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