VARIADIC</> arguments), and thus represents
4010        the call signature of the function.
4011       </entry>
4012      </row>
4013
4014      <row>
4015       <entry><structfield>proallargtypes</structfield></entry>
4016       <entry><type>oid[]</type></entry>
4017       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
4018       <entry>
4019        An array with the data types of the function arguments.  This includes
4020        all arguments (including <literal>OUT</literal> and
4021        <literal>INOUT</literal> arguments); however, if all the
4022        arguments are <literal>IN</literal> arguments, this field will be null.
4023        Note that subscripting is 1-based, whereas for historical reasons
4024        <structfield>proargtypes</> is subscripted from 0.
4025       </entry>
4026      </row>
4027
4028      <row>
4029       <entry><structfield>proargmodes</structfield></entry>
4030       <entry><type>char[]</type></entry>
4031       <entry></entry>
4032       <entry>
4033         An array with the modes of the function arguments, encoded as
4034         <literal>i</literal> for <literal>IN</> arguments,
4035         <literal>o</literal> for <literal>OUT</> arguments,
4036         <literal>b</literal> for <literal>INOUT</> arguments,
4037         <literal>v</literal> for <literal>VARIADIC</> arguments,
4038         <literal>t</literal> for <literal>TABLE</> arguments.
4039         If all the arguments are <literal>IN</literal> arguments,
4040         this field will be null.
4041         Note that subscripts correspond to positions of
4042         <structfield>proallargtypes</> not <structfield>proargtypes</>.
4043       </entry>
4044      </row>
4045
4046      <row>
4047       <entry><structfield>proargnames</structfield></entry>
4048       <entry><type>text[]</type></entry>
4049       <entry></entry>
4050       <entry>
4051         An array with the names of the function arguments.
4052         Arguments without a name are set to empty strings in the array.
4053         If none of the arguments have a name, this field will be null.
4054         Note that subscripts correspond to positions of
4055         <structfield>proallargtypes</> not <structfield>proargtypes</>.
4056       </entry>
4057      </row>
4058
4059      <row>
4060       <entry><structfield>proargdefaults</structfield></entry>
4061       <entry><type>pg_node_tree</type></entry>
4062       <entry></entry>
4063       <entry>
4064        Expression trees (in <function>nodeToString()</function> representation)
4065        for default values.  This is a list with
4066        <structfield>pronargdefaults</> elements, corresponding to the last
4067        <replaceable>N</> <emphasis>input</> arguments (i.e., the last
4068        <replaceable>N</> <structfield>proargtypes</> positions).
4069        If none of the arguments have defaults, this field will be null.
4070       </entry>
4071      </row>
4072
4073      <row>
4074       <entry><structfield>prosrc</structfield></entry>
4075       <entry><type>text</type></entry>
4076       <entry></entry>
4077       <entry>
4078        This tells the function handler how to invoke the function.  It
4079        might be the actual source code of the function for interpreted
4080        languages, a link symbol, a file name, or just about anything
4081        else, depending on the implementation language/call convention.
4082       </entry>
4083      </row>
4084
4085      <row>
4086       <entry><structfield>probin</structfield></entry>
4087       <entry><type>text</type></entry>
4088       <entry></entry>
4089       <entry>
4090        Additional information about how to invoke the function.
4091        Again, the interpretation is language-specific.
4092       </entry>
4093      </row>
4094
4095      <row>
4096       <entry><structfield>proconfig</structfield></entry>
4097       <entry><type>text[]</type></entry>
4098       <entry></entry>
4099       <entry>Function's local settings for run-time configuration variables</entry>
4100      </row>
4101
4102      <row>
4103       <entry><structfield>proacl</structfield></entry>
4104       <entry><type>aclitem[]</type></entry>
4105       <entry></entry>
4106       <entry>
4107        Access privileges; see
4108        <xref linkend="sql-grant"> and
4109        <xref linkend="sql-revoke">
4110        for details
4111       </entry>
4112      </row>
4113     </tbody>
4114    </tgroup>
4115   </table>
4116
4117   <para>
4118    For compiled functions, both built-in and dynamically loaded,
4119    <structfield>prosrc</structfield> contains the function's C-language
4120    name (link symbol).  For all other currently-known language types,
4121    <structfield>prosrc</structfield> contains the function's source
4122    text.  <structfield>probin</structfield> is unused except for
4123    dynamically-loaded C functions, for which it gives the name of the
4124    shared library file containing the function.
4125   </para>
4126
4127  </sect1>
4128
4129  <sect1 id="catalog-pg-rewrite">
4130   <title><structname>pg_rewrite</structname></title>
4131
4132   <indexterm zone="catalog-pg-rewrite">
4133    <primary>pg_rewrite</primary>
4134   </indexterm>
4135
4136   <para>
4137    The catalog <structname>pg_rewrite</structname> stores rewrite rules for tables and views.
4138   </para>
4139
4140   <table>
4141    <title><structname>pg_rewrite</> Columns</title>
4142
4143    <tgroup cols="4">
4144     <thead>
4145      <row>
4146       <entry>Name</entry>
4147       <entry>Type</entry>
4148       <entry>References</entry>
4149       <entry>Description</entry>
4150      </row>
4151     </thead>
4152
4153     <tbody>
4154      <row>
4155       <entry><structfield>rulename</structfield></entry>
4156       <entry><type>name</type></entry>
4157       <entry></entry>
4158       <entry>Rule name</entry>
4159      </row>
4160
4161      <row>
4162       <entry><structfield>ev_class</structfield></entry>
4163       <entry><type>oid</type></entry>
4164       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
4165       <entry>The table this rule is for</entry>
4166      </row>
4167
4168      <row>
4169       <entry><structfield>ev_attr</structfield></entry>
4170       <entry><type>int2</type></entry>
4171       <entry></entry>
4172       <entry>The column this rule is for (currently, always zero to
4173       indicate the whole table)</entry>
4174      </row>
4175
4176      <row>
4177       <entry><structfield>ev_type</structfield></entry>
4178       <entry><type>char</type></entry>
4179       <entry></entry>
4180       <entry>
4181        Event type that the rule is for: 1 = <command>SELECT</>, 2 =
4182        <command>UPDATE</>, 3 = <command>INSERT</>, 4 =
4183        <command>DELETE</>
4184       </entry>
4185      </row>
4186
4187      <row>
4188       <entry><structfield>ev_enabled</structfield></entry>
4189       <entry><type>char</type></entry>
4190       <entry></entry>
4191       <entry>
4192        Controls in which <xref linkend="guc-session-replication-role"> modes
4193        the rule fires.
4194        <literal>O</> = rule fires in <quote>origin</> and <quote>local</> modes,
4195        <literal>D</> = rule is disabled,
4196        <literal>R</> = rule fires in <quote>replica</> mode,
4197        <literal>A</> = rule fires always.
4198       </entry>
4199      </row>
4200
4201      <row>
4202       <entry><structfield>is_instead</structfield></entry>
4203       <entry><type>bool</type></entry>
4204       <entry></entry>
4205       <entry>True if the rule is an <literal>INSTEAD</literal> rule</entry>
4206      </row>
4207
4208      <row>
4209       <entry><structfield>ev_qual</structfield></entry>
4210       <entry><type>pg_node_tree</type></entry>
4211       <entry></entry>
4212       <entry>
4213        Expression tree (in the form of a
4214        <function>nodeToString()</function> representation) for the
4215        rule's qualifying condition
4216       </entry>
4217      </row>
4218
4219      <row>
4220       <entry><structfield>ev_action</structfield></entry>
4221       <entry><type>pg_node_tree</type></entry>
4222       <entry></entry>
4223       <entry>
4224        Query tree (in the form of a
4225        <function>nodeToString()</function> representation) for the
4226        rule's action
4227       </entry>
4228      </row>
4229     </tbody>
4230    </tgroup>
4231   </table>
4232
4233   <note>
4234    <para>
4235     <literal>pg_class.relhasrules</literal>
4236     must be true if a table has any rules in this catalog.
4237    </para>
4238   </note>
4239
4240  </sect1>
4241
4242  <sect1 id="catalog-pg-db-role-setting">
4243   <title><structname>pg_db_role_setting</structname></title>
4244
4245   <indexterm zone="catalog-pg-db-role-setting">
4246    <primary>pg_db_role_setting</primary>
4247   </indexterm>
4248
4249   <para>
4250    The catalog <structname>pg_db_role_setting</structname> records the default
4251    values that have been set for run-time configuration variables,
4252    for each role and database combination.
4253   </para>
4254
4255   <para>
4256    Unlike most system catalogs, <structname>pg_db_role_setting</structname>
4257    is shared across all databases of a cluster: there is only one
4258    copy of <structname>pg_db_role_setting</structname> per cluster, not
4259    one per database.
4260   </para>
4261
4262   <table>
4263    <title><structname>pg_db_role_setting</> Columns</title>
4264
4265    <tgroup cols="4">
4266     <thead>
4267      <row>
4268       <entry>Name</entry>
4269       <entry>Type</entry>
4270       <entry>References</entry>
4271       <entry>Description</entry>
4272      </row>
4273     </thead>
4274
4275     <tbody>
4276      <row>
4277       <entry><structfield>setdatabase</structfield></entry>
4278       <entry><type>oid</type></entry>
4279       <entry><literal><link linkend="catalog-pg-database"><structname>pg_database</structname></link>.oid</literal></entry>
4280       <entry>The OID of the database the setting is applicable to, or zero if not database-specific</entry>
4281      </row>
4282
4283      <row>
4284       <entry><structfield>setrole</structfield></entry>
4285       <entry><type>oid</type></entry>
4286       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
4287       <entry>The OID of the role the setting is applicable to, or zero if not role-specific</entry>
4288      </row>
4289
4290      <row>
4291       <entry><structfield>setconfig</structfield></entry>
4292       <entry><type>text[]</type></entry>
4293       <entry></entry>
4294       <entry>Defaults for run-time configuration variables</entry>
4295      </row>
4296     </tbody>
4297    </tgroup>
4298   </table>
4299  </sect1>
4300
4301
4302  <sect1 id="catalog-pg-shdepend">
4303   <title><structname>pg_shdepend</structname></title>
4304
4305   <indexterm zone="catalog-pg-shdepend">
4306    <primary>pg_shdepend</primary>
4307   </indexterm>
4308
4309   <para>
4310    The catalog <structname>pg_shdepend</structname> records the
4311    dependency relationships between database objects and shared objects,
4312    such as roles.  This information allows
4313    <productname>PostgreSQL</productname> to ensure that those objects are
4314    unreferenced before attempting to delete them.
4315   </para>
4316
4317   <para>
4318    See also <link linkend="catalog-pg-depend"><structname>pg_depend</structname></link>,
4319    which performs a similar function for dependencies involving objects
4320    within a single database.
4321   </para>
4322
4323   <para>
4324    Unlike most system catalogs, <structname>pg_shdepend</structname>
4325    is shared across all databases of a cluster: there is only one
4326    copy of <structname>pg_shdepend</structname> per cluster, not
4327    one per database.
4328   </para>
4329
4330   <table>
4331    <title><structname>pg_shdepend</> Columns</title>
4332
4333    <tgroup cols="4">
4334     <thead>
4335      <row>
4336       <entry>Name</entry>
4337       <entry>Type</entry>
4338       <entry>References</entry>
4339       <entry>Description</entry>
4340      </row>
4341     </thead>
4342
4343     <tbody>
4344      <row>
4345       <entry><structfield>dbid</structfield></entry>
4346       <entry><type>oid</type></entry>
4347       <entry><literal><link linkend="catalog-pg-database"><structname>pg_database</structname></link>.oid</literal></entry>
4348       <entry>The OID of the database the dependent object is in,
4349        or zero for a shared object</entry>
4350      </row>
4351
4352      <row>
4353       <entry><structfield>classid</structfield></entry>
4354       <entry><type>oid</type></entry>
4355       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
4356       <entry>The OID of the system catalog the dependent object is in</entry>
4357      </row>
4358
4359      <row>
4360       <entry><structfield>objid</structfield></entry>
4361       <entry><type>oid</type></entry>
4362       <entry>any OID column</entry>
4363       <entry>The OID of the specific dependent object</entry>
4364      </row>
4365
4366      <row>
4367       <entry><structfield>objsubid</structfield></entry>
4368       <entry><type>int4</type></entry>
4369       <entry></entry>
4370       <entry>
4371        For a table column, this is the column number (the
4372        <structfield>objid</> and <structfield>classid</> refer to the
4373        table itself).  For all other object types, this column is zero.
4374       </entry>
4375      </row>
4376
4377      <row>
4378       <entry><structfield>refclassid</structfield></entry>
4379       <entry><type>oid</type></entry>
4380       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
4381       <entry>The OID of the system catalog the referenced object is in
4382        (must be a shared catalog)</entry>
4383      </row>
4384
4385      <row>
4386       <entry><structfield>refobjid</structfield></entry>
4387       <entry><type>oid</type></entry>
4388       <entry>any OID column</entry>
4389       <entry>The OID of the specific referenced object</entry>
4390      </row>
4391
4392      <row>
4393       <entry><structfield>deptype</structfield></entry>
4394       <entry><type>char</type></entry>
4395       <entry></entry>
4396       <entry>
4397        A code defining the specific semantics of this dependency relationship; see text
4398       </entry>
4399      </row>
4400
4401     </tbody>
4402    </tgroup>
4403   </table>
4404
4405   <para>
4406    In all cases, a <structname>pg_shdepend</structname> entry indicates that
4407    the referenced object cannot be dropped without also dropping the dependent
4408    object.  However, there are several subflavors identified by
4409    <structfield>deptype</>:
4410
4411    <variablelist>
4412     <varlistentry>
4413      <term><symbol>SHARED_DEPENDENCY_OWNER</> (<literal>o</>)</term>
4414      <listitem>
4415       <para>
4416        The referenced object (which must be a role) is the owner of the
4417        dependent object.
4418       </para>
4419      </listitem>
4420     </varlistentry>
4421
4422     <varlistentry>
4423      <term><symbol>SHARED_DEPENDENCY_ACL</> (<literal>a</>)</term>
4424      <listitem>
4425       <para>
4426        The referenced object (which must be a role) is mentioned in the
4427        ACL (access control list, i.e., privileges list) of the
4428        dependent object.  (A <symbol>SHARED_DEPENDENCY_ACL</> entry is
4429        not made for the owner of the object, since the owner will have
4430        a <symbol>SHARED_DEPENDENCY_OWNER</> entry anyway.)
4431       </para>
4432      </listitem>
4433     </varlistentry>
4434
4435     <varlistentry>
4436      <term><symbol>SHARED_DEPENDENCY_PIN</> (<literal>p</>)</term>
4437      <listitem>
4438       <para>
4439        There is no dependent object; this type of entry is a signal
4440        that the system itself depends on the referenced object, and so
4441        that object must never be deleted.  Entries of this type are
4442        created only by <command>initdb</command>.  The columns for the
4443        dependent object contain zeroes.
4444       </para>
4445      </listitem>
4446     </varlistentry>
4447    </variablelist>
4448
4449    Other dependency flavors might be needed in future.  Note in particular
4450    that the current definition only supports roles as referenced objects.
4451   </para>
4452
4453  </sect1>
4454
4455  <sect1 id="catalog-pg-shdescription">
4456   <title><structname>pg_shdescription</structname></title>
4457
4458   <indexterm zone="catalog-pg-shdescription">
4459    <primary>pg_shdescription</primary>
4460   </indexterm>
4461
4462   <para>
4463    The catalog <structname>pg_shdescription</structname> stores optional
4464    descriptions (comments) for shared database objects.  Descriptions can be
4465    manipulated with the <xref linkend="sql-comment"> command and viewed with
4466    <application>psql</application>'s <literal>\d</literal> commands.
4467   </para>
4468
4469   <para>
4470    See also <link linkend="catalog-pg-description"><structname>pg_description</structname></link>,
4471    which performs a similar function for descriptions involving objects
4472    within a single database.
