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, or zero if none</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, or zero if none</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>relistemp</structfield></entry>
1537       <entry><type>bool</type></entry>
1538       <entry></entry>
1539       <entry>
1540        True if this table is a temporary relation.  If so, only the creating
1541        session can safely access its contents
1542       </entry>
1543      </row>
1544
1545      <row>
1546       <entry><structfield>relkind</structfield></entry>
1547       <entry><type>char</type></entry>
1548       <entry></entry>
1549       <entry>
1550        <literal>r</> = ordinary table, <literal>i</> = index,
1551        <literal>S</> = sequence, <literal>v</> = view, <literal>c</> =
1552        composite type, <literal>t</> = TOAST
1553        table
1554       </entry>
1555      </row>
1556
1557      <row>
1558       <entry><structfield>relnatts</structfield></entry>
1559       <entry><type>int2</type></entry>
1560       <entry></entry>
1561       <entry>
1562        Number of user columns in the relation (system columns not
1563        counted).  There must be this many corresponding entries in
1564        <structname>pg_attribute</structname>.  See also
1565        <literal>pg_attribute.attnum</literal>
1566       </entry>
1567      </row>
1568
1569      <row>
1570       <entry><structfield>relchecks</structfield></entry>
1571       <entry><type>int2</type></entry>
1572       <entry></entry>
1573       <entry>
1574        Number of <literal>CHECK</> constraints on the table; see
1575        <link linkend="catalog-pg-constraint"><structname>pg_constraint</structname></link> catalog
1576       </entry>
1577      </row>
1578
1579      <row>
1580       <entry><structfield>relhasoids</structfield></entry>
1581       <entry><type>bool</type></entry>
1582       <entry></entry>
1583       <entry>
1584        True if we generate an OID for each row of the relation
1585       </entry>
1586      </row>
1587
1588      <row>
1589       <entry><structfield>relhaspkey</structfield></entry>
1590       <entry><type>bool</type></entry>
1591       <entry></entry>
1592       <entry>
1593        True if the table has (or once had) a primary key
1594       </entry>
1595      </row>
1596
1597      <row>
1598       <entry><structfield>relhasrules</structfield></entry>
1599       <entry><type>bool</type></entry>
1600       <entry></entry>
1601       <entry>
1602        True if table has (or once had) rules; see
1603        <link linkend="catalog-pg-rewrite"><structname>pg_rewrite</structname></link> catalog
1604       </entry>
1605      </row>
1606
1607      <row>
1608       <entry><structfield>relhastriggers</structfield></entry>
1609       <entry><type>bool</type></entry>
1610       <entry></entry>
1611       <entry>
1612        True if table has (or once had) triggers; see
1613        <link linkend="catalog-pg-trigger"><structname>pg_trigger</structname></link> catalog
1614       </entry>
1615      </row>
1616
1617      <row>
1618       <entry><structfield>relhassubclass</structfield></entry>
1619       <entry><type>bool</type></entry>
1620       <entry></entry>
1621       <entry>True if table has (or once had) any inheritance children</entry>
1622      </row>
1623
1624      <row>
1625       <entry><structfield>relfrozenxid</structfield></entry>
1626       <entry><type>xid</type></entry>
1627       <entry></entry>
1628       <entry>
1629        All transaction IDs before this one have been replaced with a permanent
1630        (<quote>frozen</>) transaction ID in this table.  This is used to track
1631        whether the table needs to be vacuumed in order to prevent transaction
1632        ID wraparound or to allow <literal>pg_clog</> to be shrunk.  Zero
1633        (<symbol>InvalidTransactionId</symbol>) if the relation is not a table
1634       </entry>
1635      </row>
1636
1637      <row>
1638       <entry><structfield>relacl</structfield></entry>
1639       <entry><type>aclitem[]</type></entry>
1640       <entry></entry>
1641       <entry>
1642        Access privileges; see
1643        <xref linkend="sql-grant" endterm="sql-grant-title"> and
1644        <xref linkend="sql-revoke" endterm="sql-revoke-title">
1645        for details
1646       </entry>
1647      </row>
1648
1649      <row>
1650       <entry><structfield>reloptions</structfield></entry>
1651       <entry><type>text[]</type></entry>
1652       <entry></entry>
1653       <entry>
1654        Access-method-specific options, as <quote>keyword=value</> strings
1655       </entry>
1656      </row>
1657     </tbody>
1658    </tgroup>
1659   </table>
1660  </sect1>
1661
1662  <sect1 id="catalog-pg-constraint">
1663   <title><structname>pg_constraint</structname></title>
1664
1665   <indexterm zone="catalog-pg-constraint">
1666    <primary>pg_constraint</primary>
1667   </indexterm>
1668
1669   <para>
1670    The catalog <structname>pg_constraint</structname> stores check, primary key, unique, and foreign
1671    key constraints on tables.  (Column constraints are not treated
1672    specially.  Every column constraint is equivalent to some table
1673    constraint.)  Not-null constraints are represented in the
1674    <structname>pg_attribute</> catalog.
1675   </para>
1676
1677   <para>
1678    Check constraints on domains are stored here, too.
1679   </para>
1680
1681   <table>
1682    <title><structname>pg_constraint</> Columns</title>
1683
1684    <tgroup cols="4">
1685     <thead>
1686      <row>
1687       <entry>Name</entry>
1688       <entry>Type</entry>
1689       <entry>References</entry>
1690       <entry>Description</entry>
1691      </row>
1692     </thead>
1693
1694     <tbody>
1695      <row>
1696       <entry><structfield>conname</structfield></entry>
1697       <entry><type>name</type></entry>
1698       <entry></entry>
1699       <entry>Constraint name (not necessarily unique!)</entry>
1700      </row>
1701
1702      <row>
1703       <entry><structfield>connamespace</structfield></entry>
1704       <entry><type>oid</type></entry>
1705       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>
1706       <entry>
1707        The OID of the namespace that contains this constraint
1708       </entry>
1709      </row>
1710
1711      <row>
1712       <entry><structfield>contype</structfield></entry>
1713       <entry><type>char</type></entry>
1714       <entry></entry>
1715       <entry>
1716         <literal>c</> = check constraint,
1717         <literal>f</> = foreign key constraint,
1718         <literal>p</> = primary key constraint,
1719         <literal>u</> = unique constraint
1720       </entry>
1721      </row>
1722
1723      <row>
1724       <entry><structfield>condeferrable</structfield></entry>
1725       <entry><type>bool</type></entry>
1726       <entry></entry>
1727       <entry>Is the constraint deferrable?</entry>
1728      </row>
1729
1730      <row>
1731       <entry><structfield>condeferred</structfield></entry>
1732       <entry><type>bool</type></entry>
1733       <entry></entry>
1734       <entry>Is the constraint deferred by default?</entry>
1735      </row>
1736
1737      <row>
1738       <entry><structfield>conrelid</structfield></entry>
1739       <entry><type>oid</type></entry>
1740       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
1741       <entry>The table this constraint is on; 0 if not a table constraint</entry>
1742      </row>
1743
1744      <row>
1745       <entry><structfield>contypid</structfield></entry>
1746       <entry><type>oid</type></entry>
1747       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
1748       <entry>The domain this constraint is on; 0 if not a domain constraint</entry>
1749      </row>
1750
1751      <row>
1752       <entry><structfield>confrelid</structfield></entry>
1753       <entry><type>oid</type></entry>
1754       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
1755       <entry>If a foreign key, the referenced table; else 0</entry>
1756      </row>
1757
1758      <row>
1759       <entry><structfield>confupdtype</structfield></entry>
1760       <entry><type>char</type></entry>
1761       <entry></entry>
1762       <entry>Foreign key update action code:
1763             <literal>a</> = no action,
1764             <literal>r</> = restrict,
1765             <literal>c</> = cascade,
1766             <literal>n</> = set null,
1767             <literal>d</> = set default
1768           </entry>
1769      </row>
1770
1771      <row>
1772       <entry><structfield>confdeltype</structfield></entry>
1773       <entry><type>char</type></entry>
1774       <entry></entry>
1775       <entry>Foreign key deletion action code:
1776             <literal>a</> = no action,
1777             <literal>r</> = restrict,
1778             <literal>c</> = cascade,
1779             <literal>n</> = set null,
1780             <literal>d</> = set default
1781           </entry>
1782      </row>
1783
1784      <row>
1785       <entry><structfield>confmatchtype</structfield></entry>
1786       <entry><type>char</type></entry>
1787       <entry></entry>
1788       <entry>Foreign key match type:
1789             <literal>f</> = full,
1790             <literal>p</> = partial,
1791             <literal>u</> = simple (unspecified)
1792           </entry>
1793      </row>
1794
1795      <row>
1796       <entry><structfield>conislocal</structfield></entry>
1797       <entry><type>bool</type></entry>
1798       <entry></entry>
1799       <entry>
1800        This constraint is defined locally in the relation.  Note that a
1801        constraint can be locally defined and inherited simultaneously
1802       </entry>
1803      </row>
1804
1805      <row>
1806       <entry><structfield>coninhcount</structfield></entry>
1807       <entry><type>int4</type></entry>
1808       <entry></entry>
1809       <entry>
1810        The number of direct ancestors this constraint has.  A constraint with
1811        a nonzero number of ancestors cannot be dropped nor renamed
1812       </entry>
1813      </row>
1814
1815      <row>
1816       <entry><structfield>conkey</structfield></entry>
1817       <entry><type>int2[]</type></entry>
1818       <entry><literal><link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.attnum</></entry>
1819       <entry>If a table constraint (including a foreign key), list of the constrained columns</entry>
1820      </row>
1821
1822      <row>
1823       <entry><structfield>confkey</structfield></entry>
1824       <entry><type>int2[]</type></entry>
1825       <entry><literal><link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.attnum</></entry>
1826       <entry>If a foreign key, list of the referenced columns</entry>
1827      </row>
1828
1829      <row>
1830       <entry><structfield>conpfeqop</structfield></entry>
1831       <entry><type>oid[]</type></entry>
1832       <entry><literal><link linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.oid</></entry>
1833       <entry>If a foreign key, list of the equality operators for PK = FK comparisons</entry>
1834      </row>
1835
1836      <row>
1837       <entry><structfield>conppeqop</structfield></entry>
1838       <entry><type>oid[]</type></entry>
1839       <entry><literal><link linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.oid</></entry>
1840       <entry>If a foreign key, list of the equality operators for PK = PK comparisons</entry>
1841      </row>
1842
1843      <row>
1844       <entry><structfield>conffeqop</structfield></entry>
1845       <entry><type>oid[]</type></entry>
1846       <entry><literal><link linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.oid</></entry>
1847       <entry>If a foreign key, list of the equality operators for FK = FK comparisons</entry>
1848      </row>
1849
1850      <row>
1851       <entry><structfield>conbin</structfield></entry>
1852       <entry><type>text</type></entry>
1853       <entry></entry>
1854       <entry>If a check constraint, an internal representation of the expression</entry>
1855      </row>
1856
1857      <row>
1858       <entry><structfield>consrc</structfield></entry>
1859       <entry><type>text</type></entry>
1860       <entry></entry>
1861       <entry>If a check constraint, a human-readable representation of the expression</entry>
1862      </row>
1863     </tbody>
1864    </tgroup>
1865   </table>
1866
1867   <note>
1868    <para>
1869     <structfield>consrc</structfield> is not updated when referenced objects
1870     change; for example, it won't track renaming of columns.  Rather than
1871     relying on this field, it's best to use <function>pg_get_constraintdef()</>
1872     to extract the definition of a check constraint.
1873    </para>
1874   </note>
1875
1876   <note>
1877    <para>
1878     <literal>pg_class.relchecks</literal> needs to agree with the
1879     number of check-constraint entries found in this table for each
1880     relation.
1881    </para>
1882   </note>
1883
1884  </sect1>
1885
1886  <sect1 id="catalog-pg-conversion">
1887   <title><structname>pg_conversion</structname></title>
1888
1889   <indexterm zone="catalog-pg-conversion">
1890    <primary>pg_conversion</primary>
1891   </indexterm>
1892
1893   <para>
1894    The catalog <structname>pg_conversion</structname> describes the
1895    available encoding conversion procedures.  See
1896    <xref linkend="sql-createconversion" endterm="sql-createconversion-title">
1897    for more information.
1898   </para>
1899
1900   <table>
1901    <title><structname>pg_conversion</> Columns</title>
1902
1903    <tgroup cols="4">
1904     <thead>
1905      <row>
1906       <entry>Name</entry>
1907       <entry>Type</entry>
1908       <entry>References</entry>
1909       <entry>Description</entry>
1910      </row>
1911     </thead>
1912
1913     <tbody>
1914      <row>
1915       <entry><structfield>conname</structfield></entry>
1916       <entry><type>name</type></entry>
1917       <entry></entry>
1918       <entry>Conversion name (unique within a namespace)</entry>
1919      </row>
1920
1921      <row>
1922       <entry><structfield>connamespace</structfield></entry>
1923       <entry><type>oid</type></entry>
1924       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>
1925       <entry>
1926        The OID of the namespace that contains this conversion
1927       </entry>
1928      </row>
1929
1930      <row>
1931       <entry><structfield>conowner</structfield></entry>
1932       <entry><type>oid</type></entry>
1933       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
1934       <entry>Owner of the conversion</entry>
1935      </row>
1936
1937      <row>
1938       <entry><structfield>conforencoding</structfield></entry>
1939       <entry><type>int4</type></entry>
1940       <entry></entry>
1941       <entry>Source encoding ID</entry>
1942      </row>
1943
1944      <row>
1945       <entry><structfield>contoencoding</structfield></entry>
1946       <entry><type>int4</type></entry>
1947       <entry></entry>
1948       <entry>Destination encoding ID</entry>
1949      </row>
1950
1951      <row>
1952       <entry><structfield>conproc</structfield></entry>
1953       <entry><type>regproc</type></entry>
1954       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
1955       <entry>Conversion procedure</entry>
1956      </row>
1957
1958      <row>
1959       <entry><structfield>condefault</structfield></entry>
1960       <entry><type>bool</type></entry>
1961       <entry></entry>
1962       <entry>True if this is the default conversion</entry>
1963      </row>
1964
1965     </tbody>
1966    </tgroup>
1967   </table>
1968
1969  </sect1>
1970
1971  <sect1 id="catalog-pg-database">
1972   <title><structname>pg_database</structname></title>
1973
1974   <indexterm zone="catalog-pg-database">
1975    <primary>pg_database</primary>
1976   </indexterm>
1977
1978   <para>
1979    The catalog <structname>pg_database</structname> stores information about
1980    the available databases.  Databases are created with the <xref
1981    linkend="sql-createdatabase" endterm="sql-createdatabase-title"> command.