4473   </para>
4474
4475   <para>
4476    Unlike most system catalogs, <structname>pg_shdescription</structname>
4477    is shared across all databases of a cluster: there is only one
4478    copy of <structname>pg_shdescription</structname> per cluster, not
4479    one per database.
4480   </para>
4481
4482   <table>
4483    <title><structname>pg_shdescription</> Columns</title>
4484
4485    <tgroup cols="4">
4486     <thead>
4487      <row>
4488       <entry>Name</entry>
4489       <entry>Type</entry>
4490       <entry>References</entry>
4491       <entry>Description</entry>
4492      </row>
4493     </thead>
4494
4495     <tbody>
4496      <row>
4497       <entry><structfield>objoid</structfield></entry>
4498       <entry><type>oid</type></entry>
4499       <entry>any OID column</entry>
4500       <entry>The OID of the object this description pertains to</entry>
4501      </row>
4502
4503      <row>
4504       <entry><structfield>classoid</structfield></entry>
4505       <entry><type>oid</type></entry>
4506       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
4507       <entry>The OID of the system catalog this object appears in</entry>
4508      </row>
4509
4510      <row>
4511       <entry><structfield>description</structfield></entry>
4512       <entry><type>text</type></entry>
4513       <entry></entry>
4514       <entry>Arbitrary text that serves as the description of this object</entry>
4515      </row>
4516     </tbody>
4517    </tgroup>
4518   </table>
4519
4520  </sect1>
4521
4522
4523  <sect1 id="catalog-pg-statistic">
4524   <title><structname>pg_statistic</structname></title>
4525
4526   <indexterm zone="catalog-pg-statistic">
4527    <primary>pg_statistic</primary>
4528   </indexterm>
4529
4530   <para>
4531    The catalog <structname>pg_statistic</structname> stores
4532    statistical data about the contents of the database.  Entries are
4533    created by <xref linkend="sql-analyze">
4534    and subsequently used by the query planner.  Note that all the
4535    statistical data is inherently approximate, even assuming that it
4536    is up-to-date.
4537   </para>
4538
4539   <para>
4540    Normally there is one entry, with <structfield>stainherit</> =
4541    <literal>false</>, for each table column that has been analyzed.
4542    If the table has inheritance children, a second entry with
4543    <structfield>stainherit</> = <literal>true</> is also created.  This row
4544    represents the column's statistics over the inheritance tree, i.e.,
4545    statistics for the data you'd see with
4546    <literal>SELECT <replaceable>column</> FROM <replaceable>table</>*</literal>,
4547    whereas the <structfield>stainherit</> = <literal>false</> row represents
4548    the results of
4549    <literal>SELECT <replaceable>column</> FROM ONLY <replaceable>table</></literal>.
4550   </para>
4551
4552   <para>
4553    <structname>pg_statistic</structname> also stores statistical data about
4554    the values of index expressions.  These are described as if they were
4555    actual data columns; in particular, <structfield>starelid</structfield>
4556    references the index.  No entry is made for an ordinary non-expression
4557    index column, however, since it would be redundant with the entry
4558    for the underlying table column.  Currently, entries for index expressions
4559    always have <structfield>stainherit</> = <literal>false</>.
4560   </para>
4561
4562   <para>
4563    Since different kinds of statistics might be appropriate for different
4564    kinds of data, <structname>pg_statistic</structname> is designed not
4565    to assume very much about what sort of statistics it stores.  Only
4566    extremely general statistics (such as nullness) are given dedicated
4567    columns in <structname>pg_statistic</structname>.  Everything else
4568    is stored in <quote>slots</quote>, which are groups of associated columns
4569    whose content is identified by a code number in one of the slot's columns.
4570    For more information see
4571    <filename>src/include/catalog/pg_statistic.h</filename>.
4572   </para>
4573
4574   <para>
4575    <structname>pg_statistic</structname> should not be readable by the
4576    public, since even statistical information about a table's contents
4577    might be considered sensitive.  (Example: minimum and maximum values
4578    of a salary column might be quite interesting.)
4579    <link linkend="view-pg-stats"><structname>pg_stats</structname></link>
4580    is a publicly readable view on
4581    <structname>pg_statistic</structname> that only exposes information
4582    about those tables that are readable by the current user.
4583   </para>
4584
4585   <table>
4586    <title><structname>pg_statistic</> Columns</title>
4587
4588    <tgroup cols="4">
4589     <thead>
4590      <row>
4591       <entry>Name</entry>
4592       <entry>Type</entry>
4593       <entry>References</entry>
4594       <entry>Description</entry>
4595      </row>
4596     </thead>
4597
4598     <tbody>
4599      <row>
4600       <entry><structfield>starelid</structfield></entry>
4601       <entry><type>oid</type></entry>
4602       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
4603       <entry>The table or index that the described column belongs to</entry>
4604      </row>
4605
4606      <row>
4607       <entry><structfield>staattnum</structfield></entry>
4608       <entry><type>int2</type></entry>
4609       <entry><literal><link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.attnum</literal></entry>
4610       <entry>The number of the described column</entry>
4611      </row>
4612
4613      <row>
4614       <entry><structfield>stainherit</structfield></entry>
4615       <entry><type>bool</type></entry>
4616       <entry></entry>
4617       <entry>If true, the stats include inheritance child columns, not just the
4618        values in the specified relation</entry>
4619      </row>
4620
4621      <row>
4622       <entry><structfield>stanullfrac</structfield></entry>
4623       <entry><type>float4</type></entry>
4624       <entry></entry>
4625       <entry>The fraction of the column's entries that are null</entry>
4626      </row>
4627
4628      <row>
4629       <entry><structfield>stawidth</structfield></entry>
4630       <entry><type>int4</type></entry>
4631       <entry></entry>
4632       <entry>The average stored width, in bytes, of nonnull entries</entry>
4633      </row>
4634
4635      <row>
4636       <entry><structfield>stadistinct</structfield></entry>
4637       <entry><type>float4</type></entry>
4638       <entry></entry>
4639       <entry>The number of distinct nonnull data values in the column.
4640       A value greater than zero is the actual number of distinct values.
4641       A value less than zero is the negative of a multiplier for the number
4642       of rows in the table; for example, a column in which values appear about
4643       twice on the average could be represented by
4644       <structfield>stadistinct</> = -0.5.
4645       A zero value means the number of distinct values is unknown.
4646       </entry>
4647      </row>
4648
4649      <row>
4650       <entry><structfield>stakind<replaceable>N</></structfield></entry>
4651       <entry><type>int2</type></entry>
4652       <entry></entry>
4653       <entry>
4654        A code number indicating the kind of statistics stored in the
4655        <replaceable>N</>th <quote>slot</quote> of the
4656        <structname>pg_statistic</structname> row.
4657       </entry>
4658      </row>
4659
4660      <row>
4661       <entry><structfield>staop<replaceable>N</></structfield></entry>
4662       <entry><type>oid</type></entry>
4663       <entry><literal><link linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.oid</literal></entry>
4664       <entry>
4665        An operator used to derive the statistics stored in the
4666        <replaceable>N</>th <quote>slot</quote>.  For example, a
4667        histogram slot would show the <literal>&lt;</literal> operator
4668        that defines the sort order of the data.
4669       </entry>
4670      </row>
4671
4672      <row>
4673       <entry><structfield>stanumbers<replaceable>N</></structfield></entry>
4674       <entry><type>float4[]</type></entry>
4675       <entry></entry>
4676       <entry>
4677        Numerical statistics of the appropriate kind for the
4678        <replaceable>N</>th <quote>slot</quote>, or null if the slot
4679        kind does not involve numerical values
4680       </entry>
4681      </row>
4682
4683      <row>
4684       <entry><structfield>stavalues<replaceable>N</></structfield></entry>
4685       <entry><type>anyarray</type></entry>
4686       <entry></entry>
4687       <entry>
4688        Column data values of the appropriate kind for the
4689        <replaceable>N</>th <quote>slot</quote>, or null if the slot
4690        kind does not store any data values.  Each array's element
4691        values are actually of the specific column's data type, so there
4692        is no way to define these columns' type more specifically than
4693        <type>anyarray</>.
4694       </entry>
4695      </row>
4696     </tbody>
4697    </tgroup>
4698   </table>
4699
4700  </sect1>
4701
4702
4703  <sect1 id="catalog-pg-tablespace">
4704   <title><structname>pg_tablespace</structname></title>
4705
4706   <indexterm zone="catalog-pg-tablespace">
4707    <primary>pg_tablespace</primary>
4708   </indexterm>
4709
4710   <para>
4711    The catalog <structname>pg_tablespace</structname> stores information
4712    about the available tablespaces.  Tables can be placed in particular
4713    tablespaces to aid administration of disk layout.
4714   </para>
4715
4716   <para>
4717    Unlike most system catalogs, <structname>pg_tablespace</structname>
4718    is shared across all databases of a cluster: there is only one
4719    copy of <structname>pg_tablespace</structname> per cluster, not
4720    one per database.
4721   </para>
4722
4723   <table>
4724    <title><structname>pg_tablespace</> Columns</title>
4725
4726    <tgroup cols="4">
4727     <thead>
4728      <row>
4729       <entry>Name</entry>
4730       <entry>Type</entry>
4731       <entry>References</entry>
4732       <entry>Description</entry>
4733      </row>
4734     </thead>
4735
4736     <tbody>
4737      <row>
4738       <entry><structfield>spcname</structfield></entry>
4739       <entry><type>name</type></entry>
4740       <entry></entry>
4741       <entry>Tablespace name</entry>
4742      </row>
4743
4744      <row>
4745       <entry><structfield>spcowner</structfield></entry>
4746       <entry><type>oid</type></entry>
4747       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
4748       <entry>Owner of the tablespace, usually the user who created it</entry>
4749      </row>
4750
4751      <row>
4752       <entry><structfield>spclocation</structfield></entry>
4753       <entry><type>text</type></entry>
4754       <entry></entry>
4755       <entry>Location (directory path) of the tablespace</entry>
4756      </row>
4757
4758      <row>
4759       <entry><structfield>spcacl</structfield></entry>
4760       <entry><type>aclitem[]</type></entry>
4761       <entry></entry>
4762       <entry>
4763        Access privileges; see
4764        <xref linkend="sql-grant"> and
4765        <xref linkend="sql-revoke">
4766        for details
4767       </entry>
4768      </row>
4769
4770      <row>
4771       <entry><structfield>spcoptions</structfield></entry>
4772       <entry><type>text[]</type></entry>
4773       <entry></entry>
4774       <entry>
4775        Tablespace-level options, as <quote>keyword=value</> strings
4776       </entry>
4777      </row>
4778     </tbody>
4779    </tgroup>
4780   </table>
4781  </sect1>
4782
4783
4784  <sect1 id="catalog-pg-trigger">
4785   <title><structname>pg_trigger</structname></title>
4786
4787   <indexterm zone="catalog-pg-trigger">
4788    <primary>pg_trigger</primary>
4789   </indexterm>
4790
4791   <para>
4792    The catalog <structname>pg_trigger</structname> stores triggers on tables.
4793    See <xref linkend="sql-createtrigger">
4794    for more information.
4795   </para>
4796
4797   <table>
4798    <title><structname>pg_trigger</> Columns</title>
4799
4800    <tgroup cols="4">
4801     <thead>
4802      <row>
4803       <entry>Name</entry>
4804       <entry>Type</entry>
4805       <entry>References</entry>
4806       <entry>Description</entry>
4807      </row>
4808     </thead>
4809
4810     <tbody>
4811      <row>
4812       <entry><structfield>tgrelid</structfield></entry>
4813       <entry><type>oid</type></entry>
4814       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
4815       <entry>The table this trigger is on</entry>
4816      </row>
4817
4818      <row>
4819       <entry><structfield>tgname</structfield></entry>
4820       <entry><type>name</type></entry>
4821       <entry></entry>
4822       <entry>Trigger name (must be unique among triggers of same table)</entry>
4823      </row>
4824
4825      <row>
4826       <entry><structfield>tgfoid</structfield></entry>
4827       <entry><type>oid</type></entry>
4828       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
4829       <entry>The function to be called</entry>
4830      </row>
4831
4832      <row>
4833       <entry><structfield>tgtype</structfield></entry>
4834       <entry><type>int2</type></entry>
4835       <entry></entry>
4836       <entry>Bit mask identifying trigger conditions</entry>
4837      </row>
4838
4839      <row>
4840       <entry><structfield>tgenabled</structfield></entry>
4841       <entry><type>char</type></entry>
4842       <entry></entry>
4843       <entry>
4844        Controls in which <xref linkend="guc-session-replication-role"> modes
4845        the trigger fires.
4846        <literal>O</> = trigger fires in <quote>origin</> and <quote>local</> modes,
4847        <literal>D</> = trigger is disabled,
4848        <literal>R</> = trigger fires in <quote>replica</> mode,
4849        <literal>A</> = trigger fires always.
4850       </entry>
4851      </row>
4852
4853      <row>
4854       <entry><structfield>tgisinternal</structfield></entry>
4855       <entry><type>bool</type></entry>
4856       <entry></entry>
4857       <entry>True if trigger is internally generated (usually, to enforce
4858        the constraint identified by <structfield>tgconstraint</>)</entry>
4859      </row>
4860
4861      <row>
4862       <entry><structfield>tgconstrrelid</structfield></entry>
4863       <entry><type>oid</type></entry>
4864       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
4865       <entry>The table referenced by a referential integrity constraint</entry>
4866      </row>
4867
4868      <row>
4869       <entry><structfield>tgconstrindid</structfield></entry>
4870       <entry><type>oid</type></entry>
4871       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
4872       <entry>The index supporting a unique, primary key, or referential integrity constraint</entry>
4873      </row>
4874
4875      <row>
4876       <entry><structfield>tgconstraint</structfield></entry>
4877       <entry><type>oid</type></entry>
4878       <entry><literal><link linkend="catalog-pg-constraint"><structname>pg_constraint</structname></link>.oid</literal></entry>
4879       <entry>The <structname>pg_constraint</> entry associated with the trigger, if any</entry>
4880      </row>
4881
4882      <row>
4883       <entry><structfield>tgdeferrable</structfield></entry>
4884       <entry><type>bool</type></entry>
4885       <entry></entry>
4886       <entry>True if constraint trigger is deferrable</entry>
4887      </row>
4888
4889      <row>
4890       <entry><structfield>tginitdeferred</structfield></entry>
4891       <entry><type>bool</type></entry>
4892       <entry></entry>
4893       <entry>True if constraint trigger is initially deferred</entry>
4894      </row>
4895
4896      <row>
4897       <entry><structfield>tgnargs</structfield></entry>
4898       <entry><type>int2</type></entry>
4899       <entry></entry>
4900       <entry>Number of argument strings passed to trigger function</entry>
4901      </row>
4902
4903      <row>
4904       <entry><structfield>tgattr</structfield></entry>
4905       <entry><type>int2vector</type></entry>
4906       <entry><literal><link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.attnum</literal></entry>
4907       <entry>Column numbers, if trigger is column-specific; otherwise an
4908        empty array</entry>
4909      </row>
4910
4911      <row>
4912       <entry><structfield>tgargs</structfield></entry>
4913       <entry><type>bytea</type></entry>
4914       <entry></entry>
4915       <entry>Argument strings to pass to trigger, each NULL-terminated</entry>
4916      </row>
4917
4918      <row>
4919       <entry><structfield>tgqual</structfield></entry>
4920       <entry><type>pg_node_tree</type></entry>
4921       <entry></entry>
4922       <entry>Expression tree (in <function>nodeToString()</function>
4923        representation) for the trigger's <literal>WHEN</> condition, or null
4924        if none</entry>
4925      </row>
4926     </tbody>
4927    </tgroup>
4928   </table>
4929
4930   <para>
4931    Currently, column-specific triggering is supported only for
4932    <literal>UPDATE</> events, and so <structfield>tgattr</> is relevant
4933    only for that event type.  <structfield>tgtype</structfield> might
4934    contain bits for other event types as well, but those are presumed
4935    to be table-wide regardless of what is in <structfield>tgattr</>.