1982    Consult <xref linkend="managing-databases"> for details about the meaning
1983    of some of the parameters.
1984   </para>
1985
1986   <para>
1987    Unlike most system catalogs, <structname>pg_database</structname>
1988    is shared across all databases of a cluster: there is only one
1989    copy of <structname>pg_database</structname> per cluster, not
1990    one per database.
1991   </para>
1992
1993   <table>
1994    <title><structname>pg_database</> Columns</title>
1995
1996    <tgroup cols="4">
1997     <thead>
1998      <row>
1999       <entry>Name</entry>
2000       <entry>Type</entry>
2001       <entry>References</entry>
2002       <entry>Description</entry>
2003      </row>
2004     </thead>
2005
2006     <tbody>
2007      <row>
2008       <entry><structfield>datname</structfield></entry>
2009       <entry><type>name</type></entry>
2010       <entry></entry>
2011       <entry>Database name</entry>
2012      </row>
2013
2014      <row>
2015       <entry><structfield>datdba</structfield></entry>
2016       <entry><type>oid</type></entry>
2017       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
2018       <entry>Owner of the database, usually the user who created it</entry>
2019      </row>
2020
2021      <row>
2022       <entry><structfield>encoding</structfield></entry>
2023       <entry><type>int4</type></entry>
2024       <entry></entry>
2025       <entry>Character encoding for this database
2026           (<function>pg_encoding_to_char()</function> can translate
2027            this number to the encoding name)</entry>
2028      </row>
2029
2030      <row>
2031       <entry><structfield>datcollate</structfield></entry>
2032       <entry><type>name</type></entry>
2033       <entry></entry>
2034       <entry>LC_COLLATE for this database</entry>
2035      </row>
2036
2037      <row>
2038       <entry><structfield>datctype</structfield></entry>
2039       <entry><type>name</type></entry>
2040       <entry></entry>
2041       <entry>LC_CTYPE for this database</entry>
2042      </row>
2043
2044      <row>
2045       <entry><structfield>datistemplate</structfield></entry>
2046       <entry><type>bool</type></entry>
2047       <entry></entry>
2048       <entry>
2049        If true then this database can be used in the
2050        <literal>TEMPLATE</literal> clause of <command>CREATE
2051        DATABASE</command> to create a new database as a clone of
2052        this one
2053       </entry>
2054      </row>
2055
2056      <row>
2057       <entry><structfield>datallowconn</structfield></entry>
2058       <entry><type>bool</type></entry>
2059       <entry></entry>
2060       <entry>
2061        If false then no one can connect to this database.  This is
2062        used to protect the <literal>template0</> database from being altered
2063       </entry>
2064      </row>
2065
2066      <row>
2067       <entry><structfield>datconnlimit</structfield></entry>
2068       <entry><type>int4</type></entry>
2069       <entry></entry>
2070       <entry>
2071        Sets maximum number of concurrent connections that can be made
2072        to this database.  -1 means no limit
2073       </entry>
2074      </row>
2075
2076      <row>
2077       <entry><structfield>datlastsysoid</structfield></entry>
2078       <entry><type>oid</type></entry>
2079       <entry></entry>
2080       <entry>
2081        Last system OID in the database; useful
2082        particularly to <application>pg_dump</application>
2083       </entry>
2084      </row>
2085
2086      <row>
2087       <entry><structfield>datfrozenxid</structfield></entry>
2088       <entry><type>xid</type></entry>
2089       <entry></entry>
2090       <entry>
2091        All transaction IDs before this one have been replaced with a permanent
2092        (<quote>frozen</>) transaction ID in this database.  This is used to
2093        track whether the database needs to be vacuumed in order to prevent
2094        transaction ID wraparound or to allow <literal>pg_clog</> to be shrunk.
2095        It is the minimum of the per-table
2096        <structname>pg_class</>.<structfield>relfrozenxid</> values
2097       </entry>
2098      </row>
2099
2100      <row>
2101       <entry><structfield>dattablespace</structfield></entry>
2102       <entry><type>oid</type></entry>
2103       <entry><literal><link linkend="catalog-pg-tablespace"><structname>pg_tablespace</structname></link>.oid</literal></entry>
2104       <entry>
2105        The default tablespace for the database.
2106        Within this database, all tables for which
2107        <structname>pg_class</>.<structfield>reltablespace</> is zero
2108        will be stored in this tablespace; in particular, all the non-shared
2109        system catalogs will be there
2110       </entry>
2111      </row>
2112
2113      <row>
2114       <entry><structfield>datconfig</structfield></entry>
2115       <entry><type>text[]</type></entry>
2116       <entry></entry>
2117       <entry>Session defaults for run-time configuration variables</entry>
2118      </row>
2119
2120      <row>
2121       <entry><structfield>datacl</structfield></entry>
2122       <entry><type>aclitem[]</type></entry>
2123       <entry></entry>
2124       <entry>
2125        Access privileges; see
2126        <xref linkend="sql-grant" endterm="sql-grant-title"> and
2127        <xref linkend="sql-revoke" endterm="sql-revoke-title">
2128        for details
2129       </entry>
2130      </row>
2131     </tbody>
2132    </tgroup>
2133   </table>
2134  </sect1>
2135
2136
2137  <sect1 id="catalog-pg-depend">
2138   <title><structname>pg_depend</structname></title>
2139
2140   <indexterm zone="catalog-pg-depend">
2141    <primary>pg_depend</primary>
2142   </indexterm>
2143
2144   <para>
2145    The catalog <structname>pg_depend</structname> records the dependency
2146    relationships between database objects.  This information allows
2147    <command>DROP</> commands to find which other objects must be dropped
2148    by <command>DROP CASCADE</> or prevent dropping in the <command>DROP
2149    RESTRICT</> case.
2150   </para>
2151
2152   <para>
2153    See also <link linkend="catalog-pg-shdepend"><structname>pg_shdepend</structname></link>,
2154    which performs a similar function for dependencies involving objects
2155    that are shared across a database cluster.
2156   </para>
2157
2158   <table>
2159    <title><structname>pg_depend</> Columns</title>
2160
2161    <tgroup cols="4">
2162     <thead>
2163      <row>
2164       <entry>Name</entry>
2165       <entry>Type</entry>
2166       <entry>References</entry>
2167       <entry>Description</entry>
2168      </row>
2169     </thead>
2170
2171     <tbody>
2172      <row>
2173       <entry><structfield>classid</structfield></entry>
2174       <entry><type>oid</type></entry>
2175       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
2176       <entry>The OID of the system catalog the dependent object is in</entry>
2177      </row>
2178
2179      <row>
2180       <entry><structfield>objid</structfield></entry>
2181       <entry><type>oid</type></entry>
2182       <entry>any OID column</entry>
2183       <entry>The OID of the specific dependent object</entry>
2184      </row>
2185
2186      <row>
2187       <entry><structfield>objsubid</structfield></entry>
2188       <entry><type>int4</type></entry>
2189       <entry></entry>
2190       <entry>
2191        For a table column, this is the column number (the
2192        <structfield>objid</> and <structfield>classid</> refer to the
2193        table itself).  For all other object types, this column is
2194        zero
2195       </entry>
2196      </row>
2197
2198      <row>
2199       <entry><structfield>refclassid</structfield></entry>
2200       <entry><type>oid</type></entry>
2201       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
2202       <entry>The OID of the system catalog the referenced object is in</entry>
2203      </row>
2204
2205      <row>
2206       <entry><structfield>refobjid</structfield></entry>
2207       <entry><type>oid</type></entry>
2208       <entry>any OID column</entry>
2209       <entry>The OID of the specific referenced object</entry>
2210      </row>
2211
2212      <row>
2213       <entry><structfield>refobjsubid</structfield></entry>
2214       <entry><type>int4</type></entry>
2215       <entry></entry>
2216       <entry>
2217        For a table column, this is the column number (the
2218        <structfield>refobjid</> and <structfield>refclassid</> refer
2219        to the table itself).  For all other object types, this column
2220        is zero
2221       </entry>
2222      </row>
2223
2224      <row>
2225       <entry><structfield>deptype</structfield></entry>
2226       <entry><type>char</type></entry>
2227       <entry></entry>
2228       <entry>
2229        A code defining the specific semantics of this dependency relationship; see text
2230       </entry>
2231      </row>
2232
2233     </tbody>
2234    </tgroup>
2235   </table>
2236
2237   <para>
2238    In all cases, a <structname>pg_depend</structname> entry indicates that the
2239    referenced object cannot be dropped without also dropping the dependent
2240    object.  However, there are several subflavors identified by
2241    <structfield>deptype</>:
2242
2243    <variablelist>
2244     <varlistentry>
2245      <term><symbol>DEPENDENCY_NORMAL</> (<literal>n</>)</term>
2246      <listitem>
2247       <para>
2248        A normal relationship between separately-created objects.  The
2249        dependent object can be dropped without affecting the
2250        referenced object.  The referenced object can only be dropped
2251        by specifying <literal>CASCADE</>, in which case the dependent
2252        object is dropped, too.  Example: a table column has a normal
2253        dependency on its data type.
2254       </para>
2255      </listitem>
2256     </varlistentry>
2257
2258     <varlistentry>
2259      <term><symbol>DEPENDENCY_AUTO</> (<literal>a</>)</term>
2260      <listitem>
2261       <para>
2262        The dependent object can be dropped separately from the
2263        referenced object, and should be automatically dropped
2264        (regardless of <literal>RESTRICT</> or <literal>CASCADE</>
2265        mode) if the referenced object is dropped.  Example: a named
2266        constraint on a table is made autodependent on the table, so
2267        that it will go away if the table is dropped.
2268       </para>
2269      </listitem>
2270     </varlistentry>
2271
2272     <varlistentry>
2273      <term><symbol>DEPENDENCY_INTERNAL</> (<literal>i</>)</term>
2274      <listitem>
2275       <para>
2276        The dependent object was created as part of creation of the
2277        referenced object, and is really just a part of its internal
2278        implementation.  A <command>DROP</> of the dependent object
2279        will be disallowed outright (we'll tell the user to issue a
2280        <command>DROP</> against the referenced object, instead).  A
2281        <command>DROP</> of the referenced object will be propagated
2282        through to drop the dependent object whether
2283        <command>CASCADE</> is specified or not.  Example: a trigger
2284        that's created to enforce a foreign-key constraint is made
2285        internally dependent on the constraint's
2286        <structname>pg_constraint</> entry.
2287       </para>
2288      </listitem>
2289     </varlistentry>
2290
2291     <varlistentry>
2292      <term><symbol>DEPENDENCY_PIN</> (<literal>p</>)</term>
2293      <listitem>
2294       <para>
2295        There is no dependent object; this type of entry is a signal
2296        that the system itself depends on the referenced object, and so
2297        that object must never be deleted.  Entries of this type are
2298        created only by <command>initdb</command>.  The columns for the
2299        dependent object contain zeroes.
2300       </para>
2301      </listitem>
2302     </varlistentry>
2303    </variablelist>
2304
2305    Other dependency flavors might be needed in future.
2306   </para>
2307
2308  </sect1>
2309
2310
2311  <sect1 id="catalog-pg-description">
2312   <title><structname>pg_description</structname></title>
2313
2314   <indexterm zone="catalog-pg-description">
2315    <primary>pg_description</primary>
2316   </indexterm>
2317
2318   <para>
2319    The catalog <structname>pg_description</> stores optional descriptions
2320    (comments) for each database object.  Descriptions can be manipulated
2321    with the <xref linkend="sql-comment" endterm="sql-comment-title"> command and viewed with
2322    <application>psql</application>'s <literal>\d</literal> commands.
2323    Descriptions of many built-in system objects are provided in the initial
2324    contents of <structname>pg_description</structname>.
2325   </para>
2326
2327   <para>
2328    See also <link linkend="catalog-pg-shdescription"><structname>pg_shdescription</structname></link>,
2329    which performs a similar function for descriptions involving objects that
2330    are shared across a database cluster.
2331   </para>
2332
2333   <table>
2334    <title><structname>pg_description</> Columns</title>
2335
2336    <tgroup cols="4">
2337     <thead>
2338      <row>
2339       <entry>Name</entry>
2340       <entry>Type</entry>
2341       <entry>References</entry>
2342       <entry>Description</entry>
2343      </row>
2344     </thead>
2345
2346     <tbody>
2347      <row>
2348       <entry><structfield>objoid</structfield></entry>
2349       <entry><type>oid</type></entry>
2350       <entry>any OID column</entry>
2351       <entry>The OID of the object this description pertains to</entry>
2352      </row>
2353
2354      <row>
2355       <entry><structfield>classoid</structfield></entry>
2356       <entry><type>oid</type></entry>
2357       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
2358       <entry>The OID of the system catalog this object appears in</entry>
2359      </row>
2360
2361      <row>
2362       <entry><structfield>objsubid</structfield></entry>
2363       <entry><type>int4</type></entry>
2364       <entry></entry>
2365       <entry>
2366        For a comment on a table column, this is the column number (the
2367        <structfield>objoid</> and <structfield>classoid</> refer to
2368        the table itself).  For all other object types, this column is
2369        zero
2370       </entry>
2371      </row>
2372
2373      <row>
2374       <entry><structfield>description</structfield></entry>
2375       <entry><type>text</type></entry>
2376       <entry></entry>
2377       <entry>Arbitrary text that serves as the description of this object</entry>
2378      </row>
2379     </tbody>
2380    </tgroup>
2381   </table>
2382
2383  </sect1>
2384
2385
2386  <sect1 id="catalog-pg-enum">
2387   <title><structname>pg_enum</structname></title>
2388
2389   <indexterm zone="catalog-pg-enum">
2390    <primary>pg_enum</primary>
2391   </indexterm>
2392
2393   <para>
2394    The <structname>pg_enum</structname> catalog contains entries
2395    matching enum types to their associated values and labels. The
2396    internal representation of a given enum value is actually the OID
2397    of its associated row in <structname>pg_enum</structname>.  The
2398    OIDs for a particular enum type are guaranteed to be ordered in
2399    the way the type should sort, but there is no guarantee about the
2400    ordering of OIDs of unrelated enum types.
2401   </para>
2402
2403   <table>
2404    <title><structname>pg_enum</> Columns</title>
2405
2406    <tgroup cols="4">
2407     <thead>
2408      <row>
2409       <entry>Name</entry>
2410       <entry>Type</entry>
2411       <entry>References</entry>
2412       <entry>Description</entry>
2413      </row>
2414     </thead>
2415
2416     <tbody>
2417      <row>
2418       <entry><structfield>enumtypid</structfield></entry>
2419       <entry><type>oid</type></entry>
2420       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
2421       <entry>The OID of the <structname>pg_type</> entry owning this enum value</entry>
2422      </row>
2423
2424      <row>
2425       <entry><structfield>enumlabel</structfield></entry>
2426       <entry><type>name</type></entry>
2427       <entry></entry>
2428       <entry>The textual label for this enum value</entry>
2429      </row>
2430     </tbody>
2431    </tgroup>
2432   </table>
2433  </sect1>
2434
2435
2436  <sect1 id="catalog-pg-foreign-data-wrapper">
2437   <title><structname>pg_foreign_data_wrapper</structname></title>
2438
2439   <indexterm zone="catalog-pg-foreign-data-wrapper">
2440    <primary>pg_foreign_data_wrapper</primary>
2441   </indexterm>
2442
2443   <para>
2444    The catalog <structname>pg_foreign_data_wrapper</structname> stores
2445    foreign-data wrapper definitions.  A foreign-data wrapper is the
2446    mechanism by which external data, residing on foreign servers, is
2447    accessed.
2448   </para>
2449
2450   <table>
2451    <title><structname>pg_foreign_data_wrapper</> Columns</title>
2452
2453    <tgroup cols="4">
2454     <thead>
2455      <row>
2456       <entry>Name</entry>
2457       <entry>Type</entry>
2458       <entry>References</entry>
2459       <entry>Description</entry>
2460      </row>
2461     </thead>
2462
2463     <tbody>
2464      <row>
2465       <entry><structfield>fdwname</structfield></entry>
2466       <entry><type>name</type></entry>
2467       <entry></entry>
2468       <entry>Name of the foreign-data wrapper</entry>
2469      </row>
2470
2471      <row>
2472       <entry><structfield>fdwowner</structfield></entry>
2473       <entry><type>oid</type></entry>
2474       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
2475       <entry>Owner of the foreign-data wrapper</entry>
2476      </row>
2477
2478      <row>
2479       <entry><structfield>fdwvalidator</structfield></entry>
2480       <entry><type>oid</type></entry>
2481       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
2482       <entry>
2483        References a validator function that is responsible for
2484        checking the validity of the generic options given to the
2485        foreign-data wrapper, as well as to foreign servers and user
2486        mappings using the foreign-data wrapper.  Zero if no validator
2487        is provided.
2488       </entry>
2489      </row>
2490
2491      <row>
2492       <entry><structfield>fdwacl</structfield></entry>
2493       <entry><type>aclitem[]</type></entry>
2494       <entry></entry>
2495       <entry>
2496        Access privileges; see
2497        <xref linkend="sql-grant" endterm="sql-grant-title"> and
2498        <xref linkend="sql-revoke" endterm="sql-revoke-title">
2499        for details
2500       </entry>
2501      </row>
2502
2503      <row>
2504       <entry><structfield>fdwoptions</structfield></entry>
2505       <entry><type>text[]</type></entry>
2506       <entry></entry>
2507       <entry>
2508        Foreign-data wrapper specific options, as <quote>keyword=value</> strings
2509       </entry>
2510      </row>
2511     </tbody>
2512    </tgroup>
2513   </table>
2514  </sect1>
2515
2516
2517  <sect1 id="catalog-pg-foreign-server">
2518   <title><structname>pg_foreign_server</structname></title>
2519
2520   <indexterm zone="catalog-pg-foreign-server">
2521    <primary>pg_foreign_server</primary>
2522   </indexterm>
2523
2524   <para>
2525    The catalog <structname>pg_foreign_server</structname> stores
2526    foreign server definitions.  A foreign server describes the
2527    connection to a remote server, managing external data.  Foreign
2528    servers are accessed via foreign-data wrappers.
2529   </para>
2530
2531   <table>
2532    <title><structname>pg_foreign_server</> Columns</title>
2533
2534    <tgroup cols="4">
2535     <thead>
2536      <row>
2537       <entry>Name</entry>
2538       <entry>Type</entry>
2539       <entry>References</entry>
2540       <entry>Description</entry>
2541      </row>
2542     </thead>
2543
2544     <tbody>
2545      <row>
2546       <entry><structfield>srvname</structfield></entry>
2547       <entry><type>name</type></entry>
2548       <entry></entry>
2549       <entry>Name of the foreign server</entry>
2550      </row>
2551
2552      <row>
2553       <entry><structfield>srvowner</structfield></entry>
2554       <entry><type>oid</type></entry>
2555       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
2556       <entry>Owner of the foreign server</entry>
2557      </row>
2558
2559      <row>
2560       <entry><structfield>srvfdw</structfield></entry>
2561       <entry><type>oid</type></entry>
2562       <entry><literal><link linkend="catalog-pg-foreign-data-wrapper"><structname>pg_foreign_data_wrapper</structname></link>.oid</literal></entry>
2563       <entry>The OID of the foreign-data wrapper of this foreign server</entry>
2564      </row>
2565
2566      <row>
2567       <entry><structfield>srvtype</structfield></entry>
2568       <entry><type>text</type></entry>
2569       <entry></entry>
2570       <entry>Type of the server (optional)</entry>
2571      </row>
2572
2573      <row>
2574       <entry><structfield>srvversion</structfield></entry>
2575       <entry><type>text</type></entry>
2576       <entry></entry>
2577       <entry>Version of the server (optional)</entry>
2578      </row>
2579
2580      <row>
2581       <entry><structfield>srvacl</structfield></entry>
2582       <entry><type>aclitem[]</type></entry>
2583       <entry></entry>
2584       <entry>
2585        Access privileges; see
2586        <xref linkend="sql-grant" endterm="sql-grant-title"> and
2587        <xref linkend="sql-revoke" endterm="sql-revoke-title">
2588        for details
2589       </entry>
2590      </row>
2591
2592      <row>
2593       <entry><structfield>srvoptions</structfield></entry>
2594       <entry><type>text[]</type></entry>
2595       <entry></entry>
2596       <entry>
2597        Foreign server specific options, as <quote>keyword=value</> strings.
2598       </entry>
2599      </row>
2600     </tbody>
2601    </tgroup>
2602   </table>
2603  </sect1>
2604
2605
2606  <sect1 id="catalog-pg-index">
2607   <title><structname>pg_index</structname></title>
2608
2609   <indexterm zone="catalog-pg-index">
2610    <primary>pg_index</primary>
2611   </indexterm>
2612
2613   <para>
2614    The catalog <structname>pg_index</structname> contains part of the information
2615    about indexes.  The rest is mostly in
2616    <structname>pg_class</structname>.
2617   </para>
2618
2619   <table>
2620    <title><structname>pg_index</> Columns</title>
2621
2622    <tgroup cols="4">
2623     <thead>
2624      <row>
2625       <entry>Name</entry>
2626       <entry>Type</entry>
2627       <entry>References</entry>
2628       <entry>Description</entry>
2629      </row>
2630     </thead>
2631
2632     <tbody>
2633      <row>
2634       <entry><structfield>indexrelid</structfield></entry>
2635       <entry><type>oid</type></entry>
2636       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
2637       <entry>The OID of the <structname>pg_class</> entry for this index</entry>
2638      </row>
2639
2640      <row>
2641       <entry><structfield>indrelid</structfield></entry>
2642       <entry><type>oid</type></entry>
2643       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
2644       <entry>The OID of the <structname>pg_class</> entry for the table this index is for</entry>
2645      </row>
2646
2647      <row>
2648       <entry><structfield>indnatts</structfield></entry>
2649       <entry><type>int2</type></entry>
2650       <entry></entry>
2651       <entry>The number of columns in the index (duplicates
2652       <literal>pg_class.relnatts</literal>)</entry>
2653      </row>
2654
2655      <row>
2656       <entry><structfield>indisunique</structfield></entry>
2657       <entry><type>bool</type></entry>
2658       <entry></entry>
2659       <entry>If true, this is a unique index</entry>
2660      </row>
2661
2662      <row>
2663       <entry><structfield>indisprimary</structfield></entry>
2664       <entry><type>bool</type></entry>
2665       <entry></entry>
2666       <entry>If true, this index represents the primary key of the table
2667       (<structfield>indisunique</> should always be true when this is true)</entry>
2668      </row>
2669
2670      <row>
2671       <entry><structfield>indisclustered</structfield></entry>
2672       <entry><type>bool</type></entry>
2673       <entry></entry>
2674       <entry>If true, the table was last clustered on this index</entry>
2675      </row>
2676
2677      <row>
2678       <entry><structfield>indisvalid</structfield></entry>
2679       <entry><type>bool</type></entry>
2680       <entry></entry>
2681       <entry>
2682        If true, the index is currently valid for queries.  False means the
2683        index is possibly incomplete: it must still be modified by
2684        <command>INSERT</>/<command>UPDATE</> operations, but it cannot safely
2685        be used for queries. If it is unique, the uniqueness property is not
2686        true either
2687       </entry>
2688      </row>
2689
2690      <row>
2691       <entry><structfield>indcheckxmin</structfield></entry>
2692       <entry><type>bool</type></entry>
2693       <entry></entry>
2694       <entry>
2695        If true, queries must not use the index until the <structfield>xmin</>
2696        of this <structname>pg_index</> row is below their TransactionXmin
2697        event horizon, because the table may contain broken HOT chains with
2698        incompatible rows that they can see
2699       </entry>
2700      </row>
2701
2702      <row>
2703       <entry><structfield>indisready</structfield></entry>
2704       <entry><type>bool</type></entry>
2705       <entry></entry>
2706       <entry>
2707        If true, the index is currently ready for inserts.  False means the
2708        index must be ignored by <command>INSERT</>/<command>UPDATE</>
2709        operations
2710       </entry>
2711      </row>
2712
2713      <row>
2714       <entry><structfield>indkey</structfield></entry>
2715       <entry><type>int2vector</type></entry>
2716       <entry><literal><link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.attnum</literal></entry>
2717       <entry>
2718        This is an array of <structfield>indnatts</structfield> values that
2719        indicate which table columns this index indexes.  For example a value
2720        of <literal>1 3</literal> would mean that the first and the third table
2721        columns make up the index key.  A zero in this array indicates that the
2722        corresponding index attribute is an expression over the table columns,
2723        rather than a simple column reference
2724       </entry>
2725      </row>
2726
2727      <row>
2728       <entry><structfield>indclass</structfield></entry>
2729       <entry><type>oidvector</type></entry>
2730       <entry><literal><link linkend="catalog-pg-opclass"><structname>pg_opclass</structname></link>.oid</literal></entry>
2731       <entry>
2732        For each column in the index key, this contains the OID of
2733        the operator class to use.  See
2734        <link linkend="catalog-pg-opclass"><structname>pg_opclass</structname></link> for details
2735       </entry>
2736      </row>
2737
2738      <row>
2739       <entry><structfield>indoption</structfield></entry>
2740       <entry><type>int2vector</type></entry>
2741       <entry></entry>
2742       <entry>
2743        This is an array of <structfield>indnatts</structfield> values that
2744        store per-column flag bits.  The meaning of the bits is defined by
2745        the index's access method
2746       </entry>
2747      </row>
2748
2749      <row>
2750       <entry><structfield>indexprs</structfield></entry>
2751       <entry><type>text</type></entry>
2752       <entry></entry>
2753       <entry>Expression trees (in <function>nodeToString()</function> representation)
2754       for index attributes that are not simple column references.  This is a
2755       list with one element for each zero entry in <structfield>indkey</>.
2756       NULL if all index attributes are simple references</entry>
2757      </row>
2758
2759      <row>
2760       <entry><structfield>indpred</structfield></entry>
2761       <entry><type>text</type></entry>
2762       <entry></entry>
2763       <entry>Expression tree (in <function>nodeToString()</function> representation)
2764       for partial index predicate.  NULL if not a partial index</entry>
2765      </row>
2766     </tbody>
2767    </tgroup>
2768   </table>
2769
2770  </sect1>
2771
2772
2773  <sect1 id="catalog-pg-inherits">
2774   <title><structname>pg_inherits</structname></title>
2775
2776   <indexterm zone="catalog-pg-inherits">
2777    <primary>pg_inherits</primary>
2778   </indexterm>
2779
2780   <para>
2781    The catalog <structname>pg_inherits</> records information about
2782    table inheritance hierarchies.  There is one entry for each direct
2783    child table in the database.  (Indirect inheritance can be determined
2784    by following chains of entries.)
2785   </para>
2786
2787   <table>
2788    <title><structname>pg_inherits</> Columns</title>
2789
2790    <tgroup cols="4">
2791     <thead>
2792      <row>
2793       <entry>Name</entry>
2794       <entry>Type</entry>
2795       <entry>References</entry>
2796       <entry>Description</entry>
2797      </row>
2798     </thead>
2799
2800     <tbody>
2801      <row>
2802       <entry><structfield>inhrelid</structfield></entry>
2803       <entry><type>oid</type></entry>
2804       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
2805       <entry>
2806        The OID of the child table
2807       </entry>
2808      </row>
2809
2810      <row>
2811       <entry><structfield>inhparent</structfield></entry>
2812       <entry><type>oid</type></entry>
2813       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
2814       <entry>
2815        The OID of the parent table
2816       </entry>
2817      </row>
2818
2819      <row>
2820       <entry><structfield>inhseqno</structfield></entry>
2821       <entry><type>int4</type></entry>
2822       <entry></entry>
2823       <entry>
2824        If there is more than one direct parent for a child table (multiple
2825        inheritance), this number tells the order in which the
2826        inherited columns are to be arranged.  The count starts at 1
2827       </entry>
2828      </row>
2829     </tbody>
2830    </tgroup>
2831   </table>
2832
2833  </sect1>
2834
2835
2836  <sect1 id="catalog-pg-language">
2837   <title><structname>pg_language</structname></title>
2838
2839   <indexterm zone="catalog-pg-language">
2840    <primary>pg_language</primary>
2841   </indexterm>
2842
2843   <para>
2844    The catalog <structname>pg_language</structname> registers
2845    languages in which you can write functions or stored procedures.
2846    See <xref linkend="sql-createlanguage" endterm="sql-createlanguage-title">
2847    and <xref linkend="xplang"> for more information about language handlers.
2848   </para>
2849
2850   <table>
2851    <title><structname>pg_language</> Columns</title>
2852
2853    <tgroup cols="4">
2854     <thead>
2855      <row>
2856       <entry>Name</entry>
2857       <entry>Type</entry>
2858       <entry>References</entry>
2859       <entry>Description</entry>
2860      </row>
2861     </thead>
2862
2863     <tbody>
2864      <row>
2865       <entry><structfield>lanname</structfield></entry>
2866       <entry><type>name</type></entry>
2867       <entry></entry>
2868       <entry>Name of the language</entry>
2869      </row>
2870
2871      <row>
2872       <entry><structfield>lanowner</structfield></entry>
2873       <entry><type>oid</type></entry>
2874       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
2875       <entry>Owner of the language</entry>
2876      </row>
2877
2878      <row>
2879       <entry><structfield>lanispl</structfield></entry>
2880       <entry><type>bool</type></entry>
2881       <entry></entry>
2882       <entry>
2883        This is false for internal languages (such as
2884        <acronym>SQL</acronym>) and true for user-defined languages.