4936   </para>
4937
4938   <note>
4939    <para>
4940     When <structfield>tgconstraint</> is nonzero,
4941     <structfield>tgconstrrelid</>, <structfield>tgconstrindid</>,
4942     <structfield>tgdeferrable</>, and <structfield>tginitdeferred</> are
4943     largely redundant with the referenced <structname>pg_constraint</> entry.
4944     However, it is possible for a non-deferrable trigger to be associated
4945     with a deferrable constraint: foreign key constraints can have some
4946     deferrable and some non-deferrable triggers.
4947    </para>
4948   </note>
4949
4950   <note>
4951    <para>
4952     <literal>pg_class.relhastriggers</literal>
4953     must be true if a table has any triggers in this catalog.
4954    </para>
4955   </note>
4956
4957  </sect1>
4958
4959
4960  <sect1 id="catalog-pg-ts-config">
4961   <title><structname>pg_ts_config</structname></title>
4962
4963   <indexterm zone="catalog-pg-ts-config">
4964    <primary>pg_ts_config</primary>
4965   </indexterm>
4966
4967   <para>
4968    The <structname>pg_ts_config</structname> catalog contains entries
4969    representing text search configurations.  A configuration specifies
4970    a particular text search parser and a list of dictionaries to use
4971    for each of the parser's output token types.  The parser is shown
4972    in the <structname>pg_ts_config</structname> entry, but the
4973    token-to-dictionary mapping is defined by subsidiary entries in <link
4974    linkend="catalog-pg-ts-config-map"><structname>pg_ts_config_map</structname></link>.
4975   </para>
4976
4977   <para>
4978    <productname>PostgreSQL</productname>'s text search features are
4979    described at length in <xref linkend="textsearch">.
4980   </para>
4981
4982   <table>
4983    <title><structname>pg_ts_config</> Columns</title>
4984
4985    <tgroup cols="4">
4986     <thead>
4987      <row>
4988       <entry>Name</entry>
4989       <entry>Type</entry>
4990       <entry>References</entry>
4991       <entry>Description</entry>
4992      </row>
4993     </thead>
4994
4995     <tbody>
4996      <row>
4997       <entry><structfield>cfgname</structfield></entry>
4998       <entry><type>name</type></entry>
4999       <entry></entry>
5000       <entry>Text search configuration name</entry>
5001      </row>
5002
5003      <row>
5004       <entry><structfield>cfgnamespace</structfield></entry>
5005       <entry><type>oid</type></entry>
5006       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>
5007       <entry>
5008        The OID of the namespace that contains this configuration
5009       </entry>
5010      </row>
5011
5012      <row>
5013       <entry><structfield>cfgowner</structfield></entry>
5014       <entry><type>oid</type></entry>
5015       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
5016       <entry>Owner of the configuration</entry>
5017      </row>
5018
5019      <row>
5020       <entry><structfield>cfgparser</structfield></entry>
5021       <entry><type>oid</type></entry>
5022       <entry><literal><link linkend="catalog-pg-ts-parser"><structname>pg_ts_parser</structname></link>.oid</literal></entry>
5023       <entry>The OID of the text search parser for this configuration</entry>
5024      </row>
5025     </tbody>
5026    </tgroup>
5027   </table>
5028  </sect1>
5029
5030
5031  <sect1 id="catalog-pg-ts-config-map">
5032   <title><structname>pg_ts_config_map</structname></title>
5033
5034   <indexterm zone="catalog-pg-ts-config-map">
5035    <primary>pg_ts_config_map</primary>
5036   </indexterm>
5037
5038   <para>
5039    The <structname>pg_ts_config_map</structname> catalog contains entries
5040    showing which text search dictionaries should be consulted, and in
5041    what order, for each output token type of each text search configuration's
5042    parser.
5043   </para>
5044
5045   <para>
5046    <productname>PostgreSQL</productname>'s text search features are
5047    described at length in <xref linkend="textsearch">.
5048   </para>
5049
5050   <table>
5051    <title><structname>pg_ts_config_map</> Columns</title>
5052
5053    <tgroup cols="4">
5054     <thead>
5055      <row>
5056       <entry>Name</entry>
5057       <entry>Type</entry>
5058       <entry>References</entry>
5059       <entry>Description</entry>
5060      </row>
5061     </thead>
5062
5063     <tbody>
5064      <row>
5065       <entry><structfield>mapcfg</structfield></entry>
5066       <entry><type>oid</type></entry>
5067       <entry><literal><link linkend="catalog-pg-ts-config"><structname>pg_ts_config</structname></link>.oid</literal></entry>
5068       <entry>The OID of the <structname>pg_ts_config</> entry owning this map entry</entry>
5069      </row>
5070
5071      <row>
5072       <entry><structfield>maptokentype</structfield></entry>
5073       <entry><type>integer</type></entry>
5074       <entry></entry>
5075       <entry>A token type emitted by the configuration's parser</entry>
5076      </row>
5077
5078      <row>
5079       <entry><structfield>mapseqno</structfield></entry>
5080       <entry><type>integer</type></entry>
5081       <entry></entry>
5082       <entry>Order in which to consult this entry (lower
5083        <structfield>mapseqno</>s first)</entry>
5084      </row>
5085
5086      <row>
5087       <entry><structfield>mapdict</structfield></entry>
5088       <entry><type>oid</type></entry>
5089       <entry><literal><link linkend="catalog-pg-ts-dict"><structname>pg_ts_dict</structname></link>.oid</literal></entry>
5090       <entry>The OID of the text search dictionary to consult</entry>
5091      </row>
5092     </tbody>
5093    </tgroup>
5094   </table>
5095  </sect1>
5096
5097
5098  <sect1 id="catalog-pg-ts-dict">
5099   <title><structname>pg_ts_dict</structname></title>
5100
5101   <indexterm zone="catalog-pg-ts-dict">
5102    <primary>pg_ts_dict</primary>
5103   </indexterm>
5104
5105   <para>
5106    The <structname>pg_ts_dict</structname> catalog contains entries
5107    defining text search dictionaries.  A dictionary depends on a text
5108    search template, which specifies all the implementation functions
5109    needed; the dictionary itself provides values for the user-settable
5110    parameters supported by the template.  This division of labor allows
5111    dictionaries to be created by unprivileged users.  The parameters
5112    are specified by a text string <structfield>dictinitoption</>,
5113    whose format and meaning vary depending on the template.
5114   </para>
5115
5116   <para>
5117    <productname>PostgreSQL</productname>'s text search features are
5118    described at length in <xref linkend="textsearch">.
5119   </para>
5120
5121   <table>
5122    <title><structname>pg_ts_dict</> Columns</title>
5123
5124    <tgroup cols="4">
5125     <thead>
5126      <row>
5127       <entry>Name</entry>
5128       <entry>Type</entry>
5129       <entry>References</entry>
5130       <entry>Description</entry>
5131      </row>
5132     </thead>
5133
5134     <tbody>
5135      <row>
5136       <entry><structfield>dictname</structfield></entry>
5137       <entry><type>name</type></entry>
5138       <entry></entry>
5139       <entry>Text search dictionary name</entry>
5140      </row>
5141
5142      <row>
5143       <entry><structfield>dictnamespace</structfield></entry>
5144       <entry><type>oid</type></entry>
5145       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>
5146       <entry>
5147        The OID of the namespace that contains this dictionary
5148       </entry>
5149      </row>
5150
5151      <row>
5152       <entry><structfield>dictowner</structfield></entry>
5153       <entry><type>oid</type></entry>
5154       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
5155       <entry>Owner of the dictionary</entry>
5156      </row>
5157
5158      <row>
5159       <entry><structfield>dicttemplate</structfield></entry>
5160       <entry><type>oid</type></entry>
5161       <entry><literal><link linkend="catalog-pg-ts-template"><structname>pg_ts_template</structname></link>.oid</literal></entry>
5162       <entry>The OID of the text search template for this dictionary</entry>
5163      </row>
5164
5165      <row>
5166       <entry><structfield>dictinitoption</structfield></entry>
5167       <entry><type>text</type></entry>
5168       <entry></entry>
5169       <entry>Initialization option string for the template</entry>
5170      </row>
5171     </tbody>
5172    </tgroup>
5173   </table>
5174  </sect1>
5175
5176
5177  <sect1 id="catalog-pg-ts-parser">
5178   <title><structname>pg_ts_parser</structname></title>
5179
5180   <indexterm zone="catalog-pg-ts-parser">
5181    <primary>pg_ts_parser</primary>
5182   </indexterm>
5183
5184   <para>
5185    The <structname>pg_ts_parser</structname> catalog contains entries
5186    defining text search parsers.  A parser is responsible for splitting
5187    input text into lexemes and assigning a token type to each lexeme.
5188    Since a parser must be implemented by C-language-level functions,
5189    creation of new parsers is restricted to database superusers.
5190   </para>
5191
5192   <para>
5193    <productname>PostgreSQL</productname>'s text search features are
5194    described at length in <xref linkend="textsearch">.
5195   </para>
5196
5197   <table>
5198    <title><structname>pg_ts_parser</> Columns</title>
5199
5200    <tgroup cols="4">
5201     <thead>
5202      <row>
5203       <entry>Name</entry>
5204       <entry>Type</entry>
5205       <entry>References</entry>
5206       <entry>Description</entry>
5207      </row>
5208     </thead>
5209
5210     <tbody>
5211      <row>
5212       <entry><structfield>prsname</structfield></entry>
5213       <entry><type>name</type></entry>
5214       <entry></entry>
5215       <entry>Text search parser name</entry>
5216      </row>
5217
5218      <row>
5219       <entry><structfield>prsnamespace</structfield></entry>
5220       <entry><type>oid</type></entry>
5221       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>
5222       <entry>
5223        The OID of the namespace that contains this parser
5224       </entry>
5225      </row>
5226
5227      <row>
5228       <entry><structfield>prsstart</structfield></entry>
5229       <entry><type>regproc</type></entry>
5230       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
5231       <entry>OID of the parser's startup function</entry>
5232      </row>
5233
5234      <row>
5235       <entry><structfield>prstoken</structfield></entry>
5236       <entry><type>regproc</type></entry>
5237       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
5238       <entry>OID of the parser's next-token function</entry>
5239      </row>
5240
5241      <row>
5242       <entry><structfield>prsend</structfield></entry>
5243       <entry><type>regproc</type></entry>
5244       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
5245       <entry>OID of the parser's shutdown function</entry>
5246      </row>
5247
5248      <row>
5249       <entry><structfield>prsheadline</structfield></entry>
5250       <entry><type>regproc</type></entry>
5251       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
5252       <entry>OID of the parser's headline function</entry>
5253      </row>
5254
5255      <row>
5256       <entry><structfield>prslextype</structfield></entry>
5257       <entry><type>regproc</type></entry>
5258       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
5259       <entry>OID of the parser's lextype function</entry>
5260      </row>
5261     </tbody>
5262    </tgroup>
5263   </table>
5264  </sect1>
5265
5266
5267  <sect1 id="catalog-pg-ts-template">
5268   <title><structname>pg_ts_template</structname></title>
5269
5270   <indexterm zone="catalog-pg-ts-template">
5271    <primary>pg_ts_template</primary>
5272   </indexterm>
5273
5274   <para>
5275    The <structname>pg_ts_template</structname> catalog contains entries
5276    defining text search templates.  A template is the implementation
5277    skeleton for a class of text search dictionaries.
5278    Since a template must be implemented by C-language-level functions,
5279    creation of new templates is restricted to database superusers.
5280   </para>
5281
5282   <para>
5283    <productname>PostgreSQL</productname>'s text search features are
5284    described at length in <xref linkend="textsearch">.
5285   </para>
5286
5287   <table>
5288    <title><structname>pg_ts_template</> Columns</title>
5289
5290    <tgroup cols="4">
5291     <thead>
5292      <row>
5293       <entry>Name</entry>
5294       <entry>Type</entry>
5295       <entry>References</entry>
5296       <entry>Description</entry>
5297      </row>
5298     </thead>
5299
5300     <tbody>
5301      <row>
5302       <entry><structfield>tmplname</structfield></entry>
5303       <entry><type>name</type></entry>
5304       <entry></entry>
5305       <entry>Text search template name</entry>
5306      </row>
5307
5308      <row>
5309       <entry><structfield>tmplnamespace</structfield></entry>
5310       <entry><type>oid</type></entry>
5311       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>
5312       <entry>
5313        The OID of the namespace that contains this template
5314       </entry>
5315      </row>
5316
5317      <row>
5318       <entry><structfield>tmplinit</structfield></entry>
5319       <entry><type>regproc</type></entry>
5320       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
5321       <entry>OID of the template's initialization function</entry>
5322      </row>
5323
5324      <row>
5325       <entry><structfield>tmpllexize</structfield></entry>
5326       <entry><type>regproc</type></entry>
5327       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
5328       <entry>OID of the template's lexize function</entry>
5329      </row>
5330     </tbody>
5331    </tgroup>
5332   </table>
5333  </sect1>
5334
5335
5336  <sect1 id="catalog-pg-type">
5337   <title><structname>pg_type</structname></title>
5338
5339   <indexterm zone="catalog-pg-type">
5340    <primary>pg_type</primary>
5341   </indexterm>
5342
5343   <para>
5344    The catalog <structname>pg_type</structname> stores information about data
5345    types.  Base types and enum types (scalar types) are created with
5346    <xref linkend="sql-createtype">, and
5347    domains with
5348    <xref linkend="sql-createdomain">.
5349    A composite type is automatically created for each table in the database, to
5350    represent the row structure of the table.  It is also possible to create
5351    composite types with <command>CREATE TYPE AS</command>.
5352   </para>
5353
5354   <table>
5355    <title><structname>pg_type</> Columns</title>
5356
5357    <tgroup cols="4">
5358     <thead>
5359      <row>
5360       <entry>Name</entry>
5361       <entry>Type</entry>
5362       <entry>References</entry>
5363       <entry>Description</entry>
5364      </row>
5365     </thead>
5366
5367     <tbody>
5368      <row>
5369       <entry><structfield>typname</structfield></entry>
5370       <entry><type>name</type></entry>
5371       <entry></entry>
5372       <entry>Data type name</entry>
5373      </row>
5374
5375      <row>
5376       <entry><structfield>typnamespace</structfield></entry>
5377       <entry><type>oid</type></entry>
5378       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>
5379       <entry>
5380        The OID of the namespace that contains this type
5381       </entry>
5382      </row>
5383
5384      <row>
5385       <entry><structfield>typowner</structfield></entry>
5386       <entry><type>oid</type></entry>
5387       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
5388       <entry>Owner of the type</entry>
5389      </row>
5390
5391      <row>
5392       <entry><structfield>typlen</structfield></entry>
5393       <entry><type>int2</type></entry>
5394       <entry></entry>
5395       <entry>
5396        For a fixed-size type, <structfield>typlen</structfield> is the number
5397        of bytes in the internal representation of the type.  But for a
5398        variable-length type, <structfield>typlen</structfield> is negative.
5399        -1 indicates a <quote>varlena</> type (one that has a length word),
5400        -2 indicates a null-terminated C string.
5401       </entry>
5402      </row>
5403
5404      <row>
5405       <entry><structfield>typbyval</structfield></entry>
5406       <entry><type>bool</type></entry>
5407       <entry></entry>
5408       <entry>
5409        <structfield>typbyval</structfield> determines whether internal
5410        routines pass a value of this type by value or by reference.
5411        <structfield>typbyval</structfield> had better be false if
5412        <structfield>typlen</structfield> is not 1, 2, or 4 (or 8 on machines
5413        where Datum is 8 bytes).
5414        Variable-length types are always passed by reference. Note that
5415        <structfield>typbyval</structfield> can be false even if the
5416        length would allow pass-by-value.
5417       </entry>
5418      </row>
5419
5420      <row>
5421       <entry><structfield>typtype</structfield></entry>
5422       <entry><type>char</type></entry>
5423       <entry></entry>
5424       <entry>
5425        <structfield>typtype</structfield> is
5426        <literal>b</literal> for a base type,
5427        <literal>c</literal> for a composite type (e.g., a table's row type),
5428        <literal>d</literal> for a domain,
5429        <literal>e</literal> for an enum type,
5430        or <literal>p</literal> for a pseudo-type.
5431        See also <structfield>typrelid</structfield> and
5432        <structfield>typbasetype</structfield>.
5433       </entry>
5434      </row>
5435
5436      <row>
5437       <entry><structfield>typcategory</structfield></entry>
5438       <entry><type>char</type></entry>
5439       <entry></entry>
5440       <entry>
5441        <structfield>typcategory</structfield> is an arbitrary classification
5442        of data types that is used by the parser to determine which implicit
5443        casts should be <quote>preferred</>.
5444        See <xref linkend="catalog-typcategory-table">.
5445       </entry>
5446      </row>
5447
5448      <row>
5449       <entry><structfield>typispreferred</structfield></entry>
5450       <entry><type>bool</type></entry>
5451       <entry></entry>
5452       <entry>
5453        True if the type is a preferred cast target within its
5454        <structfield>typcategory</structfield>
5455       </entry>
5456      </row>
5457
5458      <row>
5459       <entry><structfield>typisdefined</structfield></entry>
5460       <entry><type>bool</type></entry>
5461       <entry></entry>
5462       <entry>
5463        True if the type is defined, false if this is a placeholder
5464        entry for a not-yet-defined type.  When
5465        <structfield>typisdefined</structfield> is false, nothing
5466        except the type name, namespace, and OID can be relied on.
5467       </entry>
5468      </row>
5469
5470      <row>
5471       <entry><structfield>typdelim</structfield></entry>
5472       <entry><type>char</type></entry>
5473       <entry></entry>
5474       <entry>
5475        Character that separates two values of this type when parsing
5476        array input.  Note that the delimiter is associated with the array
5477        element data type, not the array data type.
5478       </entry>
5479      </row>
5480
5481      <row>
5482       <entry><structfield>typrelid</structfield></entry>
5483       <entry><type>oid</type></entry>
5484       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
5485       <entry>
5486        If this is a composite type (see
5487        <structfield>typtype</structfield>), then this column points to
5488        the <structname>pg_class</structname> entry that defines the
5489        corresponding table.  (For a free-standing composite type, the
5490        <structname>pg_class</structname> entry doesn't really represent
5491        a table, but it is needed anyway for the type's
5492        <structname>pg_attribute</structname> entries to link to.)
5493        Zero for non-composite types.
5494       </entry>
5495      </row>
5496
5497      <row>
5498       <entry><structfield>typelem</structfield></entry>
5499       <entry><type>oid</type></entry>
5500       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
5501       <entry>
5502        If <structfield>typelem</structfield> is not 0 then it
5503        identifies another row in <structname>pg_type</structname>.
5504        The current type can then be subscripted like an array yielding
5505        values of type <structfield>typelem</structfield>.  A
5506        <quote>true</quote> array type is variable length
5507        (<structfield>typlen</structfield> = -1),
5508        but some fixed-length (<structfield>typlen</structfield> &gt; 0) types
5509        also have nonzero <structfield>typelem</structfield>, for example
5510        <type>name</type> and <type>point</type>.
5511        If a fixed-length type has a <structfield>typelem</structfield> then
5512        its internal representation must be some number of values of the
5513        <structfield>typelem</structfield> data type with no other data.
5514        Variable-length array types have a header defined by the array
5515        subroutines.
5516       </entry>
5517      </row>
5518
5519      <row>
5520       <entry><structfield>typarray</structfield></entry>
5521       <entry><type>oid</type></entry>
5522       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
5523       <entry>
5524        If <structfield>typarray</structfield> is not 0 then it
5525        identifies another row in <structname>pg_type</structname>, which
5526        is the <quote>true</quote> array type having this type as element
5527       </entry>
5528      </row>
5529
5530      <row>
5531       <entry><structfield>typinput</structfield></entry>
5532       <entry><type>regproc</type></entry>
5533       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
5534       <entry>Input conversion function (text format)</entry>
5535      </row>
5536
5537      <row>
5538       <entry><structfield>typoutput</structfield></entry>
5539       <entry><type>regproc</type></entry>
5540       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
5541       <entry>Output conversion function (text format)</entry>
5542      </row>
5543
5544      <row>
5545       <entry><structfield>typreceive</structfield></entry>
5546       <entry><type>regproc</type></entry>
5547       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
5548       <entry>Input conversion function (binary format), or 0 if none</entry>
5549      </row>
5550
5551      <row>
5552       <entry><structfield>typsend</structfield></entry>
5553       <entry><type>regproc</type></entry>
5554       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
5555       <entry>Output conversion function (binary format), or 0 if none</entry>
5556      </row>
5557
5558      <row>
5559       <entry><structfield>typmodin</structfield></entry>
5560       <entry><type>regproc</type></entry>
5561       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
5562       <entry>Type modifier input function, or 0 if type does not support modifiers</entry>
5563      </row>
5564
5565      <row>
5566       <entry><structfield>typmodout</structfield></entry>
5567       <entry><type>regproc</type></entry>
5568       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
5569       <entry>Type modifier output function, or 0 to use the standard format</entry>
5570      </row>
5571
5572      <row>
5573       <entry><structfield>typanalyze</structfield></entry>
5574       <entry><type>regproc</type></entry>
5575       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
5576       <entry>Custom <command>ANALYZE</command> function, or 0 to use the standard function</entry>
5577      </row>
5578
5579      <row>
5580       <entry><structfield>typalign</structfield></entry>
5581       <entry><type>char</type></entry>
5582       <entry></entry>
5583       <entry><para>
5584
5585        <structfield>typalign</structfield> is the alignment required
5586        when storing a value of this type.  It applies to storage on
5587        disk as well as most representations of the value inside
5588        <productname>PostgreSQL</>.
5589        When multiple values are stored consecutively, such
5590        as in the representation of a complete row on disk, padding is
5591        inserted before a datum of this type so that it begins on the
5592        specified boundary.  The alignment reference is the beginning
5593        of the first datum in the sequence.
5594       </para>
5595
5596       <para>
5597        Possible values are:
5598        <itemizedlist>
5599         <listitem>
5600          <para><literal>c</> = <type>char</type> alignment, i.e., no alignment needed.</para>
5601         </listitem>
5602         <listitem>
5603          <para><literal>s</> = <type>short</type> alignment (2 bytes on most machines).</para>
5604         </listitem>
5605         <listitem>
5606          <para><literal>i</> = <type>int</type> alignment (4 bytes on most machines).</para>
5607         </listitem>
5608         <listitem>
5609          <para><literal>d</> = <type>double</type> alignment (8 bytes on many machines, but by no means all).</para>
5610         </listitem>
5611        </itemizedlist>
5612       </para><note>
5613        <para>
5614         For types used in system tables, it is critical that the size
5615         and alignment defined in <structname>pg_type</structname>
5616         agree with the way that the compiler will lay out the column in
5617         a structure representing a table row.
5618        </para>
5619       </note></entry>
5620      </row>
5621
5622      <row>
5623       <entry><structfield>typstorage</structfield></entry>
5624       <entry><type>char</type></entry>
5625       <entry></entry>
5626       <entry><para>
5627        <structfield>typstorage</structfield> tells for varlena
5628        types (those with <structfield>typlen</structfield> = -1) if
5629        the type is prepared for toasting and what the default strategy
5630        for attributes of this type should be.
5631        Possible values are
5632        <itemizedlist>
5633         <listitem>
5634          <para><literal>p</>: Value must always be stored plain.</para>
5635         </listitem>
5636         <listitem>
5637          <para>
5638           <literal>e</>: Value can be stored in a <quote>secondary</quote>
5639           relation (if relation has one, see
5640           <literal>pg_class.reltoastrelid</literal>).
5641          </para>
5642         </listitem>
5643         <listitem>
5644          <para><literal>m</>: Value can be stored compressed inline.</para>
5645         </listitem>
5646         <listitem>
5647          <para><literal>x</>: Value can be stored compressed inline or stored in <quote>secondary</quote> storage.</para>
5648         </listitem>
5649        </itemizedlist>
5650        Note that <literal>m</> columns can also be moved out to secondary
5651        storage, but only as a last resort (<literal>e</> and <literal>x</> columns are
5652        moved first).
5653       </para></entry>
5654      </row>
5655
5656      <row>
5657       <entry><structfield>typnotnull</structfield></entry>
5658       <entry><type>bool</type></entry>
5659       <entry></entry>
5660       <entry><para>
5661        <structfield>typnotnull</structfield> represents a not-null
5662        constraint on a type.  Used for domains only.
5663       </para></entry>
5664      </row>
5665
5666      <row>
5667       <entry><structfield>typbasetype</structfield></entry>
5668       <entry><type>oid</type></entry>
5669       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
5670       <entry><para>
5671        If this is a domain (see <structfield>typtype</structfield>), then
5672        <structfield>typbasetype</structfield> identifies the type that this
5673        one is based on.  Zero if this type is not a domain.
5674       </para></entry>
5675      </row>
5676
5677      <row>
5678       <entry><structfield>typtypmod</structfield></entry>
5679       <entry><type>int4</type></entry>
5680       <entry></entry>
5681       <entry><para>
5682        Domains use <structfield>typtypmod</structfield> to record the <literal>typmod</>
5683        to be applied to their base type (-1 if base type does not use a
5684        <literal>typmod</>).  -1 if this type is not a domain.
5685       </para></entry>
5686      </row>
5687
5688      <row>
5689       <entry><structfield>typndims</structfield></entry>
5690       <entry><type>int4</type></entry>
5691       <entry></entry>
5692       <entry><para>
5693        <structfield>typndims</structfield> is the number of array dimensions
5694        for a domain that is an array (that is, <structfield>typbasetype</> is
5695        an array type; the domain's <structfield>typelem</> will match the base
5696        type's <structfield>typelem</structfield>).
5697        Zero for types other than domains over array types.
5698        </para></entry>
5699      </row>
5700
5701      <row>
5702       <entry><structfield>typdefaultbin</structfield></entry>
5703       <entry><type>pg_node_tree</type></entry>
5704       <entry></entry>
5705       <entry><para>
5706        If <structfield>typdefaultbin</> is not null, it is the
5707        <function>nodeToString()</function>
5708        representation of a default expression for the type.  This is
5709        only used for domains.
5710       </para></entry>
5711      </row>
5712
5713      <row>
5714       <entry><structfield>typdefault</structfield></entry>
5715       <entry><type>text</type></entry>
5716       <entry></entry>
5717       <entry><para>
5718        <structfield>typdefault</> is null if the type has no associated
5719        default value. If <structfield>typdefaultbin</> is not null,
5720        <structfield>typdefault</> must contain a human-readable version of the
5721        default expression represented by <structfield>typdefaultbin</>.  If
5722        <structfield>typdefaultbin</> is null and <structfield>typdefault</> is
5723        not, then <structfield>typdefault</> is the external representation of
5724        the type's default value, which can be fed to the type's input
5725        converter to produce a constant.
5726       </para></entry>
5727      </row>
5728     </tbody>
5729    </tgroup>
5730   </table>
5731
5732   <para>
5733    <xref linkend="catalog-typcategory-table"> lists the system-defined values
5734    of <structfield>typcategory</>.  Any future additions to this list will
5735    also be upper-case ASCII letters.  All other ASCII characters are reserved
5736    for user-defined categories.
5737   </para>
5738
5739   <table id="catalog-typcategory-table">
5740    <title><structfield>typcategory</> Codes</title>
5741
5742    <tgroup cols="2">
5743     <thead>
5744      <row>
5745       <entry>Code</entry>
5746       <entry>Category</entry>
5747      </row>
5748     </thead>
5749
5750     <tbody>
5751      <row>
5752       <entry><literal>A</literal></entry>
5753       <entry>Array types</entry>
5754      </row>
5755      <row>
5756       <entry><literal>B</literal></entry>
5757       <entry>Boolean types</entry>
5758      </row>
5759      <row>
5760       <entry><literal>C</literal></entry>
5761       <entry>Composite types</entry>
5762      </row>
5763      <row>
5764       <entry><literal>D</literal></entry>
5765       <entry>Date/time types</entry>
5766      </row>
5767      <row>
5768       <entry><literal>E</literal></entry>
5769       <entry>Enum types</entry>
5770      </row>
5771      <row>
5772       <entry><literal>G</literal></entry>
5773       <entry>Geometric types</entry>
5774      </row>
5775      <row>
5776       <entry><literal>I</literal></entry>
5777       <entry>Network address types</entry>
5778      </row>
5779      <row>
5780       <entry><literal>N</literal></entry>
5781       <entry>Numeric types</entry>
5782      </row>
5783      <row>
5784       <entry><literal>P</literal></entry>
5785       <entry>Pseudo-types</entry>
5786      </row>
5787      <row>
5788       <entry><literal>S</literal></entry>
5789       <entry>String types</entry>
5790      </row>
5791      <row>
5792       <entry><literal>T</literal></entry>
5793       <entry>Timespan types</entry>
5794      </row>
5795      <row>
5796       <entry><literal>U</literal></entry>
5797       <entry>User-defined types</entry>
5798      </row>
5799      <row>
5800       <entry><literal>V</literal></entry>
5801       <entry>Bit-string types</entry>
5802      </row>
5803      <row>
5804       <entry><literal>X</literal></entry>
5805       <entry><type>unknown</> type</entry>
5806      </row>
5807     </tbody>
5808    </tgroup>
5809   </table>
5810
5811  </sect1>
5812
5813
5814  <sect1 id="catalog-pg-user-mapping">
5815   <title><structname>pg_user_mapping</structname></title>
5816
5817   <indexterm zone="catalog-pg-user-mapping">
5818    <primary>pg_user_mapping</primary>
5819   </indexterm>
5820
5821   <para>
5822    The catalog <structname>pg_user_mapping</structname> stores
5823    the mappings from local user to remote.  Access to this catalog is
5824    restricted from normal users, use the view
5825    <link linkend="view-pg-user-mappings"><structname>pg_user_mappings</structname></link>
5826    instead.
5827   </para>
5828
5829   <table>
5830    <title><structname>pg_user_mapping</> Columns</title>
5831
5832    <tgroup cols="4">
5833     <thead>
5834      <row>
5835       <entry>Name</entry>
5836       <entry>Type</entry>
5837       <entry>References</entry>
5838       <entry>Description</entry>
5839      </row>
5840     </thead>
5841
5842     <tbody>
5843      <row>
5844       <entry><structfield>umuser</structfield></entry>
5845       <entry><type>oid</type></entry>
5846       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
5847       <entry>OID of the local role being mapped, 0 if the user mapping is public</entry>
5848      </row>
5849
5850      <row>
5851       <entry><structfield>umserver</structfield></entry>
5852       <entry><type>oid</type></entry>
5853       <entry><literal><link linkend="catalog-pg-foreign-server"><structname>pg_foreign_server</structname></link>.oid</literal></entry>
5854       <entry>
5855        The OID of the foreign server that contains this mapping
5856       </entry>
5857      </row>
5858
5859      <row>
5860       <entry><structfield>umoptions</structfield></entry>
5861       <entry><type>text[]</type></entry>
5862       <entry></entry>
5863       <entry>
5864        User mapping specific options, as <quote>keyword=value</> strings
5865       </entry>
5866      </row>
5867     </tbody>
5868    </tgroup>
5869   </table>
5870  </sect1>
5871
5872
5873  <sect1 id="views-overview">
5874   <title>System Views</title>
5875
5876   <para>
5877    In addition to the system catalogs, <productname>PostgreSQL</productname>
5878    provides a number of built-in views.  Some system views provide convenient
5879    access to some commonly used queries on the system catalogs.  Other views
5880    provide access to internal server state.