2885        Currently, <application>pg_dump</application> still uses this
2886        to determine which languages need to be dumped, but this might be
2887        replaced by a different mechanism in the future
2888       </entry>
2889      </row>
2890
2891      <row>
2892       <entry><structfield>lanpltrusted</structfield></entry>
2893       <entry><type>bool</type></entry>
2894       <entry></entry>
2895       <entry>
2896        True if this is a trusted language, which means that it is believed
2897        not to grant access to anything outside the normal SQL execution
2898        environment.  Only superusers can create functions in untrusted
2899        languages
2900       </entry>
2901      </row>
2902
2903      <row>
2904       <entry><structfield>lanplcallfoid</structfield></entry>
2905       <entry><type>oid</type></entry>
2906       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
2907       <entry>
2908        For noninternal languages this references the language
2909        handler, which is a special function that is responsible for
2910        executing all functions that are written in the particular
2911        language
2912       </entry>
2913      </row>
2914
2915      <row>
2916       <entry><structfield>lanvalidator</structfield></entry>
2917       <entry><type>oid</type></entry>
2918       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
2919       <entry>
2920        This references a language validator function that is responsible
2921        for checking the syntax and validity of new functions when they
2922        are created.  Zero if no validator is provided
2923       </entry>
2924      </row>
2925
2926      <row>
2927       <entry><structfield>lanacl</structfield></entry>
2928       <entry><type>aclitem[]</type></entry>
2929       <entry></entry>
2930       <entry>
2931        Access privileges; see
2932        <xref linkend="sql-grant" endterm="sql-grant-title"> and
2933        <xref linkend="sql-revoke" endterm="sql-revoke-title">
2934        for details
2935       </entry>
2936      </row>
2937     </tbody>
2938    </tgroup>
2939   </table>
2940
2941  </sect1>
2942
2943
2944  <sect1 id="catalog-pg-largeobject">
2945   <title><structname>pg_largeobject</structname></title>
2946
2947   <indexterm zone="catalog-pg-largeobject">
2948    <primary>pg_largeobject</primary>
2949   </indexterm>
2950
2951   <para>
2952    The catalog <structname>pg_largeobject</structname> holds the data making up
2953    <quote>large objects</quote>.  A large object is identified by an
2954    OID assigned when it is created.  Each large object is broken into
2955    segments or <quote>pages</> small enough to be conveniently stored as rows
2956    in <structname>pg_largeobject</structname>.
2957    The amount of data per page is defined to be <symbol>LOBLKSIZE</> (which is currently
2958    <literal>BLCKSZ/4</>, or typically 2 kB).
2959   </para>
2960
2961   <table>
2962    <title><structname>pg_largeobject</> Columns</title>
2963
2964    <tgroup cols="3">
2965     <thead>
2966      <row>
2967       <entry>Name</entry>
2968       <entry>Type</entry>
2969       <entry>Description</entry>
2970      </row>
2971     </thead>
2972
2973     <tbody>
2974      <row>
2975       <entry><structfield>loid</structfield></entry>
2976       <entry><type>oid</type></entry>
2977       <entry>Identifier of the large object that includes this page</entry>
2978      </row>
2979
2980      <row>
2981       <entry><structfield>pageno</structfield></entry>
2982       <entry><type>int4</type></entry>
2983       <entry>Page number of this page within its large object
2984       (counting from zero)</entry>
2985      </row>
2986
2987      <row>
2988       <entry><structfield>data</structfield></entry>
2989       <entry><type>bytea</type></entry>
2990       <entry>
2991        Actual data stored in the large object.
2992        This will never be more than <symbol>LOBLKSIZE</> bytes and might be less
2993       </entry>
2994      </row>
2995     </tbody>
2996    </tgroup>
2997   </table>
2998
2999   <para>
3000    Each row of <structname>pg_largeobject</structname> holds data
3001    for one page of a large object, beginning at
3002    byte offset (<literal>pageno * LOBLKSIZE</>) within the object.  The implementation
3003    allows sparse storage: pages might be missing, and might be shorter than
3004    <literal>LOBLKSIZE</> bytes even if they are not the last page of the object.
3005    Missing regions within a large object read as zeroes.
3006   </para>
3007
3008  </sect1>
3009
3010
3011  <sect1 id="catalog-pg-listener">
3012   <title><structname>pg_listener</structname></title>
3013
3014   <indexterm zone="catalog-pg-listener">
3015    <primary>pg_listener</primary>
3016   </indexterm>
3017
3018   <para>
3019    The catalog <structname>pg_listener</structname> supports the
3020    <xref linkend="sql-listen" endterm="sql-listen-title"> and
3021    <xref linkend="sql-notify" endterm="sql-notify-title">
3022    commands.  A listener creates an entry in
3023    <structname>pg_listener</structname> for each notification name
3024    it is listening for.  A notifier scans <structname>pg_listener</structname>
3025    and updates each matching entry to show that a notification has occurred.
3026    The notifier also sends a signal (using the PID recorded in the table)
3027    to awaken the listener from sleep.
3028   </para>
3029
3030   <table>
3031    <title><structname>pg_listener</> Columns</title>
3032
3033    <tgroup cols="3">
3034     <thead>
3035      <row>
3036       <entry>Name</entry>
3037       <entry>Type</entry>
3038       <entry>Description</entry>
3039      </row>
3040     </thead>
3041
3042     <tbody>
3043      <row>
3044       <entry><structfield>relname</structfield></entry>
3045       <entry><type>name</type></entry>
3046       <entry>
3047        Notify condition name.  (The name need not match any actual
3048        relation in the database; the name <structfield>relname</> is historical.)
3049       </entry>
3050      </row>
3051
3052      <row>
3053       <entry><structfield>listenerpid</structfield></entry>
3054       <entry><type>int4</type></entry>
3055       <entry>PID of the server process that created this entry</entry>
3056      </row>
3057
3058      <row>
3059       <entry><structfield>notification</structfield></entry>
3060       <entry><type>int4</type></entry>
3061       <entry>
3062        Zero if no event is pending for this listener.  If an event is
3063        pending, the PID of the server process that sent the notification
3064       </entry>
3065      </row>
3066     </tbody>
3067    </tgroup>
3068   </table>
3069
3070  </sect1>
3071
3072
3073  <sect1 id="catalog-pg-namespace">
3074   <title><structname>pg_namespace</structname></title>
3075
3076   <indexterm zone="catalog-pg-namespace">
3077    <primary>pg_namespace</primary>
3078   </indexterm>
3079
3080   <para>
3081    The catalog <structname>pg_namespace</> stores namespaces.
3082    A namespace is the structure underlying SQL schemas: each namespace
3083    can have a separate collection of relations, types, etc. without name
3084    conflicts.
3085   </para>
3086
3087   <table>
3088    <title><structname>pg_namespace</> Columns</title>
3089
3090    <tgroup cols="4">
3091     <thead>
3092      <row>
3093       <entry>Name</entry>
3094       <entry>Type</entry>
3095       <entry>References</entry>
3096       <entry>Description</entry>
3097      </row>
3098     </thead>
3099
3100     <tbody>
3101      <row>
3102       <entry><structfield>nspname</structfield></entry>
3103       <entry><type>name</type></entry>
3104       <entry></entry>
3105       <entry>Name of the namespace</entry>
3106      </row>
3107
3108      <row>
3109       <entry><structfield>nspowner</structfield></entry>
3110       <entry><type>oid</type></entry>
3111       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
3112       <entry>Owner of the namespace</entry>
3113      </row>
3114
3115      <row>
3116       <entry><structfield>nspacl</structfield></entry>
3117       <entry><type>aclitem[]</type></entry>
3118       <entry></entry>
3119       <entry>
3120        Access privileges; see
3121        <xref linkend="sql-grant" endterm="sql-grant-title"> and
3122        <xref linkend="sql-revoke" endterm="sql-revoke-title">
3123        for details
3124       </entry>
3125      </row>
3126     </tbody>
3127    </tgroup>
3128   </table>
3129
3130  </sect1>
3131
3132
3133  <sect1 id="catalog-pg-opclass">
3134   <title><structname>pg_opclass</structname></title>
3135
3136   <indexterm zone="catalog-pg-opclass">
3137    <primary>pg_opclass</primary>
3138   </indexterm>
3139
3140   <para>
3141    The catalog <structname>pg_opclass</structname> defines
3142    index access method operator classes.  Each operator class defines
3143    semantics for index columns of a particular data type and a particular
3144    index access method.  An operator class essentially specifies that a
3145    particular operator family is applicable to a particular indexable column
3146    data type.  The set of operators from the family that are actually usable
3147    with the indexed column are whichever ones accept the column's data type
3148    as their lefthand input.
3149   </para>
3150
3151   <para>
3152    Operator classes are described at length in <xref linkend="xindex">.
3153   </para>
3154
3155   <table>
3156    <title><structname>pg_opclass</> Columns</title>
3157
3158    <tgroup cols="4">
3159     <thead>
3160      <row>
3161       <entry>Name</entry>
3162       <entry>Type</entry>
3163       <entry>References</entry>
3164       <entry>Description</entry>
3165      </row>
3166     </thead>
3167     <tbody>
3168
3169      <row>
3170       <entry><structfield>opcmethod</structfield></entry>
3171       <entry><type>oid</type></entry>
3172       <entry><literal><link linkend="catalog-pg-am"><structname>pg_am</structname></link>.oid</literal></entry>
3173       <entry>Index access method operator class is for</entry>
3174      </row>
3175
3176      <row>
3177       <entry><structfield>opcname</structfield></entry>
3178       <entry><type>name</type></entry>
3179       <entry></entry>
3180       <entry>Name of this operator class</entry>
3181      </row>
3182
3183      <row>
3184       <entry><structfield>opcnamespace</structfield></entry>
3185       <entry><type>oid</type></entry>
3186       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>
3187       <entry>Namespace of this operator class</entry>
3188      </row>
3189
3190      <row>
3191       <entry><structfield>opcowner</structfield></entry>
3192       <entry><type>oid</type></entry>
3193       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
3194       <entry>Owner of the operator class</entry>
3195      </row>
3196
3197      <row>
3198       <entry><structfield>opcfamily</structfield></entry>
3199       <entry><type>oid</type></entry>
3200       <entry><literal><link linkend="catalog-pg-opfamily"><structname>pg_opfamily</structname></link>.oid</literal></entry>
3201       <entry>Operator family containing the operator class</entry>
3202      </row>
3203
3204      <row>
3205       <entry><structfield>opcintype</structfield></entry>
3206       <entry><type>oid</type></entry>
3207       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
3208       <entry>Data type that the operator class indexes</entry>
3209      </row>
3210
3211      <row>
3212       <entry><structfield>opcdefault</structfield></entry>
3213       <entry><type>bool</type></entry>
3214       <entry></entry>
3215       <entry>True if this operator class is the default for <structfield>opcintype</></entry>
3216      </row>
3217
3218      <row>
3219       <entry><structfield>opckeytype</structfield></entry>
3220       <entry><type>oid</type></entry>
3221       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
3222       <entry>Type of data stored in index, or zero if same as <structfield>opcintype</></entry>
3223      </row>
3224
3225     </tbody>
3226    </tgroup>
3227   </table>
3228
3229   <para>
3230    An operator class's <structfield>opcmethod</> must match the
3231    <structname>opfmethod</> of its containing operator family.
3232    Also, there must be no more than one <structname>pg_opclass</structname>
3233    row having <structname>opcdefault</> true for any given combination of
3234    <structname>opcmethod</> and <structname>opcintype</>.
3235   </para>
3236
3237  </sect1>
3238
3239
3240  <sect1 id="catalog-pg-operator">
3241   <title><structname>pg_operator</structname></title>
3242
3243   <indexterm zone="catalog-pg-operator">
3244    <primary>pg_operator</primary>
3245   </indexterm>
3246
3247   <para>
3248    The catalog <structname>pg_operator</> stores information about operators.
3249    See <xref linkend="sql-createoperator" endterm="sql-createoperator-title">
3250    and <xref linkend="xoper"> for more information.
3251   </para>
3252
3253   <table>
3254    <title><structname>pg_operator</> Columns</title>
3255
3256    <tgroup cols="4">
3257     <thead>
3258      <row>
3259       <entry>Name</entry>
3260       <entry>Type</entry>
3261       <entry>References</entry>
3262       <entry>Description</entry>
3263      </row>
3264     </thead>
3265
3266     <tbody>
3267      <row>
3268       <entry><structfield>oprname</structfield></entry>
3269       <entry><type>name</type></entry>
3270       <entry></entry>
3271       <entry>Name of the operator</entry>
3272      </row>
3273
3274      <row>
3275       <entry><structfield>oprnamespace</structfield></entry>
3276       <entry><type>oid</type></entry>
3277       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>
3278       <entry>
3279        The OID of the namespace that contains this operator
3280       </entry>
3281      </row>
3282
3283      <row>
3284       <entry><structfield>oprowner</structfield></entry>
3285       <entry><type>oid</type></entry>
3286       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
3287       <entry>Owner of the operator</entry>
3288      </row>
3289
3290      <row>
3291       <entry><structfield>oprkind</structfield></entry>
3292       <entry><type>char</type></entry>
3293       <entry></entry>
3294       <entry>
3295        <literal>b</> = infix (<quote>both</quote>), <literal>l</> = prefix
3296        (<quote>left</quote>), <literal>r</> = postfix (<quote>right</quote>)
3297       </entry>
3298      </row>
3299
3300      <row>
3301       <entry><structfield>oprcanmerge</structfield></entry>
3302       <entry><type>bool</type></entry>
3303       <entry></entry>
3304       <entry>This operator supports merge joins</entry>
3305      </row>
3306
3307      <row>
3308       <entry><structfield>oprcanhash</structfield></entry>
3309       <entry><type>bool</type></entry>
3310       <entry></entry>
3311       <entry>This operator supports hash joins</entry>
3312      </row>
3313
3314      <row>
3315       <entry><structfield>oprleft</structfield></entry>
3316       <entry><type>oid</type></entry>
3317       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
3318       <entry>Type of the left operand</entry>
3319      </row>
3320
3321      <row>
3322       <entry><structfield>oprright</structfield></entry>
3323       <entry><type>oid</type></entry>
3324       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
3325       <entry>Type of the right operand</entry>
3326      </row>
3327
3328      <row>
3329       <entry><structfield>oprresult</structfield></entry>
3330       <entry><type>oid</type></entry>
3331       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
3332       <entry>Type of the result</entry>
3333      </row>
3334
3335      <row>
3336       <entry><structfield>oprcom</structfield></entry>
3337       <entry><type>oid</type></entry>
3338       <entry><literal><link linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.oid</literal></entry>
3339       <entry>Commutator of this operator, if any</entry>
3340      </row>
3341
3342      <row>
3343       <entry><structfield>oprnegate</structfield></entry>
3344       <entry><type>oid</type></entry>
3345       <entry><literal><link linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.oid</literal></entry>
3346       <entry>Negator of this operator, if any</entry>
3347      </row>
3348
3349      <row>
3350       <entry><structfield>oprcode</structfield></entry>
3351       <entry><type>regproc</type></entry>
3352       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
3353       <entry>Function that implements this operator</entry>
3354      </row>
3355
3356      <row>
3357       <entry><structfield>oprrest</structfield></entry>
3358       <entry><type>regproc</type></entry>
3359       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
3360       <entry>Restriction selectivity estimation function for this operator</entry>
3361      </row>
3362
3363      <row>
3364       <entry><structfield>oprjoin</structfield></entry>
3365       <entry><type>regproc</type></entry>
3366       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
3367       <entry>Join selectivity estimation function for this operator</entry>
3368      </row>
3369     </tbody>
3370    </tgroup>
3371   </table>
3372
3373   <para>
3374    Unused column contain zeroes. For example, <structfield>oprleft</structfield>
3375    is zero for a prefix operator.