5881   </para>
5882
5883   <para>
5884    The information schema (<xref linkend="information-schema">) provides
5885    an alternative set of views which overlap the functionality of the system
5886    views.  Since the information schema is SQL-standard whereas the views
5887    described here are <productname>PostgreSQL</productname>-specific,
5888    it's usually better to use the information schema if it provides all
5889    the information you need.
5890   </para>
5891
5892   <para>
5893    <xref linkend="view-table"> lists the system views described here.
5894    More detailed documentation of each view follows below.
5895    There are some additional views that provide access to the results of
5896    the statistics collector; they are described in <xref
5897    linkend="monitoring-stats-views-table">.
5898   </para>
5899
5900   <para>
5901    Except where noted, all the views described here are read-only.
5902   </para>
5903
5904   <table id="view-table">
5905    <title>System Views</title>
5906
5907    <tgroup cols="2">
5908     <thead>
5909      <row>
5910       <entry>View Name</entry>
5911       <entry>Purpose</entry>
5912      </row>
5913     </thead>
5914
5915     <tbody>
5916      <row>
5917       <entry><link linkend="view-pg-cursors"><structname>pg_cursors</structname></link></entry>
5918       <entry>open cursors</entry>
5919      </row>
5920
5921      <row>
5922       <entry><link linkend="view-pg-foreign-connections"><structname>pg_foreign_connections</structname></link></entry>
5923       <entry>established foreign connections</entry>
5924      </row>
5925
5926      <row>
5927       <entry><link linkend="view-pg-group"><structname>pg_group</structname></link></entry>
5928       <entry>groups of database users</entry>
5929      </row>
5930
5931      <row>
5932       <entry><link linkend="view-pg-indexes"><structname>pg_indexes</structname></link></entry>
5933       <entry>indexes</entry>
5934      </row>
5935
5936      <row>
5937       <entry><link linkend="view-pg-locks"><structname>pg_locks</structname></link></entry>
5938       <entry>currently held locks</entry>
5939      </row>
5940
5941      <row>
5942       <entry><link linkend="view-pg-prepared-statements"><structname>pg_prepared_statements</structname></link></entry>
5943       <entry>prepared statements</entry>
5944      </row>
5945
5946      <row>
5947       <entry><link linkend="view-pg-prepared-xacts"><structname>pg_prepared_xacts</structname></link></entry>
5948       <entry>prepared transactions</entry>
5949      </row>
5950
5951      <row>
5952       <entry><link linkend="view-pg-roles"><structname>pg_roles</structname></link></entry>
5953       <entry>database roles</entry>
5954      </row>
5955
5956      <row>
5957       <entry><link linkend="view-pg-rules"><structname>pg_rules</structname></link></entry>
5958       <entry>rules</entry>
5959      </row>
5960
5961      <row>
5962       <entry><link linkend="view-pg-settings"><structname>pg_settings</structname></link></entry>
5963       <entry>parameter settings</entry>
5964      </row>
5965
5966      <row>
5967       <entry><link linkend="view-pg-shadow"><structname>pg_shadow</structname></link></entry>
5968       <entry>database users</entry>
5969      </row>
5970
5971      <row>
5972       <entry><link linkend="view-pg-stats"><structname>pg_stats</structname></link></entry>
5973       <entry>planner statistics</entry>
5974      </row>
5975
5976      <row>
5977       <entry><link linkend="view-pg-tables"><structname>pg_tables</structname></link></entry>
5978       <entry>tables</entry>
5979      </row>
5980
5981      <row>
5982       <entry><link linkend="view-pg-timezone-abbrevs"><structname>pg_timezone_abbrevs</structname></link></entry>
5983       <entry>time zone abbreviations</entry>
5984      </row>
5985
5986      <row>
5987       <entry><link linkend="view-pg-timezone-names"><structname>pg_timezone_names</structname></link></entry>
5988       <entry>time zone names</entry>
5989      </row>
5990
5991      <row>
5992       <entry><link linkend="view-pg-user"><structname>pg_user</structname></link></entry>
5993       <entry>database users</entry>
5994      </row>
5995
5996      <row>
5997       <entry><link linkend="view-pg-views"><structname>pg_views</structname></link></entry>
5998       <entry>views</entry>
5999      </row>
6000
6001     </tbody>
6002    </tgroup>
6003   </table>
6004  </sect1>
6005
6006  <sect1 id="view-pg-cursors">
6007   <title><structname>pg_cursors</structname></title>
6008
6009   <indexterm zone="view-pg-cursors">
6010    <primary>pg_cursors</primary>
6011   </indexterm>
6012
6013   <para>
6014    The <structname>pg_cursors</structname> view lists the cursors that
6015    are currently available. Cursors can be defined in several ways:
6016    <itemizedlist>
6017     <listitem>
6018      <para>
6019       via the <xref linkend="sql-declare">
6020       statement in SQL
6021      </para>
6022     </listitem>
6023
6024     <listitem>
6025      <para>
6026       via the Bind message in the frontend/backend protocol, as
6027       described in <xref linkend="protocol-flow-ext-query">
6028      </para>
6029     </listitem>
6030
6031     <listitem>
6032      <para>
6033       via the Server Programming Interface (SPI), as described in
6034       <xref linkend="spi-interface">
6035      </para>
6036     </listitem>
6037    </itemizedlist>
6038
6039    The <structname>pg_cursors</structname> view displays cursors
6040    created by any of these means. Cursors only exist for the duration
6041    of the transaction that defines them, unless they have been
6042    declared <literal>WITH HOLD</literal>. Therefore non-holdable
6043    cursors are only present in the view until the end of their
6044    creating transaction.
6045
6046    <note>
6047     <para>
6048      Cursors are used internally to implement some of the components
6049      of <productname>PostgreSQL</>, such as procedural languages.
6050      Therefore, the <structname>pg_cursors</> view might include cursors
6051      that have not been explicitly created by the user.
6052     </para>
6053    </note>
6054   </para>
6055
6056   <table>
6057    <title><structname>pg_cursors</> Columns</title>
6058
6059    <tgroup cols="3">
6060     <thead>
6061      <row>
6062       <entry>Name</entry>
6063       <entry>Type</entry>
6064       <entry>Description</entry>
6065      </row>
6066     </thead>
6067
6068     <tbody>
6069      <row>
6070       <entry><structfield>name</structfield></entry>
6071       <entry><type>text</type></entry>
6072       <entry>The name of the cursor</entry>
6073      </row>
6074
6075      <row>
6076       <entry><structfield>statement</structfield></entry>
6077       <entry><type>text</type></entry>
6078       <entry>The verbatim query string submitted to declare this cursor</entry>
6079      </row>
6080
6081      <row>
6082       <entry><structfield>is_holdable</structfield></entry>
6083       <entry><type>boolean</type></entry>
6084       <entry>
6085        <literal>true</literal> if the cursor is holdable (that is, it
6086        can be accessed after the transaction that declared the cursor
6087        has committed); <literal>false</literal> otherwise
6088        </entry>
6089      </row>
6090
6091      <row>
6092       <entry><structfield>is_binary</structfield></entry>
6093       <entry><type>boolean</type></entry>
6094       <entry>
6095        <literal>true</literal> if the cursor was declared
6096        <literal>BINARY</literal>; <literal>false</literal>
6097        otherwise
6098        </entry>
6099      </row>
6100
6101      <row>
6102       <entry><structfield>is_scrollable</structfield></entry>
6103       <entry><type>boolean</type></entry>
6104       <entry>
6105        <literal>true</> if the cursor is scrollable (that is, it
6106        allows rows to be retrieved in a nonsequential manner);
6107        <literal>false</literal> otherwise
6108        </entry>
6109      </row>
6110
6111      <row>
6112       <entry><structfield>creation_time</structfield></entry>
6113       <entry><type>timestamptz</type></entry>
6114       <entry>The time at which the cursor was declared</entry>
6115      </row>
6116     </tbody>
6117    </tgroup>
6118   </table>
6119
6120   <para>
6121    The <structname>pg_cursors</structname> view is read only.
6122   </para>
6123
6124  </sect1>
6125
6126  <sect1 id="view-pg-foreign-connections">
6127   <title><structname>pg_foreign_connections</structname></title>
6128
6129   <indexterm zone="view-pg-foreign-connections">
6130    <primary>pg_foreign_connections</primary>
6131   </indexterm>
6132
6133   <para>
6134    The <structname>pg_foreign_connections</structname> view lists
6135    the foreign connections that are currently available.
6136    Foreign connections are established in several ways:
6137    <itemizedlist>
6138     <listitem>
6139      <para>
6140       via the query for a foreign table
6141      </para>
6142     </listitem>
6143
6144     <listitem>
6145      <para>
6146       via the use of dblink functions, see <xref linkend="dblink">
6147      </para>
6148     </listitem>
6149    </itemizedlist>
6150
6151    The <structname>pg_foreign_connections</structname> view displays
6152    foreign connections created by any of these means.
6153    Foreign connections only exist for the duration
6154    of the backend lifetime which established the connection,
6155    and cannot be used from other backends.
6156    Use <command>DISCARD ALL</command> command to close all foreign
6157    connections.
6158   </para>
6159
6160   <table>
6161    <title><structname>pg_foreign_connections</> Columns</title>
6162
6163    <tgroup cols="3">
6164     <thead>
6165      <row>
6166       <entry>Name</entry>
6167       <entry>Type</entry>
6168       <entry>Description</entry>
6169      </row>
6170     </thead>
6171
6172     <tbody>
6173      <row>
6174       <entry><structfield>conname</structfield></entry>
6175       <entry><type>text</type></entry>
6176       <entry>The name of the connection</entry>
6177      </row>
6178
6179      <row>
6180       <entry><structfield>srvname</structfield></entry>
6181       <entry><type>name</type></entry>
6182       <entry>The name of the foreign server which was used to
6183        establish the connection</entry>
6184      </row>
6185
6186      <row>
6187       <entry><structfield>usename</structfield></entry>
6188       <entry><type>name</type></entry>
6189       <entry>The name of the local user which was used to
6190        establish the connection</entry>
6191      </row>
6192
6193      <row>
6194       <entry><structfield>fdwname</structfield></entry>
6195       <entry><type>name</type></entry>
6196       <entry>The name of the foreign-data wrapper which was
6197       used to establish the connection</entry>
6198      </row>
6199     </tbody>
6200    </tgroup>
6201   </table>
6202
6203   <para>
6204    The <structname>pg_cursors</structname> view is read only.
6205   </para>
6206
6207  </sect1>
6208
6209  <sect1 id="view-pg-group">
6210   <title><structname>pg_group</structname></title>
6211
6212   <indexterm zone="view-pg-group">
6213    <primary>pg_group</primary>
6214   </indexterm>
6215
6216   <para>
6217    The view <structname>pg_group</structname> exists for backwards
6218    compatibility: it emulates a catalog that existed in
6219    <productname>PostgreSQL</productname> before version 8.1.
6220    It shows the names and members of all roles that are marked as not
6221    <structfield>rolcanlogin</>, which is an approximation to the set
6222    of roles that are being used as groups.
6223   </para>
6224
6225   <table>
6226    <title><structname>pg_group</> Columns</title>
6227
6228    <tgroup cols="4">
6229     <thead>
6230      <row>
6231       <entry>Name</entry>
6232       <entry>Type</entry>
6233       <entry>References</entry>
6234       <entry>Description</entry>
6235      </row>
6236     </thead>
6237
6238     <tbody>
6239      <row>
6240       <entry><structfield>groname</structfield></entry>
6241       <entry><type>name</type></entry>
6242       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.rolname</literal></entry>
6243       <entry>Name of the group</entry>
6244      </row>
6245
6246      <row>
6247       <entry><structfield>grosysid</structfield></entry>
6248       <entry><type>oid</type></entry>
6249       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
6250       <entry>ID of this group</entry>
6251      </row>
6252
6253      <row>
6254       <entry><structfield>grolist</structfield></entry>
6255       <entry><type>oid[]</type></entry>
6256       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
6257       <entry>An array containing the IDs of the roles in this group</entry>
6258      </row>
6259     </tbody>
6260    </tgroup>
6261   </table>
6262
6263  </sect1>
6264
6265  <sect1 id="view-pg-indexes">
6266   <title><structname>pg_indexes</structname></title>
6267
6268   <indexterm zone="view-pg-indexes">
6269    <primary>pg_indexes</primary>
6270   </indexterm>
6271
6272   <para>
6273    The view <structname>pg_indexes</structname> provides access to
6274    useful information about each index in the database.
6275   </para>
6276
6277   <table>
6278    <title><structname>pg_indexes</> Columns</title>
6279
6280    <tgroup cols="4">
6281     <thead>
6282      <row>
6283       <entry>Name</entry>
6284       <entry>Type</entry>
6285       <entry>References</entry>
6286       <entry>Description</entry>
6287      </row>
6288     </thead>
6289     <tbody>
6290      <row>
6291       <entry><structfield>schemaname</structfield></entry>
6292       <entry><type>name</type></entry>
6293       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.nspname</literal></entry>
6294       <entry>Name of schema containing table and index</entry>
6295      </row>
6296      <row>
6297       <entry><structfield>tablename</structfield></entry>
6298       <entry><type>name</type></entry>
6299       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.relname</literal></entry>
6300       <entry>Name of table the index is for</entry>
6301      </row>
6302      <row>
6303       <entry><structfield>indexname</structfield></entry>
6304       <entry><type>name</type></entry>
6305       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.relname</literal></entry>
6306       <entry>Name of index</entry>
6307      </row>
6308      <row>
6309       <entry><structfield>tablespace</structfield></entry>
6310       <entry><type>name</type></entry>
6311       <entry><literal><link linkend="catalog-pg-tablespace"><structname>pg_tablespace</structname></link>.spcname</literal></entry>
6312       <entry>Name of tablespace containing index (null if default for database)</entry>
6313      </row>
6314      <row>
6315       <entry><structfield>indexdef</structfield></entry>
6316       <entry><type>text</type></entry>
6317       <entry></entry>
6318       <entry>Index definition (a reconstructed <command>CREATE INDEX</command>
6319       command)</entry>
6320      </row>
6321     </tbody>
6322    </tgroup>
6323   </table>
6324
6325  </sect1>
6326
6327  <sect1 id="view-pg-locks">
6328   <title><structname>pg_locks</structname></title>
6329
6330   <indexterm zone="view-pg-locks">
6331    <primary>pg_locks</primary>
6332   </indexterm>
6333
6334   <para>
6335    The view <structname>pg_locks</structname> provides access to
6336    information about the locks held by open transactions within the
6337    database server.  See <xref linkend="mvcc"> for more discussion
6338    of locking.
6339   </para>
6340
6341   <para>
6342    <structname>pg_locks</structname> contains one row per active lockable
6343    object, requested lock mode, and relevant transaction.  Thus, the same
6344    lockable object might
6345    appear many times, if multiple transactions are holding or waiting
6346    for locks on it.  However, an object that currently has no locks on it
6347    will not appear at all.
6348   </para>
6349
6350   <para>
6351    There are several distinct types of lockable objects:
6352    whole relations (e.g., tables), individual pages of relations,
6353    individual tuples of relations,
6354    transaction IDs (both virtual and permanent IDs),
6355    and general database objects (identified by class OID and object OID,
6356    in the same way as in <structname>pg_description</structname> or
6357    <structname>pg_depend</structname>).  Also, the right to extend a
6358    relation is represented as a separate lockable object.