3376   </para>
3377
3378  </sect1>
3379
3380
3381  <sect1 id="catalog-pg-opfamily">
3382   <title><structname>pg_opfamily</structname></title>
3383
3384   <indexterm zone="catalog-pg-opfamily">
3385    <primary>pg_opfamily</primary>
3386   </indexterm>
3387
3388   <para>
3389    The catalog <structname>pg_opfamily</structname> defines operator families.
3390    Each operator family is a collection of operators and associated
3391    support routines that implement the semantics specified for a particular
3392    index access method.  Furthermore, the operators in a family are all
3393    <quote>compatible</>, in a way that is specified by the access method.
3394    The operator family concept allows cross-data-type operators to be used
3395    with indexes and to be reasoned about using knowledge of access method
3396    semantics.
3397   </para>
3398
3399   <para>
3400    Operator families are described at length in <xref linkend="xindex">.
3401   </para>
3402
3403   <table>
3404    <title><structname>pg_opfamily</> Columns</title>
3405
3406    <tgroup cols="4">
3407     <thead>
3408      <row>
3409       <entry>Name</entry>
3410       <entry>Type</entry>
3411       <entry>References</entry>
3412       <entry>Description</entry>
3413      </row>
3414     </thead>
3415     <tbody>
3416
3417      <row>
3418       <entry><structfield>opfmethod</structfield></entry>
3419       <entry><type>oid</type></entry>
3420       <entry><literal><link linkend="catalog-pg-am"><structname>pg_am</structname></link>.oid</literal></entry>
3421       <entry>Index access method operator family is for</entry>
3422      </row>
3423
3424      <row>
3425       <entry><structfield>opfname</structfield></entry>
3426       <entry><type>name</type></entry>
3427       <entry></entry>
3428       <entry>Name of this operator family</entry>
3429      </row>
3430
3431      <row>
3432       <entry><structfield>opfnamespace</structfield></entry>
3433       <entry><type>oid</type></entry>
3434       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>
3435       <entry>Namespace of this operator family</entry>
3436      </row>
3437
3438      <row>
3439       <entry><structfield>opfowner</structfield></entry>
3440       <entry><type>oid</type></entry>
3441       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
3442       <entry>Owner of the operator family</entry>
3443      </row>
3444
3445     </tbody>
3446    </tgroup>
3447   </table>
3448
3449   <para>
3450    The majority of the information defining an operator family is not in its
3451    <structname>pg_opfamily</structname> row, but in the associated rows in
3452    <link linkend="catalog-pg-amop"><structname>pg_amop</structname></link>,
3453    <link linkend="catalog-pg-amproc"><structname>pg_amproc</structname></link>,
3454    and
3455    <link linkend="catalog-pg-opclass"><structname>pg_opclass</structname></link>.
3456   </para>
3457
3458  </sect1>
3459
3460
3461  <sect1 id="catalog-pg-pltemplate">
3462   <title><structname>pg_pltemplate</structname></title>
3463
3464   <indexterm zone="catalog-pg-pltemplate">
3465    <primary>pg_pltemplate</primary>
3466   </indexterm>
3467
3468   <para>
3469    The catalog <structname>pg_pltemplate</structname> stores
3470    <quote>template</> information for procedural languages.
3471    A template for a language allows the language to be created in a
3472    particular database by a simple <command>CREATE LANGUAGE</> command,
3473    with no need to specify implementation details.
3474   </para>
3475
3476   <para>
3477    Unlike most system catalogs, <structname>pg_pltemplate</structname>
3478    is shared across all databases of a cluster: there is only one
3479    copy of <structname>pg_pltemplate</structname> per cluster, not
3480    one per database.  This allows the information to be accessible in
3481    each database as it is needed.
3482   </para>
3483
3484   <table>
3485    <title><structname>pg_pltemplate</> Columns</title>
3486
3487    <tgroup cols="3">
3488     <thead>
3489      <row>
3490       <entry>Name</entry>
3491       <entry>Type</entry>
3492       <entry>Description</entry>
3493      </row>
3494     </thead>
3495
3496     <tbody>
3497      <row>
3498       <entry><structfield>tmplname</structfield></entry>
3499       <entry><type>name</type></entry>
3500       <entry>Name of the language this template is for</entry>
3501      </row>
3502
3503      <row>
3504       <entry><structfield>tmpltrusted</structfield></entry>
3505       <entry><type>boolean</type></entry>
3506       <entry>True if language is considered trusted</entry>
3507      </row>
3508
3509      <row>
3510       <entry><structfield>tmpldbacreate</structfield></entry>
3511       <entry><type>boolean</type></entry>
3512       <entry>True if language may be created by a database owner</entry>
3513      </row>
3514
3515      <row>
3516       <entry><structfield>tmplhandler</structfield></entry>
3517       <entry><type>text</type></entry>
3518       <entry>Name of call handler function</entry>
3519      </row>
3520
3521      <row>
3522       <entry><structfield>tmplvalidator</structfield></entry>
3523       <entry><type>text</type></entry>
3524       <entry>Name of validator function, or NULL if none</entry>
3525      </row>
3526
3527      <row>
3528       <entry><structfield>tmpllibrary</structfield></entry>
3529       <entry><type>text</type></entry>
3530       <entry>Path of shared library that implements language</entry>
3531      </row>
3532
3533      <row>
3534       <entry><structfield>tmplacl</structfield></entry>
3535       <entry><type>aclitem[]</type></entry>
3536       <entry>Access privileges for template (not yet used)</entry>
3537      </row>
3538
3539     </tbody>
3540    </tgroup>
3541   </table>
3542
3543   <para>
3544    There are not currently any commands that manipulate procedural language
3545    templates; to change the built-in information, a superuser must modify
3546    the table using ordinary <command>INSERT</command>, <command>DELETE</command>,
3547    or <command>UPDATE</command> commands.  It is likely that a future
3548    release of <productname>PostgreSQL</productname> will offer
3549    commands to change the entries in a cleaner fashion.
3550   </para>
3551
3552   <para>
3553    When implemented, the <structfield>tmplacl</structfield> field will provide
3554    access control for the template itself (i.e., the right to create a
3555    language using it), not for the languages created from the template.
3556   </para>
3557
3558  </sect1>
3559
3560
3561  <sect1 id="catalog-pg-proc">
3562   <title><structname>pg_proc</structname></title>
3563
3564   <indexterm zone="catalog-pg-proc">
3565    <primary>pg_proc</primary>
3566   </indexterm>
3567
3568   <para>
3569    The catalog <structname>pg_proc</> stores information about functions (or procedures).
3570    See <xref linkend="sql-createfunction" endterm="sql-createfunction-title">
3571    and <xref linkend="xfunc"> for more information.
3572   </para>
3573
3574   <para>
3575    The table contains data for aggregate functions as well as plain functions.
3576    If <structfield>proisagg</structfield> is true, there should be a matching
3577    row in <structfield>pg_aggregate</structfield>.
3578   </para>
3579
3580   <table>
3581    <title><structname>pg_proc</> Columns</title>
3582
3583    <tgroup cols="4">
3584     <thead>
3585      <row>
3586       <entry>Name</entry>
3587       <entry>Type</entry>
3588       <entry>References</entry>
3589       <entry>Description</entry>
3590      </row>
3591     </thead>
3592
3593     <tbody>
3594      <row>
3595       <entry><structfield>proname</structfield></entry>
3596       <entry><type>name</type></entry>
3597       <entry></entry>
3598       <entry>Name of the function</entry>
3599      </row>
3600
3601      <row>
3602       <entry><structfield>pronamespace</structfield></entry>
3603       <entry><type>oid</type></entry>
3604       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>
3605       <entry>
3606        The OID of the namespace that contains this function
3607       </entry>
3608      </row>
3609
3610      <row>
3611       <entry><structfield>proowner</structfield></entry>
3612       <entry><type>oid</type></entry>
3613       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
3614       <entry>Owner of the function</entry>
3615      </row>
3616
3617      <row>
3618       <entry><structfield>prolang</structfield></entry>
3619       <entry><type>oid</type></entry>
3620       <entry><literal><link linkend="catalog-pg-language"><structname>pg_language</structname></link>.oid</literal></entry>
3621       <entry>Implementation language or call interface of this function</entry>
3622      </row>
3623
3624      <row>
3625       <entry><structfield>procost</structfield></entry>
3626       <entry><type>float4</type></entry>
3627       <entry></entry>
3628       <entry>Estimated execution cost (in units of
3629        <xref linkend="guc-cpu-operator-cost">); if <structfield>proretset</>,
3630        this is cost per row returned</entry>
3631      </row>
3632
3633      <row>
3634       <entry><structfield>prorows</structfield></entry>
3635       <entry><type>float4</type></entry>
3636       <entry></entry>
3637       <entry>Estimated number of result rows (zero if not <structfield>proretset</>)</entry>
3638      </row>
3639
3640      <row>
3641       <entry><structfield>provariadic</structfield></entry>
3642       <entry><type>oid</type></entry>
3643       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
3644       <entry>Data type of the variadic array parameter's elements,
3645        or zero if the function does not have a variadic parameter</entry>
3646      </row>
3647
3648      <row>
3649       <entry><structfield>proisagg</structfield></entry>
3650       <entry><type>bool</type></entry>
3651       <entry></entry>
3652       <entry>Function is an aggregate function</entry>
3653      </row>
3654
3655      <row>
3656       <entry><structfield>proiswindow</structfield></entry>
3657       <entry><type>bool</type></entry>
3658       <entry></entry>
3659       <entry>Function is a window function</entry>
3660      </row>
3661
3662      <row>
3663       <entry><structfield>prosecdef</structfield></entry>
3664       <entry><type>bool</type></entry>
3665       <entry></entry>
3666       <entry>Function is a security definer (i.e., a <quote>setuid</>
3667       function)</entry>
3668      </row>
3669
3670      <row>
3671       <entry><structfield>proisstrict</structfield></entry>
3672       <entry><type>bool</type></entry>
3673       <entry></entry>
3674       <entry>
3675        Function returns null if any call argument is null.  In that
3676        case the function won't actually be called at all.  Functions
3677        that are not <quote>strict</quote> must be prepared to handle
3678        null inputs
3679       </entry>
3680      </row>
3681
3682      <row>
3683       <entry><structfield>proretset</structfield></entry>
3684       <entry><type>bool</type></entry>
3685       <entry></entry>
3686       <entry>Function returns a set (i.e., multiple values of the specified
3687       data type)</entry>
3688      </row>
3689
3690      <row>
3691       <entry><structfield>provolatile</structfield></entry>
3692       <entry><type>char</type></entry>
3693       <entry></entry>
3694       <entry>
3695        <structfield>provolatile</structfield> tells whether the function's
3696        result depends only on its input arguments, or is affected by outside
3697        factors.
3698        It is <literal>i</literal> for <quote>immutable</> functions,
3699        which always deliver the same result for the same inputs.
3700        It is <literal>s</literal> for <quote>stable</> functions,
3701        whose results (for fixed inputs) do not change within a scan.
3702        It is <literal>v</literal> for <quote>volatile</> functions,
3703        whose results might change at any time.  (Use <literal>v</literal> also
3704        for functions with side-effects, so that calls to them cannot get
3705        optimized away.)
3706       </entry>
3707      </row>
3708
3709      <row>
3710       <entry><structfield>pronargs</structfield></entry>
3711       <entry><type>int2</type></entry>
3712       <entry></entry>
3713       <entry>Number of input arguments</entry>
3714      </row>
3715
3716      <row>
3717       <entry><structfield>pronargdefaults</structfield></entry>
3718       <entry><type>int2</type></entry>
3719       <entry></entry>
3720       <entry>Number of arguments that have defaults</entry>
3721      </row>
3722
3723      <row>
3724       <entry><structfield>prorettype</structfield></entry>
3725       <entry><type>oid</type></entry>
3726       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
3727       <entry>Data type of the return value</entry>
3728      </row>
3729
3730      <row>
3731       <entry><structfield>proargtypes</structfield></entry>
3732       <entry><type>oidvector</type></entry>
3733       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
3734       <entry>
3735        An array with the data types of the function arguments.  This includes
3736        only input arguments (including <literal>INOUT</literal> and
3737        <literal>VARIADIC</> arguments), and thus represents
3738        the call signature of the function
3739       </entry>
3740      </row>
3741
3742      <row>
3743       <entry><structfield>proallargtypes</structfield></entry>
3744       <entry><type>oid[]</type></entry>
3745       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
3746       <entry>
3747        An array with the data types of the function arguments.  This includes
3748        all arguments (including <literal>OUT</literal> and
3749        <literal>INOUT</literal> arguments); however, if all the
3750        arguments are <literal>IN</literal> arguments, this field will be null.
3751        Note that subscripting is 1-based, whereas for historical reasons
3752        <structfield>proargtypes</> is subscripted from 0
3753       </entry>
3754      </row>
3755
3756      <row>
3757       <entry><structfield>proargmodes</structfield></entry>
3758       <entry><type>char[]</type></entry>
3759       <entry></entry>
3760       <entry>
3761         An array with the modes of the function arguments, encoded as
3762         <literal>i</literal> for <literal>IN</> arguments,
3763         <literal>o</literal> for <literal>OUT</> arguments,
3764         <literal>b</literal> for <literal>INOUT</> arguments,
3765         <literal>v</literal> for <literal>VARIADIC</> arguments,
3766         <literal>t</literal> for <literal>TABLE</> arguments.