6359   </para>
6360
6361   <table>
6362    <title><structname>pg_locks</> Columns</title>
6363
6364    <tgroup cols="4">
6365     <thead>
6366      <row>
6367       <entry>Name</entry>
6368       <entry>Type</entry>
6369       <entry>References</entry>
6370       <entry>Description</entry>
6371      </row>
6372     </thead>
6373     <tbody>
6374      <row>
6375       <entry><structfield>locktype</structfield></entry>
6376       <entry><type>text</type></entry>
6377       <entry></entry>
6378       <entry>
6379        Type of the lockable object:
6380        <literal>relation</>,
6381        <literal>extend</>,
6382        <literal>page</>,
6383        <literal>tuple</>,
6384        <literal>transactionid</>,
6385        <literal>virtualxid</>,
6386        <literal>object</>,
6387        <literal>userlock</>, or
6388        <literal>advisory</>
6389       </entry>
6390      </row>
6391      <row>
6392       <entry><structfield>database</structfield></entry>
6393       <entry><type>oid</type></entry>
6394       <entry><literal><link linkend="catalog-pg-database"><structname>pg_database</structname></link>.oid</literal></entry>
6395       <entry>
6396        OID of the database in which the object exists, or
6397        zero if the object is a shared object, or
6398        null if the object is a transaction ID
6399       </entry>
6400      </row>
6401      <row>
6402       <entry><structfield>relation</structfield></entry>
6403       <entry><type>oid</type></entry>
6404       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
6405       <entry>
6406        OID of the relation, or null if the object is not
6407        a relation or part of a relation
6408       </entry>
6409      </row>
6410      <row>
6411       <entry><structfield>page</structfield></entry>
6412       <entry><type>integer</type></entry>
6413       <entry></entry>
6414       <entry>
6415        Page number within the relation, or null if the object
6416        is not a tuple or relation page
6417       </entry>
6418      </row>
6419      <row>
6420       <entry><structfield>tuple</structfield></entry>
6421       <entry><type>smallint</type></entry>
6422       <entry></entry>
6423       <entry>
6424        Tuple number within the page, or null if the object is not a tuple
6425       </entry>
6426      </row>
6427      <row>
6428       <entry><structfield>virtualxid</structfield></entry>
6429       <entry><type>text</type></entry>
6430       <entry></entry>
6431       <entry>
6432        Virtual ID of a transaction, or null if the object is not a
6433        virtual transaction ID
6434       </entry>
6435      </row>
6436      <row>
6437       <entry><structfield>transactionid</structfield></entry>
6438       <entry><type>xid</type></entry>
6439       <entry></entry>
6440       <entry>
6441        ID of a transaction, or null if the object is not a transaction ID
6442       </entry>
6443      </row>
6444      <row>
6445       <entry><structfield>classid</structfield></entry>
6446       <entry><type>oid</type></entry>
6447       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
6448       <entry>
6449        OID of the system catalog containing the object, or null if the
6450        object is not a general database object
6451       </entry>
6452      </row>
6453      <row>
6454       <entry><structfield>objid</structfield></entry>
6455       <entry><type>oid</type></entry>
6456       <entry>any OID column</entry>
6457       <entry>
6458        OID of the object within its system catalog, or null if the
6459        object is not a general database object.
6460        For advisory locks it is used to distinguish the two key
6461        spaces (<literal>1</> for an int8 key, <literal>2</> for two
6462        int4 keys).
6463       </entry>
6464      </row>
6465      <row>
6466       <entry><structfield>objsubid</structfield></entry>
6467       <entry><type>smallint</type></entry>
6468       <entry></entry>
6469       <entry>
6470        For a table column, this is the column number (the
6471        <structfield>classid</> and <structfield>objid</> refer to the
6472        table itself).  For all other object types, this column is
6473        zero.  Null if the object is not a general database object
6474       </entry>
6475      </row>
6476      <row>
6477       <entry><structfield>virtualtransaction</structfield></entry>
6478       <entry><type>text</type></entry>
6479       <entry></entry>
6480       <entry>
6481        Virtual ID of the transaction that is holding or awaiting this lock
6482       </entry>
6483      </row>
6484      <row>
6485       <entry><structfield>pid</structfield></entry>
6486       <entry><type>integer</type></entry>
6487       <entry></entry>
6488       <entry>
6489        Process ID of the server process holding or awaiting this
6490        lock.  Null if the lock is held by a prepared transaction.
6491       </entry>
6492      </row>
6493      <row>
6494       <entry><structfield>mode</structfield></entry>
6495       <entry><type>text</type></entry>
6496       <entry></entry>
6497       <entry>Name of the lock mode held or desired by this process (see <xref
6498       linkend="locking-tables">)</entry>
6499      </row>
6500      <row>
6501       <entry><structfield>granted</structfield></entry>
6502       <entry><type>boolean</type></entry>
6503       <entry></entry>
6504       <entry>True if lock is held, false if lock is awaited</entry>
6505      </row>
6506     </tbody>
6507    </tgroup>
6508   </table>
6509
6510   <para>
6511    <structfield>granted</structfield> is true in a row representing a lock
6512    held by the indicated transaction.  False indicates that this transaction is
6513    currently waiting to acquire this lock, which implies that some other
6514    transaction is holding a conflicting lock mode on the same lockable object.
6515    The waiting transaction will sleep until the other lock is released (or a
6516    deadlock situation is detected). A single transaction can be waiting to
6517    acquire at most one lock at a time.
6518   </para>
6519
6520   <para>
6521    Every transaction holds an exclusive lock on its virtual transaction ID for
6522    its entire duration.  If a permanent ID is assigned to the transaction
6523    (which normally happens only if the transaction changes the state of the
6524    database), it also holds an exclusive lock on its permanent transaction ID
6525    until it ends.  When one transaction finds it necessary to wait specifically
6526    for another transaction, it does so by attempting to acquire share lock on
6527    the other transaction ID (either virtual or permanent ID depending on the
6528    situation). That will succeed only when the other transaction
6529    terminates and releases its locks.
6530   </para>
6531
6532   <para>
6533    Although tuples are a lockable type of object,
6534    information about row-level locks is stored on disk, not in memory,
6535    and therefore row-level locks normally do not appear in this view.
6536    If a transaction is waiting for a
6537    row-level lock, it will usually appear in the view as waiting for the
6538    permanent transaction ID of the current holder of that row lock.
6539   </para>
6540
6541   <para>
6542    Advisory locks can be acquired on keys consisting of either a single
6543    <type>bigint</type> value or two integer values.  A <type>bigint</type> key is displayed with its
6544    high-order half in the <structfield>classid</> column, its low-order half
6545    in the <structfield>objid</> column, and <structfield>objsubid</> equal
6546    to 1.  Integer keys are displayed with the first key in the
6547    <structfield>classid</> column, the second key in the <structfield>objid</>
6548    column, and <structfield>objsubid</> equal to 2.  The actual meaning of
6549    the keys is up to the user.  Advisory locks are local to each database,
6550    so the <structfield>database</> column is meaningful for an advisory lock.
6551   </para>
6552
6553   <para>
6554    When the <structname>pg_locks</structname> view is accessed, the
6555    internal lock manager data structures are momentarily locked, and
6556    a copy is made for the view to display.  This ensures that the
6557    view produces a consistent set of results, while not blocking
6558    normal lock manager operations longer than necessary.  Nonetheless
6559    there could be some impact on database performance if this view is
6560    frequently accessed.
6561   </para>
6562
6563   <para>
6564    <structname>pg_locks</structname> provides a global view of all locks
6565    in the database cluster, not only those relevant to the current database.
6566    Although its <structfield>relation</structfield> column can be joined
6567    against <structname>pg_class</>.<structfield>oid</> to identify locked
6568    relations, this will only work correctly for relations in the current
6569    database (those for which the <structfield>database</structfield> column
6570    is either the current database's OID or zero).
6571   </para>
6572
6573   <para>
6574    The <structfield>pid</structfield> column can be joined to the
6575    <structfield>procpid</structfield> column of the
6576    <structname>pg_stat_activity</structname> view to get more
6577    information on the session holding or waiting to hold each lock.
6578    Also, if you are using prepared transactions, the
6579    <structfield>transaction</> column can be joined to the
6580    <structfield>transaction</structfield> column of the
6581    <structname>pg_prepared_xacts</structname> view to get more
6582    information on prepared transactions that hold locks.
6583    (A prepared transaction can never be waiting for a lock,
6584    but it continues to hold the locks it acquired while running.)
6585   </para>
6586
6587  </sect1>
6588
6589  <sect1 id="view-pg-prepared-statements">
6590   <title><structname>pg_prepared_statements</structname></title>
6591
6592   <indexterm zone="view-pg-prepared-statements">
6593    <primary>pg_prepared_statements</primary>
6594   </indexterm>
6595
6596   <para>
6597    The <structname>pg_prepared_statements</structname> view displays
6598    all the prepared statements that are available in the current
6599    session. See <xref linkend="sql-prepare"> for more information about prepared
6600    statements.
6601   </para>
6602
6603   <para>
6604    <structname>pg_prepared_statements</structname> contains one row
6605    for each prepared statement. Rows are added to the view when a new
6606    prepared statement is created and removed when a prepared statement
6607    is released (for example, via the <xref linkend="sql-deallocate"> command).
6608   </para>
6609
6610   <table>
6611    <title><structname>pg_prepared_statements</> Columns</title>
6612
6613    <tgroup cols="3">
6614     <thead>
6615      <row>
6616       <entry>Name</entry>
6617       <entry>Type</entry>
6618       <entry>Description</entry>
6619      </row>
6620     </thead>
6621     <tbody>
6622      <row>
6623       <entry><structfield>name</structfield></entry>
6624       <entry><type>text</type></entry>
6625       <entry>
6626        The identifier of the prepared statement
6627       </entry>
6628      </row>
6629      <row>
6630       <entry><structfield>statement</structfield></entry>
6631       <entry><type>text</type></entry>
6632       <entry>
6633        The query string submitted by the client to create this
6634        prepared statement. For prepared statements created via SQL,
6635        this is the <command>PREPARE</command> statement submitted by
6636        the client. For prepared statements created via the
6637        frontend/backend protocol, this is the text of the prepared
6638        statement itself.
6639       </entry>
6640      </row>
6641      <row>
6642       <entry><structfield>prepare_time</structfield></entry>
6643       <entry><type>timestamptz</type></entry>
6644       <entry>
6645        The time at which the prepared statement was created
6646       </entry>
6647      </row>
6648      <row>
6649       <entry><structfield>parameter_types</structfield></entry>
6650       <entry><type>regtype[]</type></entry>
6651       <entry>
6652        The expected parameter types for the prepared statement in the
6653        form of an array of <type>regtype</type>. The OID corresponding
6654        to an element of this array can be obtained by casting the
6655        <type>regtype</type> value to <type>oid</type>.
6656       </entry>
6657      </row>
6658      <row>
6659       <entry><structfield>from_sql</structfield></entry>
6660       <entry><type>boolean</type></entry>
6661       <entry>
6662        <literal>true</literal> if the prepared statement was created
6663        via the <command>PREPARE</command> SQL statement;
6664        <literal>false</literal> if the statement was prepared via the
6665        frontend/backend protocol
6666       </entry>
6667      </row>
6668     </tbody>
6669    </tgroup>
6670   </table>
6671
6672   <para>
6673    The <structname>pg_prepared_statements</structname> view is read only.
6674   </para>
6675  </sect1>
6676
6677  <sect1 id="view-pg-prepared-xacts">
6678   <title><structname>pg_prepared_xacts</structname></title>
6679
6680   <indexterm zone="view-pg-prepared-xacts">
6681    <primary>pg_prepared_xacts</primary>
6682   </indexterm>
6683
6684   <para>
6685    The view <structname>pg_prepared_xacts</structname> displays
6686    information about transactions that are currently prepared for two-phase
6687    commit (see <xref linkend="sql-prepare-transaction"> for details).
6688   </para>
6689
6690   <para>
6691    <structname>pg_prepared_xacts</structname> contains one row per prepared
6692    transaction.  An entry is removed when the transaction is committed or
6693    rolled back.
6694   </para>
6695
6696   <table>
6697    <title><structname>pg_prepared_xacts</> Columns</title>
6698
6699    <tgroup cols="4">
6700     <thead>
6701      <row>
6702       <entry>Name</entry>
6703       <entry>Type</entry>
6704       <entry>References</entry>
6705       <entry>Description</entry>
6706      </row>
6707     </thead>
6708     <tbody>
6709      <row>
6710       <entry><structfield>transaction</structfield></entry>
6711       <entry><type>xid</type></entry>
6712       <entry></entry>
6713       <entry>
6714        Numeric transaction identifier of the prepared transaction
6715       </entry>
6716      </row>
6717      <row>
6718       <entry><structfield>gid</structfield></entry>
6719       <entry><type>text</type></entry>
6720       <entry></entry>
6721       <entry>
6722        Global transaction identifier that was assigned to the transaction
6723       </entry>
6724      </row>
6725      <row>
6726       <entry><structfield>prepared</structfield></entry>
6727       <entry><type>timestamp with time zone</type></entry>
6728       <entry></entry>
6729       <entry>
6730        Time at which the transaction was prepared for commit
6731       </entry>
6732      </row>
6733      <row>
6734       <entry><structfield>owner</structfield></entry>
6735       <entry><type>name</type></entry>
6736       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.rolname</literal></entry>
6737       <entry>
6738        Name of the user that executed the transaction
6739       </entry>
6740      </row>
6741      <row>
6742       <entry><structfield>database</structfield></entry>
6743       <entry><type>name</type></entry>
6744       <entry><literal><link linkend="catalog-pg-database"><structname>pg_database</structname></link>.datname</literal></entry>
6745       <entry>
6746        Name of the database in which the transaction was executed
6747       </entry>
6748      </row>
6749     </tbody>
6750    </tgroup>
6751   </table>
6752
6753   <para>
6754    When the <structname>pg_prepared_xacts</structname> view is accessed, the
6755    internal transaction manager data structures are momentarily locked, and
6756    a copy is made for the view to display.  This ensures that the
6757    view produces a consistent set of results, while not blocking
6758    normal operations longer than necessary.  Nonetheless
6759    there could be some impact on database performance if this view is
6760    frequently accessed.
6761   </para>
6762
6763  </sect1>
6764
6765  <sect1 id="view-pg-roles">
6766   <title><structname>pg_roles</structname></title>
6767
6768   <indexterm zone="view-pg-roles">
6769    <primary>pg_roles</primary>
6770   </indexterm>
6771
6772   <para>
6773    The view <structname>pg_roles</structname> provides access to
6774    information about database roles.  This is simply a publicly
6775    readable view of
6776    <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>
6777    that blanks out the password field.
6778   </para>
6779
6780   <para>
6781    This view explicitly exposes the OID column of the underlying table,
6782    since that is needed to do joins to other catalogs.
6783   </para>
6784
6785   <table>
6786    <title><structname>pg_roles</> Columns</title>
6787
6788    <tgroup cols="4">
6789     <thead>
6790      <row>
6791       <entry>Name</entry>
6792       <entry>Type</entry>
6793       <entry>References</entry>
6794       <entry>Description</entry>
6795      </row>
6796     </thead>
6797
6798     <tbody>
6799      <row>
6800       <entry><structfield>rolname</structfield></entry>
6801       <entry><type>name</type></entry>
6802       <entry></entry>
6803       <entry>Role name</entry>
6804      </row>
6805
6806      <row>
6807       <entry><structfield>rolsuper</structfield></entry>
6808       <entry><type>bool</type></entry>
6809       <entry></entry>
6810       <entry>Role has superuser privileges</entry>
6811      </row>
6812
6813      <row>
6814       <entry><structfield>rolinherit</structfield></entry>
6815       <entry><type>bool</type></entry>
6816       <entry></entry>
6817       <entry>Role automatically inherits privileges of roles it is a
6818        member of</entry>
6819      </row>
6820
6821      <row>
6822       <entry><structfield>rolcreaterole</structfield></entry>
6823       <entry><type>bool</type></entry>
6824       <entry></entry>
6825       <entry>Role can create more roles</entry>
6826      </row>
6827
6828      <row>
6829       <entry><structfield>rolcreatedb</structfield></entry>
6830       <entry><type>bool</type></entry>
6831       <entry></entry>
6832       <entry>Role can create databases</entry>
6833      </row>
6834
6835      <row>
6836       <entry><structfield>rolcatupdate</structfield></entry>
6837       <entry><type>bool</type></entry>
6838       <entry></entry>
6839       <entry>
6840        Role can update system catalogs directly.  (Even a superuser cannot do
6841        this unless this column is true.)
6842       </entry>
6843      </row>
6844
6845      <row>
6846       <entry><structfield>rolcanlogin</structfield></entry>
6847       <entry><type>bool</type></entry>
6848       <entry></entry>
6849       <entry>
6850        Role can log in. That is, this role can be given as the initial
6851        session authorization identifier
6852       </entry>
6853      </row>
6854
6855      <row>
6856       <entry><structfield>rolconnlimit</structfield></entry>
6857       <entry><type>int4</type></entry>
6858       <entry></entry>
6859       <entry>
6860        For roles that can log in, this sets maximum number of concurrent
6861        connections this role can make.  -1 means no limit.
6862       </entry>
6863      </row>
6864
6865      <row>
6866       <entry><structfield>rolpassword</structfield></entry>
6867       <entry><type>text</type></entry>
6868       <entry></entry>
6869       <entry>Not the password (always reads as <literal>********</>)</entry>
6870      </row>
6871
6872      <row>
6873       <entry><structfield>rolvaliduntil</structfield></entry>
6874       <entry><type>timestamptz</type></entry>
6875       <entry></entry>
6876       <entry>Password expiry time (only used for password authentication);
6877        null if no expiration</entry>
6878      </row>
6879
6880      <row>
6881       <entry><structfield>oid</structfield></entry>
6882       <entry><type>oid</type></entry>
6883       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
6884       <entry>ID of role</entry>
6885      </row>
6886     </tbody>
6887    </tgroup>
6888   </table>
6889
6890  </sect1>
6891
6892  <sect1 id="view-pg-rules">
6893   <title><structname>pg_rules</structname></title>
6894
6895   <indexterm zone="view-pg-rules">
6896    <primary>pg_rules</primary>
6897   </indexterm>
6898
6899   <para>
6900    The view <structname>pg_rules</structname> provides access to
6901    useful information about query rewrite rules.
6902   </para>
6903
6904   <table>
6905    <title><structname>pg_rules</> Columns</title>
6906
6907    <tgroup cols="4">
6908     <thead>
6909      <row>
6910       <entry>Name</entry>
6911       <entry>Type</entry>
6912       <entry>References</entry>
6913       <entry>Description</entry>
6914      </row>
6915     </thead>
6916     <tbody>
6917      <row>
6918       <entry><structfield>schemaname</structfield></entry>
6919       <entry><type>name</type></entry>
6920       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.nspname</literal></entry>
6921       <entry>Name of schema containing table</entry>
6922      </row>
6923      <row>
6924       <entry><structfield>tablename</structfield></entry>
6925       <entry><type>name</type></entry>
6926       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.relname</literal></entry>
6927       <entry>Name of table the rule is for</entry>
6928      </row>
6929      <row>
6930       <entry><structfield>rulename</structfield></entry>
6931       <entry><type>name</type></entry>
6932       <entry><literal><link linkend="catalog-pg-rewrite"><structname>pg_rewrite</structname></link>.rulename</literal></entry>
6933       <entry>Name of rule</entry>
6934      </row>
6935      <row>
6936       <entry><structfield>definition</structfield></entry>
6937       <entry><type>text</type></entry>
6938       <entry></entry>
6939       <entry>Rule definition (a reconstructed creation command)</entry>
6940      </row>
6941     </tbody>
6942    </tgroup>
6943   </table>
6944
6945   <para>
6946    The <structname>pg_rules</> view excludes the <literal>ON SELECT</> rules
6947    of views; those can be seen in <structname>pg_views</>.
6948   </para>
6949
6950  </sect1>
6951
6952  <sect1 id="view-pg-settings">
6953   <title><structname>pg_settings</structname></title>
6954
6955   <indexterm zone="view-pg-settings">
6956    <primary>pg_settings</primary>
6957   </indexterm>
6958
6959   <para>
6960    The view <structname>pg_settings</structname> provides access to
6961    run-time parameters of the server.  It is essentially an alternative
6962    interface to the <xref linkend="sql-show">
6963    and <xref linkend="sql-set"> commands.
6964    It also provides access to some facts about each parameter that are
6965    not directly available from <command>SHOW</>, such as minimum and
6966    maximum values.
6967   </para>
6968
6969   <table>
6970    <title><structname>pg_settings</> Columns</title>
6971
6972    <tgroup cols="3">
6973     <thead>
6974      <row>
6975       <entry>Name</entry>
6976       <entry>Type</entry>
6977       <entry>Description</entry>
6978      </row>
6979     </thead>
6980     <tbody>
6981      <row>
6982       <entry><structfield>name</structfield></entry>
6983       <entry><type>text</type></entry>
6984       <entry>Run-time configuration parameter name</entry>
6985      </row>
6986      <row>
6987       <entry><structfield>setting</structfield></entry>
6988       <entry><type>text</type></entry>
6989       <entry>Current value of the parameter</entry>
6990      </row>
6991      <row>
6992       <entry><structfield>unit</structfield></entry>
6993       <entry><type>text</type></entry>
6994       <entry>Implicit unit of the parameter</entry>
6995      </row>
6996      <row>
6997       <entry><structfield>category</structfield></entry>
6998       <entry><type>text</type></entry>
6999       <entry>Logical group of the parameter</entry>
7000      </row>
7001      <row>
7002       <entry><structfield>short_desc</structfield></entry>
7003       <entry><type>text</type></entry>
7004       <entry>A brief description of the parameter</entry>
7005      </row>
7006      <row>
7007       <entry><structfield>extra_desc</structfield></entry>
7008       <entry><type>text</type></entry>
7009       <entry>Additional, more detailed, description of the parameter</entry>
7010      </row>
7011      <row>
7012       <entry><structfield>context</structfield></entry>
7013       <entry><type>text</type></entry>
7014       <entry>Context required to set the parameter's value</entry>
7015      </row>
7016      <row>
7017       <entry><structfield>vartype</structfield></entry>
7018       <entry><type>text</type></entry>
7019       <entry>Parameter type (<literal>bool</>, <literal>enum</>,
7020        <literal>integer</>, <literal>real</>, or <literal>string</>)
7021       </entry>
7022      </row>
7023      <row>
7024       <entry><structfield>source</structfield></entry>
7025       <entry><type>text</type></entry>
7026       <entry>Source of the current parameter value</entry>
7027      </row>
7028      <row>
7029       <entry><structfield>min_val</structfield></entry>
7030       <entry><type>text</type></entry>
7031       <entry>Minimum allowed value of the parameter (null for non-numeric
7032       values)</entry>
7033      </row>
7034      <row>
7035       <entry><structfield>max_val</structfield></entry>
7036       <entry><type>text</type></entry>
7037       <entry>Maximum allowed value of the parameter (null for non-numeric
7038       values)</entry>
7039      </row>
7040      <row>
7041       <entry><structfield>enumvals</structfield></entry>
7042       <entry><type>text[]</type></entry>
7043       <entry>Allowed values of an enum parameter (null for non-enum
7044       values)</entry>
7045      </row>
7046      <row>
7047       <entry><structfield>boot_val</structfield></entry>
7048       <entry><type>text</type></entry>
7049       <entry>Parameter value assumed at server startup if the parameter is
7050       not otherwise set</entry>
7051      </row>
7052      <row>
7053       <entry><structfield>reset_val</structfield></entry>
7054       <entry><type>text</type></entry>
7055       <entry>Value that <command>RESET</command> would reset the parameter to
7056       in the current session</entry>
7057      </row>
7058      <row>
7059       <entry><structfield>sourcefile</structfield></entry>
7060       <entry><type>text</type></entry>
7061       <entry>Configuration file the current value was set in (null for
7062       values set from sources other than configuration files, or when
7063       examined by a non-superuser);
7064       helpful when using <literal>include</> directives in configuration files</entry>
7065      </row>
7066      <row>
7067       <entry><structfield>sourceline</structfield></entry>
7068       <entry><type>integer</type></entry>
7069       <entry>Line number within the configuration file the current value was
7070       set at (null for values set from sources other than configuration files,
7071       or when examined by a non-superuser)
7072       </entry>
7073      </row>
7074     </tbody>
7075    </tgroup>
7076   </table>
7077
7078   <para>
7079    The <structname>pg_settings</structname> view cannot be inserted into or
7080    deleted from, but it can be updated.  An <command>UPDATE</command> applied
7081    to a row of <structname>pg_settings</structname> is equivalent to executing
7082    the <xref linkend="sql-set"> command on that named
7083    parameter. The change only affects the value used by the current
7084    session. If an <command>UPDATE</command> is issued within a transaction
7085    that is later aborted, the effects of the <command>UPDATE</command> command
7086    disappear when the transaction is rolled back. Once the surrounding
7087    transaction is committed, the effects will persist until the end of the
7088    session, unless overridden by another <command>UPDATE</command> or
7089    <command>SET</command>.
7090   </para>
7091
7092  </sect1>
7093
7094  <sect1 id="view-pg-shadow">
7095   <title><structname>pg_shadow</structname></title>
7096
7097   <indexterm zone="view-pg-shadow">
7098    <primary>pg_shadow</primary>
7099   </indexterm>
7100
7101   <para>
7102    The view <structname>pg_shadow</structname> exists for backwards
7103    compatibility: it emulates a catalog that existed in
7104    <productname>PostgreSQL</productname> before version 8.1.
7105    It shows properties of all roles that are marked as
7106    <structfield>rolcanlogin</> in
7107    <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.
7108   </para>
7109
7110   <para>
7111    The name stems from the fact that this table
7112    should not be readable by the public since it contains passwords.
7113    <link linkend="view-pg-user"><structname>pg_user</structname></link>
7114    is a publicly readable view on
7115    <structname>pg_shadow</structname> that blanks out the password field.
7116   </para>
7117
7118   <table>
7119    <title><structname>pg_shadow</> Columns</title>
7120
7121    <tgroup cols="4">
7122     <thead>
7123      <row>
7124       <entry>Name</entry>
7125       <entry>Type</entry>
7126       <entry>References</entry>
7127       <entry>Description</entry>
7128      </row>
7129     </thead>
7130
7131     <tbody>
7132      <row>
7133       <entry><structfield>usename</structfield></entry>
7134       <entry><type>name</type></entry>
7135       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.rolname</literal></entry>
7136       <entry>User name</entry>
7137      </row>
7138
7139      <row>
7140       <entry><structfield>usesysid</structfield></entry>
7141       <entry><type>oid</type></entry>
7142       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
7143       <entry>ID of this user</entry>
7144      </row>
7145
7146      <row>
7147       <entry><structfield>usecreatedb</structfield></entry>
7148       <entry><type>bool</type></entry>
7149       <entry></entry>
7150       <entry>User can create databases</entry>
7151      </row>
7152
7153      <row>
7154       <entry><structfield>usesuper</structfield></entry>
7155       <entry><type>bool</type></entry>
7156       <entry></entry>
7157       <entry>User is a superuser</entry>
7158      </row>
7159
7160      <row>
7161       <entry><structfield>usecatupd</structfield></entry>
7162       <entry><type>bool</type></entry>
7163       <entry></entry>
7164       <entry>
7165        User can update system catalogs.  (Even a superuser cannot do
7166        this unless this column is true.)
7167       </entry>
7168      </row>
7169
7170      <row>
7171       <entry><structfield>passwd</structfield></entry>
7172       <entry><type>text</type></entry>
7173       <entry></entry>
7174       <entry>Password (possibly encrypted); null if none.  See
7175       <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>
7176       for details of how encrypted passwords are stored.</entry>
7177      </row>
7178
7179      <row>
7180       <entry><structfield>valuntil</structfield></entry>
7181       <entry><type>abstime</type></entry>
7182       <entry></entry>
7183       <entry>Password expiry time (only used for password authentication)</entry>
7184      </row>
7185
7186      <row>
7187       <entry><structfield>useconfig</structfield></entry>
7188       <entry><type>text[]</type></entry>
7189       <entry></entry>
7190       <entry>Session defaults for run-time configuration variables</entry>
7191      </row>
7192     </tbody>
7193    </tgroup>
7194   </table>
7195
7196  </sect1>
7197
7198  <sect1 id="view-pg-stats">
7199   <title><structname>pg_stats</structname></title>
7200
7201   <indexterm zone="view-pg-stats">
7202    <primary>pg_stats</primary>
7203   </indexterm>
7204
7205   <para>
7206    The view <structname>pg_stats</structname> provides access to
7207    the information stored in the <link
7208    linkend="catalog-pg-statistic"><structname>pg_statistic</structname></link>
7209    catalog.  This view allows access only to rows of
7210    <structname>pg_statistic</structname> that correspond to tables the
7211    user has permission to read, and therefore it is safe to allow public
7212    read access to this view.
7213   </para>
7214
7215   <para>
7216    <structname>pg_stats</structname> is also designed to present the
7217    information in a more readable format than the underlying catalog
7218    &mdash; at the cost that its schema must be extended whenever new slot types
7219    are defined for <structname>pg_statistic</structname>.
7220   </para>
7221
7222   <table>
7223    <title><structname>pg_stats</> Columns</title>
7224
7225    <tgroup cols="4">
7226     <thead>
7227      <row>
7228       <entry>Name</entry>
7229       <entry>Type</entry>
7230       <entry>References</entry>
7231       <entry>Description</entry>
7232      </row>
7233     </thead>
7234     <tbody>
7235      <row>
7236       <entry><structfield>schemaname</structfield></entry>
7237       <entry><type>name</type></entry>
7238       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.nspname</literal></entry>
7239       <entry>Name of schema containing table</entry>
7240      </row>
7241
7242      <row>
7243       <entry><structfield>tablename</structfield></entry>
7244       <entry><type>name</type></entry>
7245       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.relname</literal></entry>
7246       <entry>Name of table</entry>
7247      </row>
7248
7249      <row>
7250       <entry><structfield>attname</structfield></entry>
7251       <entry><type>name</type></entry>
7252       <entry><literal><link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.attname</literal></entry>
7253       <entry>Name of the column described by this row</entry>
7254      </row>
7255
7256      <row>
7257       <entry><structfield>inherited</structfield></entry>
7258       <entry><type>bool</type></entry>
7259       <entry></entry>
7260       <entry>If true, this row includes inheritance child columns, not just the
7261        values in the specified table</entry>
7262      </row>
7263
7264      <row>
7265       <entry><structfield>null_frac</structfield></entry>
7266       <entry><type>real</type></entry>
7267       <entry></entry>
7268       <entry>Fraction of column entries that are null</entry>
7269      </row>
7270
7271      <row>
7272       <entry><structfield>avg_width</structfield></entry>
7273       <entry><type>integer</type></entry>
7274       <entry></entry>
7275       <entry>Average width in bytes of column's entries</entry>
7276      </row>
7277
7278      <row>
7279       <entry><structfield>n_distinct</structfield></entry>
7280       <entry><type>real</type></entry>
7281       <entry></entry>
7282       <entry>
7283        If greater than zero, the estimated number of distinct values in the
7284        column.  If less than zero, the negative of the number of distinct
7285        values divided by the number of rows.  (The negated form is used when
7286        <command>ANALYZE</> believes that the number of distinct values is
7287        likely to increase as the table grows; the positive form is used when
7288        the column seems to have a fixed number of possible values.)  For
7289        example, -1 indicates a unique column in which the number of distinct
7290        values is the same as the number of rows.