3767         If all the arguments are <literal>IN</literal> arguments,
3768         this field will be null.
3769         Note that subscripts correspond to positions of
3770         <structfield>proallargtypes</> not <structfield>proargtypes</>
3771       </entry>
3772      </row>
3773
3774      <row>
3775       <entry><structfield>proargnames</structfield></entry>
3776       <entry><type>text[]</type></entry>
3777       <entry></entry>
3778       <entry>
3779         An array with the names of the function arguments.
3780         Arguments without a name are set to empty strings in the array.
3781         If none of the arguments have a name, this field will be null.
3782         Note that subscripts correspond to positions of
3783         <structfield>proallargtypes</> not <structfield>proargtypes</>
3784       </entry>
3785      </row>
3786
3787      <row>
3788       <entry><structfield>proargdefaults</structfield></entry>
3789       <entry><type>text</type></entry>
3790       <entry></entry>
3791       <entry>
3792        Expression trees (in <function>nodeToString()</function> representation)
3793        for default values.  This is a list with
3794        <structfield>pronargdefaults</> elements, corresponding to the last
3795        <replaceable>N</> <emphasis>input</> arguments (i.e., the last
3796        <replaceable>N</> <structfield>proargtypes</> positions).
3797        If none of the arguments have defaults, this field will be null
3798       </entry>
3799      </row>
3800
3801      <row>
3802       <entry><structfield>prosrc</structfield></entry>
3803       <entry><type>text</type></entry>
3804       <entry></entry>
3805       <entry>
3806        This tells the function handler how to invoke the function.  It
3807        might be the actual source code of the function for interpreted
3808        languages, a link symbol, a file name, or just about anything
3809        else, depending on the implementation language/call convention
3810       </entry>
3811      </row>
3812
3813      <row>
3814       <entry><structfield>probin</structfield></entry>
3815       <entry><type>bytea</type></entry>
3816       <entry></entry>
3817       <entry>
3818        Additional information about how to invoke the function.
3819        Again, the interpretation is language-specific
3820       </entry>
3821      </row>
3822
3823      <row>
3824       <entry><structfield>proconfig</structfield></entry>
3825       <entry><type>text[]</type></entry>
3826       <entry></entry>
3827       <entry>Function's local settings for run-time configuration variables</entry>
3828      </row>
3829
3830      <row>
3831       <entry><structfield>proacl</structfield></entry>
3832       <entry><type>aclitem[]</type></entry>
3833       <entry></entry>
3834       <entry>
3835        Access privileges; see
3836        <xref linkend="sql-grant" endterm="sql-grant-title"> and
3837        <xref linkend="sql-revoke" endterm="sql-revoke-title">
3838        for details
3839       </entry>
3840      </row>
3841     </tbody>
3842    </tgroup>
3843   </table>
3844
3845   <para>
3846    For compiled functions, both built-in and dynamically loaded,
3847    <structfield>prosrc</structfield> contains the function's C-language
3848    name (link symbol).  For all other currently-known language types,
3849    <structfield>prosrc</structfield> contains the function's source
3850    text.  <structfield>probin</structfield> is unused except for
3851    dynamically-loaded C functions, for which it gives the name of the
3852    shared library file containing the function.
3853   </para>
3854
3855  </sect1>
3856
3857  <sect1 id="catalog-pg-rewrite">
3858   <title><structname>pg_rewrite</structname></title>
3859
3860   <indexterm zone="catalog-pg-rewrite">
3861    <primary>pg_rewrite</primary>
3862   </indexterm>
3863
3864   <para>
3865    The catalog <structname>pg_rewrite</structname> stores rewrite rules for tables and views.
3866   </para>
3867
3868   <table>
3869    <title><structname>pg_rewrite</> Columns</title>
3870
3871    <tgroup cols="4">
3872     <thead>
3873      <row>
3874       <entry>Name</entry>
3875       <entry>Type</entry>
3876       <entry>References</entry>
3877       <entry>Description</entry>
3878      </row>
3879     </thead>
3880
3881     <tbody>
3882      <row>
3883       <entry><structfield>rulename</structfield></entry>
3884       <entry><type>name</type></entry>
3885       <entry></entry>
3886       <entry>Rule name</entry>
3887      </row>
3888
3889      <row>
3890       <entry><structfield>ev_class</structfield></entry>
3891       <entry><type>oid</type></entry>
3892       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
3893       <entry>The table this rule is for</entry>
3894      </row>
3895
3896      <row>
3897       <entry><structfield>ev_attr</structfield></entry>
3898       <entry><type>int2</type></entry>
3899       <entry></entry>
3900       <entry>The column this rule is for (currently, always zero to
3901       indicate the whole table)</entry>
3902      </row>
3903
3904      <row>
3905       <entry><structfield>ev_type</structfield></entry>
3906       <entry><type>char</type></entry>
3907       <entry></entry>
3908       <entry>
3909        Event type that the rule is for: 1 = <command>SELECT</>, 2 =
3910        <command>UPDATE</>, 3 = <command>INSERT</>, 4 =
3911        <command>DELETE</>
3912       </entry>
3913      </row>
3914
3915      <row>
3916       <entry><structfield>ev_enabled</structfield></entry>
3917       <entry><type>char</type></entry>
3918       <entry></entry>
3919       <entry>
3920        Controls in which <xref linkend="guc-session-replication-role"> modes
3921        the rule fires.
3922        <literal>O</> = rule fires in <quote>origin</> and <quote>local</> modes,
3923        <literal>D</> = rule is disabled,
3924        <literal>R</> = rule fires in <quote>replica</> mode,
3925        <literal>A</> = rule fires always.
3926       </entry>
3927      </row>
3928
3929      <row>
3930       <entry><structfield>is_instead</structfield></entry>
3931       <entry><type>bool</type></entry>
3932       <entry></entry>
3933       <entry>True if the rule is an <literal>INSTEAD</literal> rule</entry>
3934      </row>
3935
3936      <row>
3937       <entry><structfield>ev_qual</structfield></entry>
3938       <entry><type>text</type></entry>
3939       <entry></entry>
3940       <entry>
3941        Expression tree (in the form of a
3942        <function>nodeToString()</function> representation) for the
3943        rule's qualifying condition
3944       </entry>
3945      </row>
3946
3947      <row>
3948       <entry><structfield>ev_action</structfield></entry>
3949       <entry><type>text</type></entry>
3950       <entry></entry>
3951       <entry>
3952        Query tree (in the form of a
3953        <function>nodeToString()</function> representation) for the
3954        rule's action
3955       </entry>
3956      </row>
3957     </tbody>
3958    </tgroup>
3959   </table>
3960
3961   <note>
3962    <para>
3963     <literal>pg_class.relhasrules</literal>
3964     must be true if a table has any rules in this catalog.
3965    </para>
3966   </note>
3967
3968  </sect1>
3969
3970
3971  <sect1 id="catalog-pg-shdepend">
3972   <title><structname>pg_shdepend</structname></title>
3973
3974   <indexterm zone="catalog-pg-shdepend">
3975    <primary>pg_shdepend</primary>
3976   </indexterm>
3977
3978   <para>
3979    The catalog <structname>pg_shdepend</structname> records the
3980    dependency relationships between database objects and shared objects,
3981    such as roles.  This information allows
3982    <productname>PostgreSQL</productname> to ensure that those objects are
3983    unreferenced before attempting to delete them.
3984   </para>
3985
3986   <para>
3987    See also <link linkend="catalog-pg-depend"><structname>pg_depend</structname></link>,
3988    which performs a similar function for dependencies involving objects
3989    within a single database.
3990   </para>
3991
3992   <para>
3993    Unlike most system catalogs, <structname>pg_shdepend</structname>
3994    is shared across all databases of a cluster: there is only one
3995    copy of <structname>pg_shdepend</structname> per cluster, not
3996    one per database.
3997   </para>
3998
3999   <table>
4000    <title><structname>pg_shdepend</> Columns</title>
4001
4002    <tgroup cols="4">
4003     <thead>
4004      <row>
4005       <entry>Name</entry>
4006       <entry>Type</entry>
4007       <entry>References</entry>
4008       <entry>Description</entry>
4009      </row>
4010     </thead>
4011
4012     <tbody>
4013      <row>
4014       <entry><structfield>dbid</structfield></entry>
4015       <entry><type>oid</type></entry>
4016       <entry><literal><link linkend="catalog-pg-database"><structname>pg_database</structname></link>.oid</literal></entry>
4017       <entry>The OID of the database the dependent object is in,
4018        or zero for a shared object</entry>
4019      </row>
4020
4021      <row>
4022       <entry><structfield>classid</structfield></entry>
4023       <entry><type>oid</type></entry>
4024       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
4025       <entry>The OID of the system catalog the dependent object is in</entry>
4026      </row>
4027
4028      <row>
4029       <entry><structfield>objid</structfield></entry>
4030       <entry><type>oid</type></entry>
4031       <entry>any OID column</entry>
4032       <entry>The OID of the specific dependent object</entry>
4033      </row>
4034
4035      <row>
4036       <entry><structfield>objsubid</structfield></entry>
4037       <entry><type>int4</type></entry>
4038       <entry></entry>
4039       <entry>
4040        For a table column, this is the column number (the
4041        <structfield>objid</> and <structfield>classid</> refer to the
4042        table itself).  For all other object types, this column is zero
4043       </entry>
4044      </row>
4045
4046      <row>
4047       <entry><structfield>refclassid</structfield></entry>
4048       <entry><type>oid</type></entry>
4049       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
4050       <entry>The OID of the system catalog the referenced object is in
4051        (must be a shared catalog)</entry>
4052      </row>
4053
4054      <row>
4055       <entry><structfield>refobjid</structfield></entry>
4056       <entry><type>oid</type></entry>
4057       <entry>any OID column</entry>
4058       <entry>The OID of the specific referenced object</entry>
4059      </row>
4060
4061      <row>
4062       <entry><structfield>deptype</structfield></entry>
4063       <entry><type>char</type></entry>
4064       <entry></entry>
4065       <entry>
4066        A code defining the specific semantics of this dependency relationship; see text
4067       </entry>
4068      </row>
4069
4070     </tbody>
4071    </tgroup>
4072   </table>
4073
4074   <para>
4075    In all cases, a <structname>pg_shdepend</structname> entry indicates that
4076    the referenced object cannot be dropped without also dropping the dependent
4077    object.  However, there are several subflavors identified by
4078    <structfield>deptype</>:
4079
4080    <variablelist>
4081     <varlistentry>
4082      <term><symbol>SHARED_DEPENDENCY_OWNER</> (<literal>o</>)</term>
4083      <listitem>
4084       <para>
4085        The referenced object (which must be a role) is the owner of the
4086        dependent object.
4087       </para>
4088      </listitem>
4089     </varlistentry>
4090
4091     <varlistentry>
4092      <term><symbol>SHARED_DEPENDENCY_ACL</> (<literal>a</>)</term>
4093      <listitem>
4094       <para>
4095        The referenced object (which must be a role) is mentioned in the
4096        ACL (access control list, i.e., privileges list) of the
4097        dependent object.  (A <symbol>SHARED_DEPENDENCY_ACL</> entry is
4098        not made for the owner of the object, since the owner will have
4099        a <symbol>SHARED_DEPENDENCY_OWNER</> entry anyway.)
4100       </para>
4101      </listitem>
4102     </varlistentry>
4103
4104     <varlistentry>
4105      <term><symbol>SHARED_DEPENDENCY_PIN</> (<literal>p</>)</term>
4106      <listitem>
4107       <para>
4108        There is no dependent object; this type of entry is a signal
4109        that the system itself depends on the referenced object, and so
4110        that object must never be deleted.  Entries of this type are
4111        created only by <command>initdb</command>.  The columns for the
4112        dependent object contain zeroes.
4113       </para>
4114      </listitem>
4115     </varlistentry>
4116    </variablelist>
4117
4118    Other dependency flavors might be needed in future.  Note in particular
4119    that the current definition only supports roles as referenced objects.
4120   </para>
4121
4122  </sect1>
4123
4124  <sect1 id="catalog-pg-shdescription">
4125   <title><structname>pg_shdescription</structname></title>
4126
4127   <indexterm zone="catalog-pg-shdescription">
4128    <primary>pg_shdescription</primary>
4129   </indexterm>
4130
4131   <para>
4132    The catalog <structname>pg_shdescription</structname> stores optional
4133    descriptions (comments) for shared database objects.  Descriptions can be
4134    manipulated with the <xref linkend="sql-comment"
4135    endterm="sql-comment-title"> command and viewed with
4136    <application>psql</application>'s <literal>\d</literal> commands.
4137   </para>
4138
4139   <para>
4140    See also <link linkend="catalog-pg-description"><structname>pg_description</structname></link>,
4141    which performs a similar function for descriptions involving objects
4142    within a single database.
4143   </para>
4144
4145   <para>
4146    Unlike most system catalogs, <structname>pg_shdescription</structname>
4147    is shared across all databases of a cluster: there is only one
4148    copy of <structname>pg_shdescription</structname> per cluster, not
4149    one per database.
4150   </para>
4151
4152   <table>
4153    <title><structname>pg_shdescription</> Columns</title>
4154
4155    <tgroup cols="4">
4156     <thead>
4157      <row>
4158       <entry>Name</entry>
4159       <entry>Type</entry>
4160       <entry>References</entry>
4161       <entry>Description</entry>
4162      </row>
4163     </thead>
4164
4165     <tbody>
4166      <row>
4167       <entry><structfield>objoid</structfield></entry>
4168       <entry><type>oid</type></entry>
4169       <entry>any OID column</entry>
4170       <entry>The OID of the object this description pertains to</entry>
4171      </row>
4172
4173      <row>
4174       <entry><structfield>classoid</structfield></entry>
4175       <entry><type>oid</type></entry>
4176       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
4177       <entry>The OID of the system catalog this object appears in</entry>
4178      </row>
4179
4180      <row>
4181       <entry><structfield>description</structfield></entry>
4182       <entry><type>text</type></entry>
4183       <entry></entry>
4184       <entry>Arbitrary text that serves as the description of this object</entry>
4185      </row>
4186     </tbody>
4187    </tgroup>
4188   </table>
4189
4190  </sect1>
4191
4192
4193  <sect1 id="catalog-pg-statistic">
4194   <title><structname>pg_statistic</structname></title>
4195
4196   <indexterm zone="catalog-pg-statistic">
4197    <primary>pg_statistic</primary>
4198   </indexterm>
4199
4200   <para>
4201    The catalog <structname>pg_statistic</structname> stores
4202    statistical data about the contents of the database.  Entries are
4203    created by <xref linkend="sql-analyze" endterm="sql-analyze-title">
4204    and subsequently used by the query planner.  There is one entry for
4205    each table column that has been analyzed.  Note that all the
4206    statistical data is inherently approximate, even assuming that it
4207    is up-to-date.