7291       </entry>
7292      </row>
7293
7294      <row>
7295       <entry><structfield>most_common_vals</structfield></entry>
7296       <entry><type>anyarray</type></entry>
7297       <entry></entry>
7298       <entry>
7299        A list of the most common values in the column. (Null if
7300        no values seem to be more common than any others.)
7301        For some data types such as <type>tsvector</>, this is a list of
7302        the most common element values rather than values of the type itself.
7303       </entry>
7304      </row>
7305
7306      <row>
7307       <entry><structfield>most_common_freqs</structfield></entry>
7308       <entry><type>real[]</type></entry>
7309       <entry></entry>
7310       <entry>
7311        A list of the frequencies of the most common values or elements,
7312        i.e., number of occurrences of each divided by total number of rows.
7313        (Null when <structfield>most_common_vals</structfield> is.)
7314        For some data types such as <type>tsvector</>, it can also store some
7315        additional information, making it longer than the
7316        <structfield>most_common_vals</> array.
7317       </entry>
7318      </row>
7319
7320      <row>
7321       <entry><structfield>histogram_bounds</structfield></entry>
7322       <entry><type>anyarray</type></entry>
7323       <entry></entry>
7324       <entry>
7325        A list of values that divide the column's values into groups of
7326        approximately equal population.  The values in
7327        <structfield>most_common_vals</>, if present, are omitted from this
7328        histogram calculation.  (This column is null if the column data type
7329        does not have a <literal>&lt;</> operator or if the
7330        <structfield>most_common_vals</> list accounts for the entire
7331        population.)
7332       </entry>
7333      </row>
7334
7335      <row>
7336       <entry><structfield>correlation</structfield></entry>
7337       <entry><type>real</type></entry>
7338       <entry></entry>
7339       <entry>
7340        Statistical correlation between physical row ordering and
7341        logical ordering of the column values.  This ranges from -1 to +1.
7342        When the value is near -1 or +1, an index scan on the column will
7343        be estimated to be cheaper than when it is near zero, due to reduction
7344        of random access to the disk.  (This column is null if the column data
7345        type does not have a <literal>&lt;</> operator.)
7346       </entry>
7347      </row>
7348     </tbody>
7349    </tgroup>
7350   </table>
7351
7352   <para>
7353    The maximum number of entries in the <structfield>most_common_vals</>
7354    and <structfield>histogram_bounds</> arrays can be set on a
7355    column-by-column basis using the <command>ALTER TABLE SET STATISTICS</>
7356    command, or globally by setting the
7357    <xref linkend="guc-default-statistics-target"> run-time parameter.
7358   </para>
7359
7360  </sect1>
7361
7362  <sect1 id="view-pg-tables">
7363   <title><structname>pg_tables</structname></title>
7364
7365   <indexterm zone="view-pg-tables">
7366    <primary>pg_tables</primary>
7367   </indexterm>
7368
7369   <para>
7370    The view <structname>pg_tables</structname> provides access to
7371    useful information about each table in the database.
7372   </para>
7373
7374   <table>
7375    <title><structname>pg_tables</> Columns</title>
7376
7377    <tgroup cols="4">
7378     <thead>
7379      <row>
7380       <entry>Name</entry>
7381       <entry>Type</entry>
7382       <entry>References</entry>
7383       <entry>Description</entry>
7384      </row>
7385     </thead>
7386     <tbody>
7387      <row>
7388       <entry><structfield>schemaname</structfield></entry>
7389       <entry><type>name</type></entry>
7390       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.nspname</literal></entry>
7391       <entry>Name of schema containing table</entry>
7392      </row>
7393      <row>
7394       <entry><structfield>tablename</structfield></entry>
7395       <entry><type>name</type></entry>
7396       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.relname</literal></entry>
7397       <entry>Name of table</entry>
7398      </row>
7399      <row>
7400       <entry><structfield>tableowner</structfield></entry>
7401       <entry><type>name</type></entry>
7402       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.rolname</literal></entry>
7403       <entry>Name of table's owner</entry>
7404      </row>
7405      <row>
7406       <entry><structfield>tablespace</structfield></entry>
7407       <entry><type>name</type></entry>
7408       <entry><literal><link linkend="catalog-pg-tablespace"><structname>pg_tablespace</structname></link>.spcname</literal></entry>
7409       <entry>Name of tablespace containing table (null if default for database)</entry>
7410      </row>
7411      <row>
7412       <entry><structfield>hasindexes</structfield></entry>
7413       <entry><type>boolean</type></entry>
7414       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.relhasindex</literal></entry>
7415       <entry>True if table has (or recently had) any indexes</entry>
7416      </row>
7417      <row>
7418       <entry><structfield>hasrules</structfield></entry>
7419       <entry><type>boolean</type></entry>
7420       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.relhasrules</literal></entry>
7421       <entry>True if table has (or once had) rules</entry>
7422      </row>
7423      <row>
7424       <entry><structfield>hastriggers</structfield></entry>
7425       <entry><type>boolean</type></entry>
7426       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.relhastriggers</literal></entry>
7427       <entry>True if table has (or once had) triggers</entry>
7428      </row>
7429     </tbody>
7430    </tgroup>
7431   </table>
7432
7433  </sect1>
7434
7435  <sect1 id="view-pg-timezone-abbrevs">
7436   <title><structname>pg_timezone_abbrevs</structname></title>
7437
7438   <indexterm zone="view-pg-timezone-abbrevs">
7439    <primary>pg_timezone_abbrevs</primary>
7440   </indexterm>
7441
7442   <para>
7443    The view <structname>pg_timezone_abbrevs</structname> provides a list
7444    of time zone abbreviations that are currently recognized by the datetime
7445    input routines.  The contents of this view change when the
7446    <xref linkend="guc-timezone-abbreviations"> run-time parameter is modified.
7447   </para>
7448
7449   <table>
7450    <title><structname>pg_timezone_abbrevs</> Columns</title>
7451
7452    <tgroup cols="3">
7453     <thead>
7454      <row>
7455       <entry>Name</entry>
7456       <entry>Type</entry>
7457       <entry>Description</entry>
7458      </row>
7459     </thead>
7460     <tbody>
7461      <row>
7462       <entry><structfield>abbrev</structfield></entry>
7463       <entry><type>text</type></entry>
7464       <entry>Time zone abbreviation</entry>
7465      </row>
7466      <row>
7467       <entry><structfield>utc_offset</structfield></entry>
7468       <entry><type>interval</type></entry>
7469       <entry>Offset from UTC (positive means east of Greenwich)</entry>
7470      </row>
7471      <row>
7472       <entry><structfield>is_dst</structfield></entry>
7473       <entry><type>boolean</type></entry>
7474       <entry>True if this is a daylight-savings abbreviation</entry>
7475      </row>
7476     </tbody>
7477    </tgroup>
7478   </table>
7479
7480  </sect1>
7481
7482  <sect1 id="view-pg-timezone-names">
7483   <title><structname>pg_timezone_names</structname></title>
7484
7485   <indexterm zone="view-pg-timezone-names">
7486    <primary>pg_timezone_names</primary>
7487   </indexterm>
7488
7489   <para>
7490    The view <structname>pg_timezone_names</structname> provides a list
7491    of time zone names that are recognized by <command>SET TIMEZONE</>,
7492    along with their associated abbreviations, UTC offsets,
7493    and daylight-savings status.
7494    Unlike the abbreviations shown in <link
7495    linkend="view-pg-timezone-abbrevs"><structname>pg_timezone_abbrevs</structname></link>, many of these names imply a set of daylight-savings transition
7496    date rules.  Therefore, the associated information changes across local DST
7497    boundaries.  The displayed information is computed based on the current
7498    value of <function>CURRENT_TIMESTAMP</>.
7499   </para>
7500
7501   <table>
7502    <title><structname>pg_timezone_names</> Columns</title>
7503
7504    <tgroup cols="3">
7505     <thead>
7506      <row>
7507       <entry>Name</entry>
7508       <entry>Type</entry>
7509       <entry>Description</entry>
7510      </row>
7511     </thead>
7512     <tbody>
7513      <row>
7514       <entry><structfield>name</structfield></entry>
7515       <entry><type>text</type></entry>
7516       <entry>Time zone name</entry>
7517      </row>
7518      <row>
7519       <entry><structfield>abbrev</structfield></entry>
7520       <entry><type>text</type></entry>
7521       <entry>Time zone abbreviation</entry>
7522      </row>
7523      <row>
7524       <entry><structfield>utc_offset</structfield></entry>
7525       <entry><type>interval</type></entry>
7526       <entry>Offset from UTC (positive means east of Greenwich)</entry>
7527      </row>
7528      <row>
7529       <entry><structfield>is_dst</structfield></entry>
7530       <entry><type>boolean</type></entry>
7531       <entry>True if currently observing daylight savings</entry>
7532      </row>
7533     </tbody>
7534    </tgroup>
7535   </table>
7536
7537  </sect1>
7538
7539  <sect1 id="view-pg-user">
7540   <title><structname>pg_user</structname></title>
7541
7542   <indexterm zone="view-pg-user">
7543    <primary>pg_user</primary>
7544   </indexterm>
7545
7546   <para>
7547    The view <structname>pg_user</structname> provides access to
7548    information about database users.  This is simply a publicly
7549    readable view of
7550    <link linkend="view-pg-shadow"><structname>pg_shadow</structname></link>
7551    that blanks out the password field.
7552   </para>
7553
7554   <table>
7555    <title><structname>pg_user</> Columns</title>
7556
7557    <tgroup cols="3">
7558     <thead>
7559      <row>
7560       <entry>Name</entry>
7561       <entry>Type</entry>
7562       <entry>Description</entry>
7563      </row>
7564     </thead>
7565     <tbody>
7566      <row>
7567       <entry><structfield>usename</structfield></entry>
7568       <entry><type>name</type></entry>
7569       <entry>User name</entry>
7570      </row>
7571
7572      <row>
7573       <entry><structfield>usesysid</structfield></entry>
7574       <entry><type>int4</type></entry>
7575       <entry>User ID (arbitrary number used to reference this user)</entry>
7576      </row>
7577
7578      <row>
7579       <entry><structfield>usecreatedb</structfield></entry>
7580       <entry><type>bool</type></entry>
7581       <entry>User can create databases</entry>
7582      </row>
7583
7584      <row>
7585       <entry><structfield>usesuper</structfield></entry>
7586       <entry><type>bool</type></entry>
7587       <entry>User is a superuser</entry>
7588      </row>
7589
7590      <row>
7591       <entry><structfield>usecatupd</structfield></entry>
7592       <entry><type>bool</type></entry>
7593       <entry>
7594        User can update system catalogs.  (Even a superuser cannot do
7595        this unless this column is true.)
7596       </entry>
7597      </row>
7598
7599      <row>
7600       <entry><structfield>passwd</structfield></entry>
7601       <entry><type>text</type></entry>
7602       <entry>Not the password (always reads as <literal>********</>)</entry>
7603      </row>
7604
7605      <row>
7606       <entry><structfield>valuntil</structfield></entry>
7607       <entry><type>abstime</type></entry>
7608       <entry>Password expiry time (only used for password authentication)</entry>
7609      </row>
7610
7611      <row>
7612       <entry><structfield>useconfig</structfield></entry>
7613       <entry><type>text[]</type></entry>
7614       <entry>Session defaults for run-time configuration variables</entry>
7615      </row>
7616     </tbody>
7617    </tgroup>
7618   </table>
7619
7620  </sect1>
7621
7622  <sect1 id="view-pg-user-mappings">
7623   <title><structname>pg_user_mappings</structname></title>
7624
7625   <indexterm zone="view-pg-user-mappings">
7626    <primary>pg_user_mappings</primary>
7627   </indexterm>
7628
7629   <para>
7630    The view <structname>pg_user_mappings</structname> provides access
7631    to information about user mappings.  This is essentially a publicly
7632    readable view of
7633    <link linkend="catalog-pg-user-mapping"><structname>pg_user_mapping</structname></link>
7634    that leaves out the options field if the user has no rights to use
7635    it.
7636   </para>
7637
7638   <table>
7639    <title><structname>pg_user_mappings</> Columns</title>
7640
7641    <tgroup cols="4">
7642     <thead>
7643      <row>
7644       <entry>Name</entry>
7645       <entry>Type</entry>
7646       <entry>References</entry>
7647       <entry>Description</entry>
7648      </row>
7649     </thead>
7650
7651     <tbody>
7652      <row>
7653       <entry><structfield>umid</structfield></entry>
7654       <entry><type>oid</type></entry>
7655       <entry><literal><link linkend="catalog-pg-user-mapping"><structname>pg_user_mapping</structname></link>.oid</literal></entry>
7656       <entry>OID of the user mapping</entry>
7657      </row>
7658
7659      <row>
7660       <entry><structfield>srvid</structfield></entry>
7661       <entry><type>oid</type></entry>
7662       <entry><literal><link linkend="catalog-pg-foreign-server"><structname>pg_foreign_server</structname></link>.oid</literal></entry>
7663       <entry>
7664        The OID of the foreign server that contains this mapping
7665       </entry>
7666      </row>
7667
7668      <row>
7669       <entry><structfield>srvname</structfield></entry>
7670       <entry><type>text</type></entry>
7671       <entry></entry>
7672       <entry>
7673        Name of the foreign server
7674       </entry>
7675      </row>
7676
7677      <row>
7678       <entry><structfield>umuser</structfield></entry>
7679       <entry><type>oid</type></entry>
7680       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
7681       <entry>OID of the local role being mapped, 0 if the user mapping is public</entry>
7682      </row>
7683
7684      <row>
7685       <entry><structfield>usename</structfield></entry>
7686       <entry><type>name</type></entry>
7687       <entry></entry>
7688       <entry>Name of the local user to be mapped</entry>
7689      </row>
7690
7691      <row>
7692       <entry><structfield>umoptions</structfield></entry>
7693       <entry><type>text[]</type></entry>
7694       <entry></entry>
7695       <entry>
7696        User mapping specific options, as <quote>keyword=value</>
7697        strings, if the current user is the owner of the foreign
7698        server, else null
7699       </entry>
7700      </row>
7701     </tbody>
7702    </tgroup>
7703   </table>
7704  </sect1>
7705
7706
7707  <sect1 id="view-pg-views">
7708   <title><structname>pg_views</structname></title>
7709
7710   <indexterm zone="view-pg-views">
7711    <primary>pg_views</primary>
7712   </indexterm>
7713
7714   <para>
7715    The view <structname>pg_views</structname> provides access to
7716    useful information about each view in the database.
7717   </para>
7718
7719   <table>
7720    <title><structname>pg_views</> Columns</title>
7721
7722    <tgroup cols="4">
7723     <thead>
7724      <row>
7725       <entry>Name</entry>
7726       <entry>Type</entry>
7727       <entry>References</entry>
7728       <entry>Description</entry>
7729      </row>
7730     </thead>
7731     <tbody>
7732      <row>
7733       <entry><structfield>schemaname</structfield></entry>
7734       <entry><type>name</type></entry>
7735       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.nspname</literal></entry>
7736       <entry>Name of schema containing view</entry>
7737      </row>
7738      <row>
7739       <entry><structfield>viewname</structfield></entry>
7740       <entry><type>name</type></entry>
7741       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.relname</literal></entry>
7742       <entry>Name of view</entry>
7743      </row>
7744      <row>
7745       <entry><structfield>viewowner</structfield></entry>
7746       <entry><type>name</type></entry>
7747       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.rolname</literal></entry>
7748       <entry>Name of view's owner</entry>
7749      </row>
7750      <row>
7751       <entry><structfield>definition</structfield></entry>
7752       <entry><type>text</type></entry>
7753       <entry></entry>
7754       <entry>View definition (a reconstructed <command>SELECT</command> query)</entry>
7755      </row>
7756     </tbody>
7757    </tgroup>
7758   </table>
7759
7760  </sect1>
7761
7762 </chapter>