4208   </para>
4209
4210   <para>
4211    <structname>pg_statistic</structname> also stores statistical data about
4212    the values of index expressions.  These are described as if they were
4213    actual data columns; in particular, <structfield>starelid</structfield>
4214    references the index.  No entry is made for an ordinary non-expression
4215    index column, however, since it would be redundant with the entry
4216    for the underlying table column.
4217   </para>
4218
4219   <para>
4220    Since different kinds of statistics might be appropriate for different
4221    kinds of data, <structname>pg_statistic</structname> is designed not
4222    to assume very much about what sort of statistics it stores.  Only
4223    extremely general statistics (such as nullness) are given dedicated
4224    columns in <structname>pg_statistic</structname>.  Everything else
4225    is stored in <quote>slots</quote>, which are groups of associated columns
4226    whose content is identified by a code number in one of the slot's columns.
4227    For more information see
4228    <filename>src/include/catalog/pg_statistic.h</filename>.
4229   </para>
4230
4231   <para>
4232    <structname>pg_statistic</structname> should not be readable by the
4233    public, since even statistical information about a table's contents
4234    might be considered sensitive.  (Example: minimum and maximum values
4235    of a salary column might be quite interesting.)
4236    <link linkend="view-pg-stats"><structname>pg_stats</structname></link>
4237    is a publicly readable view on
4238    <structname>pg_statistic</structname> that only exposes information
4239    about those tables that are readable by the current user.
4240   </para>
4241
4242   <table>
4243    <title><structname>pg_statistic</> Columns</title>
4244
4245    <tgroup cols="4">
4246     <thead>
4247      <row>
4248       <entry>Name</entry>
4249       <entry>Type</entry>
4250       <entry>References</entry>
4251       <entry>Description</entry>
4252      </row>
4253     </thead>
4254
4255     <tbody>
4256      <row>
4257       <entry><structfield>starelid</structfield></entry>
4258       <entry><type>oid</type></entry>
4259       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
4260       <entry>The table or index that the described column belongs to</entry>
4261      </row>
4262
4263      <row>
4264       <entry><structfield>staattnum</structfield></entry>
4265       <entry><type>int2</type></entry>
4266       <entry><literal><link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.attnum</literal></entry>
4267       <entry>The number of the described column</entry>
4268      </row>
4269
4270      <row>
4271       <entry><structfield>stanullfrac</structfield></entry>
4272       <entry><type>float4</type></entry>
4273       <entry></entry>
4274       <entry>The fraction of the column's entries that are null</entry>
4275      </row>
4276
4277      <row>
4278       <entry><structfield>stawidth</structfield></entry>
4279       <entry><type>int4</type></entry>
4280       <entry></entry>
4281       <entry>The average stored width, in bytes, of nonnull entries</entry>
4282      </row>
4283
4284      <row>
4285       <entry><structfield>stadistinct</structfield></entry>
4286       <entry><type>float4</type></entry>
4287       <entry></entry>
4288       <entry>The number of distinct nonnull data values in the column.
4289       A value greater than zero is the actual number of distinct values.
4290       A value less than zero is the negative of a fraction of the number
4291       of rows in the table (for example, a column in which values appear about
4292       twice on the average could be represented by <structfield>stadistinct</> = -0.5).
4293       A zero value means the number of distinct values is unknown
4294       </entry>
4295      </row>
4296
4297      <row>
4298       <entry><structfield>stakind<replaceable>N</></structfield></entry>
4299       <entry><type>int2</type></entry>
4300       <entry></entry>
4301       <entry>
4302        A code number indicating the kind of statistics stored in the
4303        <replaceable>N</>th <quote>slot</quote> of the
4304        <structname>pg_statistic</structname> row
4305       </entry>
4306      </row>
4307
4308      <row>
4309       <entry><structfield>staop<replaceable>N</></structfield></entry>
4310       <entry><type>oid</type></entry>
4311       <entry><literal><link linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.oid</literal></entry>
4312       <entry>
4313        An operator used to derive the statistics stored in the
4314        <replaceable>N</>th <quote>slot</quote>.  For example, a
4315        histogram slot would show the <literal>&lt;</literal> operator
4316        that defines the sort order of the data
4317       </entry>
4318      </row>
4319
4320      <row>
4321       <entry><structfield>stanumbers<replaceable>N</></structfield></entry>
4322       <entry><type>float4[]</type></entry>
4323       <entry></entry>
4324       <entry>
4325        Numerical statistics of the appropriate kind for the
4326        <replaceable>N</>th <quote>slot</quote>, or NULL if the slot
4327        kind does not involve numerical values
4328       </entry>
4329      </row>
4330
4331      <row>
4332       <entry><structfield>stavalues<replaceable>N</></structfield></entry>
4333       <entry><type>anyarray</type></entry>
4334       <entry></entry>
4335       <entry>
4336        Column data values of the appropriate kind for the
4337        <replaceable>N</>th <quote>slot</quote>, or NULL if the slot
4338        kind does not store any data values.  Each array's element
4339        values are actually of the specific column's data type, so there
4340        is no way to define these columns' type more specifically than
4341        <type>anyarray</>
4342       </entry>
4343      </row>
4344     </tbody>
4345    </tgroup>
4346   </table>
4347
4348  </sect1>
4349
4350
4351  <sect1 id="catalog-pg-tablespace">
4352   <title><structname>pg_tablespace</structname></title>
4353
4354   <indexterm zone="catalog-pg-tablespace">
4355    <primary>pg_tablespace</primary>
4356   </indexterm>
4357
4358   <para>
4359    The catalog <structname>pg_tablespace</structname> stores information
4360    about the available tablespaces.  Tables can be placed in particular
4361    tablespaces to aid administration of disk layout.
4362   </para>
4363
4364   <para>
4365    Unlike most system catalogs, <structname>pg_tablespace</structname>
4366    is shared across all databases of a cluster: there is only one
4367    copy of <structname>pg_tablespace</structname> per cluster, not
4368    one per database.
4369   </para>
4370
4371   <table>
4372    <title><structname>pg_tablespace</> Columns</title>
4373
4374    <tgroup cols="4">
4375     <thead>
4376      <row>
4377       <entry>Name</entry>
4378       <entry>Type</entry>
4379       <entry>References</entry>
4380       <entry>Description</entry>
4381      </row>
4382     </thead>
4383
4384     <tbody>
4385      <row>
4386       <entry><structfield>spcname</structfield></entry>
4387       <entry><type>name</type></entry>
4388       <entry></entry>
4389       <entry>Tablespace name</entry>
4390      </row>
4391
4392      <row>
4393       <entry><structfield>spcowner</structfield></entry>
4394       <entry><type>oid</type></entry>
4395       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
4396       <entry>Owner of the tablespace, usually the user who created it</entry>
4397      </row>
4398
4399      <row>
4400       <entry><structfield>spclocation</structfield></entry>
4401       <entry><type>text</type></entry>
4402       <entry></entry>
4403       <entry>Location (directory path) of the tablespace</entry>
4404      </row>
4405
4406      <row>
4407       <entry><structfield>spcacl</structfield></entry>
4408       <entry><type>aclitem[]</type></entry>
4409       <entry></entry>
4410       <entry>
4411        Access privileges; see
4412        <xref linkend="sql-grant" endterm="sql-grant-title"> and
4413        <xref linkend="sql-revoke" endterm="sql-revoke-title">
4414        for details
4415       </entry>
4416      </row>
4417     </tbody>
4418    </tgroup>
4419   </table>
4420  </sect1>
4421
4422
4423  <sect1 id="catalog-pg-trigger">
4424   <title><structname>pg_trigger</structname></title>
4425
4426   <indexterm zone="catalog-pg-trigger">
4427    <primary>pg_trigger</primary>
4428   </indexterm>
4429
4430   <para>
4431    The catalog <structname>pg_trigger</structname> stores triggers on tables.
4432    See <xref linkend="sql-createtrigger" endterm="sql-createtrigger-title">
4433    for more information.
4434   </para>
4435
4436   <table>
4437    <title><structname>pg_trigger</> Columns</title>
4438
4439    <tgroup cols="4">
4440     <thead>
4441      <row>
4442       <entry>Name</entry>
4443       <entry>Type</entry>
4444       <entry>References</entry>
4445       <entry>Description</entry>
4446      </row>
4447     </thead>
4448
4449     <tbody>
4450      <row>
4451       <entry><structfield>tgrelid</structfield></entry>
4452       <entry><type>oid</type></entry>
4453       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
4454       <entry>The table this trigger is on</entry>
4455      </row>
4456
4457      <row>
4458       <entry><structfield>tgname</structfield></entry>
4459       <entry><type>name</type></entry>
4460       <entry></entry>
4461       <entry>Trigger name (must be unique among triggers of same table)</entry>
4462      </row>
4463
4464      <row>
4465       <entry><structfield>tgfoid</structfield></entry>
4466       <entry><type>oid</type></entry>
4467       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
4468       <entry>The function to be called</entry>
4469      </row>
4470
4471      <row>
4472       <entry><structfield>tgtype</structfield></entry>
4473       <entry><type>int2</type></entry>
4474       <entry></entry>
4475       <entry>Bit mask identifying trigger conditions</entry>
4476      </row>
4477
4478      <row>
4479       <entry><structfield>tgenabled</structfield></entry>
4480       <entry><type>char</type></entry>
4481       <entry></entry>
4482       <entry>
4483        Controls in which <xref linkend="guc-session-replication-role"> modes
4484        the trigger fires.
4485        <literal>O</> = trigger fires in <quote>origin</> and <quote>local</> modes,
4486        <literal>D</> = trigger is disabled,
4487        <literal>R</> = trigger fires in <quote>replica</> mode,
4488        <literal>A</> = trigger fires always.
4489       </entry>
4490      </row>
4491
4492      <row>
4493       <entry><structfield>tgisconstraint</structfield></entry>
4494       <entry><type>bool</type></entry>
4495       <entry></entry>
4496       <entry>True if trigger is a <quote>constraint trigger</></entry>
4497      </row>
4498
4499      <row>
4500       <entry><structfield>tgconstrname</structfield></entry>
4501       <entry><type>name</type></entry>
4502       <entry></entry>
4503       <entry>Constraint name, if a constraint trigger</entry>
4504      </row>
4505
4506      <row>
4507       <entry><structfield>tgconstrrelid</structfield></entry>
4508       <entry><type>oid</type></entry>
4509       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
4510       <entry>The table referenced by a referential integrity constraint</entry>
4511      </row>
4512
4513      <row>
4514       <entry><structfield>tgconstraint</structfield></entry>
4515       <entry><type>oid</type></entry>
4516       <entry><literal><link linkend="catalog-pg-constraint"><structname>pg_constraint</structname></link>.oid</literal></entry>
4517       <entry>The <structname>pg_constraint</> entry owning the trigger, if any</entry>
4518      </row>
4519
4520      <row>
4521       <entry><structfield>tgdeferrable</structfield></entry>
4522       <entry><type>bool</type></entry>
4523       <entry></entry>
4524       <entry>True if constraint trigger is deferrable</entry>
4525      </row>
4526
4527      <row>
4528       <entry><structfield>tginitdeferred</structfield></entry>
4529       <entry><type>bool</type></entry>
4530       <entry></entry>
4531       <entry>True if constraint trigger is initially deferred</entry>
4532      </row>
4533
4534      <row>
4535       <entry><structfield>tgnargs</structfield></entry>
4536       <entry><type>int2</type></entry>
4537       <entry></entry>
4538       <entry>Number of argument strings passed to trigger function</entry>
4539      </row>
4540
4541      <row>
4542       <entry><structfield>tgattr</structfield></entry>
4543       <entry><type>int2vector</type></entry>
4544       <entry></entry>
4545       <entry>Currently unused</entry>
4546      </row>
4547
4548      <row>
4549       <entry><structfield>tgargs</structfield></entry>
4550       <entry><type>bytea</type></entry>
4551       <entry></entry>
4552       <entry>Argument strings to pass to trigger, each NULL-terminated</entry>
4553      </row>
4554     </tbody>
4555    </tgroup>
4556   </table>
4557
4558   <note>
4559    <para>
4560     When <structfield>tgconstraint</> is nonzero,
4561     <structfield>tgisconstraint</> must be true, and
4562     <structfield>tgconstrname</>, <structfield>tgconstrrelid</>,
4563     <structfield>tgdeferrable</>, <structfield>tginitdeferred</> are redundant
4564     with the referenced <structname>pg_constraint</> entry.  The reason we
4565     keep these fields is that we support <quote>stand-alone</> constraint
4566     triggers with no corresponding <structname>pg_constraint</> entry.
4567    </para>
4568   </note>
4569
4570   <note>
4571    <para>
4572     <literal>pg_class.relhastriggers</literal>
4573     must be true if a table has any triggers in this catalog.
4574    </para>
4575   </note>
4576
4577  </sect1>
4578
4579
4580  <sect1 id="catalog-pg-ts-config">
4581   <title><structname>pg_ts_config</structname></title>
4582
4583   <indexterm zone="catalog-pg-ts-config">
4584    <primary>pg_ts_config</primary>
4585   </indexterm>
4586
4587   <para>
4588    The <structname>pg_ts_config</structname> catalog contains entries
4589    representing text search configurations.  A configuration specifies
4590    a particular text search parser and a list of dictionaries to use
4591    for each of the parser's output token types.  The parser is shown
4592    in the <structname>pg_ts_config</structname> entry, but the
4593    token-to-dictionary mapping is defined by subsidiary entries in <link
4594    linkend="catalog-pg-ts-config-map"><structname>pg_ts_config_map</structname></link>.
4595   </para>
4596
4597   <para>
4598    <productname>PostgreSQL</productname>'s text search features are
4599    described at length in <xref linkend="textsearch">.
4600   </para>
4601
4602   <table>
4603    <title><structname>pg_ts_config</> Columns</title>
4604
4605    <tgroup cols="4">
4606     <thead>
4607      <row>
4608       <entry>Name</entry>
4609       <entry>Type</entry>
4610       <entry>References</entry>
4611       <entry>Description</entry>
4612      </row>
4613     </thead>
4614
4615     <tbody>
4616      <row>
4617       <entry><structfield>cfgname</structfield></entry>
4618       <entry><type>name</type></entry>
4619       <entry></entry>
4620       <entry>Text search configuration name</entry>
4621      </row>
4622
4623      <row>
4624       <entry><structfield>cfgnamespace</structfield></entry>
4625       <entry><type>oid</type></entry>
4626       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>
4627       <entry>
4628        The OID of the namespace that contains this configuration
4629       </entry>
4630      </row>
4631
4632      <row>
4633       <entry><structfield>cfgowner</structfield></entry>
4634       <entry><type>oid</type></entry>
4635       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
4636       <entry>Owner of the configuration</entry>
4637      </row>
4638
4639      <row>
4640       <entry><structfield>cfgparser</structfield></entry>
4641       <entry><type>oid</type></entry>
4642       <entry><literal><link linkend="catalog-pg-ts-parser"><structname>pg_ts_parser</structname></link>.oid</literal></entry>
4643       <entry>The OID of the text search parser for this configuration</entry>
4644      </row>
4645     </tbody>
4646    </tgroup>
4647   </table>
4648  </sect1>
4649
4650
4651  <sect1 id="catalog-pg-ts-config-map">
4652   <title><structname>pg_ts_config_map</structname></title>
4653
4654   <indexterm zone="catalog-pg-ts-config-map">
4655    <primary>pg_ts_config_map</primary>
4656   </indexterm>
4657
4658   <para>
4659    The <structname>pg_ts_config_map</structname> catalog contains entries
4660    showing which text search dictionaries should be consulted, and in
4661    what order, for each output token type of each text search configuration's
4662    parser.
4663   </para>
4664
4665   <para>
4666    <productname>PostgreSQL</productname>'s text search features are
4667    described at length in <xref linkend="textsearch">.
4668   </para>
4669
4670   <table>
4671    <title><structname>pg_ts_config_map</> Columns</title>
4672
4673    <tgroup cols="4">
4674     <thead>
4675      <row>
4676       <entry>Name</entry>
4677       <entry>Type</entry>
4678       <entry>References</entry>
4679       <entry>Description</entry>
4680      </row>
4681     </thead>
4682
4683     <tbody>
4684      <row>
4685       <entry><structfield>mapcfg</structfield></entry>
4686       <entry><type>oid</type></entry>
4687       <entry><literal><link linkend="catalog-pg-ts-config"><structname>pg_ts_config</structname></link>.oid</literal></entry>
4688       <entry>The OID of the <structname>pg_ts_config</> entry owning this map entry</entry>
4689      </row>
4690
4691      <row>
4692       <entry><structfield>maptokentype</structfield></entry>
4693       <entry><type>integer</type></entry>
4694       <entry></entry>
4695       <entry>A token type emitted by the configuration's parser</entry>
4696      </row>
4697
4698      <row>
4699       <entry><structfield>mapseqno</structfield></entry>
4700       <entry><type>integer</type></entry>
4701       <entry></entry>
4702       <entry>Order in which to consult this entry (lower
4703        <structfield>mapseqno</>s first)</entry>
4704      </row>
4705
4706      <row>
4707       <entry><structfield>mapdict</structfield></entry>
4708       <entry><type>oid</type></entry>
4709       <entry><literal><link linkend="catalog-pg-ts-dict"><structname>pg_ts_dict</structname></link>.oid</literal></entry>
4710       <entry>The OID of the text search dictionary to consult</entry>
4711      </row>
4712     </tbody>
4713    </tgroup>
4714   </table>
4715  </sect1>
4716
4717
4718  <sect1 id="catalog-pg-ts-dict">
4719   <title><structname>pg_ts_dict</structname></title>
4720
4721   <indexterm zone="catalog-pg-ts-dict">
4722    <primary>pg_ts_dict</primary>
4723   </indexterm>
4724
4725   <para>
4726    The <structname>pg_ts_dict</structname> catalog contains entries
4727    defining text search dictionaries.  A dictionary depends on a text
4728    search template, which specifies all the implementation functions
4729    needed; the dictionary itself provides values for the user-settable
4730    parameters supported by the template.  This division of labor allows
4731    dictionaries to be created by unprivileged users.  The parameters
4732    are specified by a text string <structfield>dictinitoption</>,
4733    whose format and meaning vary depending on the template.
4734   </para>
4735
4736   <para>
4737    <productname>PostgreSQL</productname>'s text search features are
4738    described at length in <xref linkend="textsearch">.
4739   </para>
4740
4741   <table>
4742    <title><structname>pg_ts_dict</> Columns</title>
4743
4744    <tgroup cols="4">
4745     <thead>
4746      <row>
4747       <entry>Name</entry>
4748       <entry>Type</entry>
4749       <entry>References</entry>
4750       <entry>Description</entry>
4751      </row>
4752     </thead>
4753
4754     <tbody>
4755      <row>
4756       <entry><structfield>dictname</structfield></entry>
4757       <entry><type>name</type></entry>
4758       <entry></entry>
4759       <entry>Text search dictionary name</entry>
4760      </row>
4761
4762      <row>
4763       <entry><structfield>dictnamespace</structfield></entry>
4764       <entry><type>oid</type></entry>
4765       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>
4766       <entry>
4767        The OID of the namespace that contains this dictionary
4768       </entry>
4769      </row>
4770
4771      <row>
4772       <entry><structfield>dictowner</structfield></entry>
4773       <entry><type>oid</type></entry>
4774       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
4775       <entry>Owner of the dictionary</entry>
4776      </row>
4777
4778      <row>
4779       <entry><structfield>dicttemplate</structfield></entry>
4780       <entry><type>oid</type></entry>
4781       <entry><literal><link linkend="catalog-pg-ts-template"><structname>pg_ts_template</structname></link>.oid</literal></entry>
4782       <entry>The OID of the text search template for this dictionary</entry>
4783      </row>
4784
4785      <row>
4786       <entry><structfield>dictinitoption</structfield></entry>
4787       <entry><type>text</type></entry>
4788       <entry></entry>
4789       <entry>Initialization option string for the template</entry>
4790      </row>
4791     </tbody>
4792    </tgroup>
4793   </table>
4794  </sect1>
4795
4796
4797  <sect1 id="catalog-pg-ts-parser">
4798   <title><structname>pg_ts_parser</structname></title>
4799
4800   <indexterm zone="catalog-pg-ts-parser">
4801    <primary>pg_ts_parser</primary>
4802   </indexterm>
4803
4804   <para>
4805    The <structname>pg_ts_parser</structname> catalog contains entries
4806    defining text search parsers.  A parser is responsible for splitting
4807    input text into lexemes and assigning a token type to each lexeme.
4808    Since a parser must be implemented by C-language-level functions,
4809    creation of new parsers is restricted to database superusers.
4810   </para>
4811
4812   <para>
4813    <productname>PostgreSQL</productname>'s text search features are
4814    described at length in <xref linkend="textsearch">.
4815   </para>
4816
4817   <table>
4818    <title><structname>pg_ts_parser</> Columns</title>
4819
4820    <tgroup cols="4">
4821     <thead>
4822      <row>
4823       <entry>Name</entry>
4824       <entry>Type</entry>
4825       <entry>References</entry>
4826       <entry>Description</entry>
4827      </row>
4828     </thead>
4829
4830     <tbody>
4831      <row>
4832       <entry><structfield>prsname</structfield></entry>
4833       <entry><type>name</type></entry>
4834       <entry></entry>
4835       <entry>Text search parser name</entry>
4836      </row>
4837
4838      <row>
4839       <entry><structfield>prsnamespace</structfield></entry>
4840       <entry><type>oid</type></entry>
4841       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>
4842       <entry>
4843        The OID of the namespace that contains this parser
4844       </entry>
4845      </row>
4846
4847      <row>
4848       <entry><structfield>prsstart</structfield></entry>
4849       <entry><type>regproc</type></entry>
4850       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
4851       <entry>OID of the parser's startup function</entry>
4852      </row>
4853
4854      <row>
4855       <entry><structfield>prstoken</structfield></entry>
4856       <entry><type>regproc</type></entry>
4857       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
4858       <entry>OID of the parser's next-token function</entry>
4859      </row>
4860
4861      <row>
4862       <entry><structfield>prsend</structfield></entry>
4863       <entry><type>regproc</type></entry>
4864       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
4865       <entry>OID of the parser's shutdown function</entry>
4866      </row>
4867
4868      <row>
4869       <entry><structfield>prsheadline</structfield></entry>
4870       <entry><type>regproc</type></entry>
4871       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
4872       <entry>OID of the parser's headline function</entry>
4873      </row>
4874
4875      <row>
4876       <entry><structfield>prslextype</structfield></entry>
4877       <entry><type>regproc</type></entry>
4878       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
4879       <entry>OID of the parser's lextype function</entry>
4880      </row>
4881     </tbody>
4882    </tgroup>
4883   </table>
4884  </sect1>
4885
4886
4887  <sect1 id="catalog-pg-ts-template">
4888   <title><structname>pg_ts_template</structname></title>
4889
4890   <indexterm zone="catalog-pg-ts-template">
4891    <primary>pg_ts_template</primary>
4892   </indexterm>
4893
4894   <para>
4895    The <structname>pg_ts_template</structname> catalog contains entries
4896    defining text search templates.  A template is the implementation
4897    skeleton for a class of text search dictionaries.
4898    Since a template must be implemented by C-language-level functions,
4899    creation of new templates is restricted to database superusers.
4900   </para>
4901
4902   <para>
4903    <productname>PostgreSQL</productname>'s text search features are
4904    described at length in <xref linkend="textsearch">.
4905   </para>
4906
4907   <table>
4908    <title><structname>pg_ts_template</> Columns</title>
4909
4910    <tgroup cols="4">
4911     <thead>
4912      <row>
4913       <entry>Name</entry>
4914       <entry>Type</entry>
4915       <entry>References</entry>
4916       <entry>Description</entry>
4917      </row>
4918     </thead>
4919
4920     <tbody>
4921      <row>
4922       <entry><structfield>tmplname</structfield></entry>
4923       <entry><type>name</type></entry>
4924       <entry></entry>
4925       <entry>Text search template name</entry>
4926      </row>
4927
4928      <row>
4929       <entry><structfield>tmplnamespace</structfield></entry>
4930       <entry><type>oid</type></entry>
4931       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>
4932       <entry>
4933        The OID of the namespace that contains this template
4934       </entry>
4935      </row>
4936
4937      <row>
4938       <entry><structfield>tmplinit</structfield></entry>
4939       <entry><type>regproc</type></entry>
4940       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
4941       <entry>OID of the template's initialization function</entry>
4942      </row>
4943
4944      <row>
4945       <entry><structfield>tmpllexize</structfield></entry>
4946       <entry><type>regproc</type></entry>
4947       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
4948       <entry>OID of the template's lexize function</entry>
4949      </row>
4950     </tbody>
4951    </tgroup>
4952   </table>
4953  </sect1>
4954
4955
4956  <sect1 id="catalog-pg-type">
4957   <title><structname>pg_type</structname></title>
4958
4959   <indexterm zone="catalog-pg-type">
4960    <primary>pg_type</primary>
4961   </indexterm>
4962
4963   <para>
4964    The catalog <structname>pg_type</structname> stores information about data
4965    types.  Base types and enum types (scalar types) are created with
4966    <xref linkend="sql-createtype" endterm="sql-createtype-title">, and
4967    domains with
4968    <xref linkend="sql-createdomain" endterm="sql-createdomain-title">.
4969    A composite type is automatically created for each table in the database, to
4970    represent the row structure of the table.  It is also possible to create
4971    composite types with <command>CREATE TYPE AS</command>.
4972   </para>
4973
4974   <table>
4975    <title><structname>pg_type</> Columns</title>
4976
4977    <tgroup cols="4">
4978     <thead>
4979      <row>
4980       <entry>Name</entry>
4981       <entry>Type</entry>
4982       <entry>References</entry>
4983       <entry>Description</entry>
4984      </row>
4985     </thead>
4986
4987     <tbody>
4988      <row>
4989       <entry><structfield>typname</structfield></entry>
4990       <entry><type>name</type></entry>
4991       <entry></entry>
4992       <entry>Data type name</entry>
4993      </row>
4994
4995      <row>
4996       <entry><structfield>typnamespace</structfield></entry>
4997       <entry><type>oid</type></entry>
4998       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>
4999       <entry>
5000        The OID of the namespace that contains this type
5001       </entry>
5002      </row>
5003
5004      <row>
5005       <entry><structfield>typowner</structfield></entry>
5006       <entry><type>oid</type></entry>
5007       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
5008       <entry>Owner of the type</entry>
5009      </row>
5010
5011      <row>
5012       <entry><structfield>typlen</structfield></entry>
5013       <entry><type>int2</type></entry>
5014       <entry></entry>
5015       <entry>
5016        For a fixed-size type, <structfield>typlen</structfield> is the number
5017        of bytes in the internal representation of the type.  But for a
5018        variable-length type, <structfield>typlen</structfield> is negative.
5019        -1 indicates a <quote>varlena</> type (one that has a length word),
5020        -2 indicates a null-terminated C string.
5021       </entry>
5022      </row>
5023
5024      <row>
5025       <entry><structfield>typbyval</structfield></entry>
5026       <entry><type>bool</type></entry>
5027       <entry></entry>
5028       <entry>
5029        <structfield>typbyval</structfield> determines whether internal
5030        routines pass a value of this type by value or by reference.
5031        <structfield>typbyval</structfield> had better be false if
5032        <structfield>typlen</structfield> is not 1, 2, or 4 (or 8 on machines
5033        where Datum is 8 bytes).
5034        Variable-length types are always passed by reference. Note that
5035        <structfield>typbyval</structfield> can be false even if the
5036        length would allow pass-by-value
5037       </entry>
5038      </row>
5039
5040      <row>
5041       <entry><structfield>typtype</structfield></entry>
5042       <entry><type>char</type></entry>
5043       <entry></entry>
5044       <entry>
5045        <structfield>typtype</structfield> is
5046        <literal>b</literal> for a base type,
5047        <literal>c</literal> for a composite type (e.g., a table's row type),
5048        <literal>d</literal> for a domain,
5049        <literal>e</literal> for an enum type,
5050        or <literal>p</literal> for a pseudo-type.
5051        See also <structfield>typrelid</structfield> and
5052        <structfield>typbasetype</structfield>
5053       </entry>
5054      </row>
5055
5056      <row>
5057       <entry><structfield>typcategory</structfield></entry>
5058       <entry><type>char</type></entry>
5059       <entry></entry>
5060       <entry>
5061        <structfield>typcategory</structfield> is an arbitrary classification
5062        of data types that is used by the parser to determine which implicit
5063        casts should be <quote>preferred</>.
5064        See <xref linkend="catalog-typcategory-table">
5065       </entry>
5066      </row>
5067
5068      <row>
5069       <entry><structfield>typispreferred</structfield></entry>
5070       <entry><type>bool</type></entry>
5071       <entry></entry>
5072       <entry>
5073        True if the type is a preferred cast target within its
5074        <structfield>typcategory</structfield>
5075       </entry>
5076      </row>
5077
5078      <row>
5079       <entry><structfield>typisdefined</structfield></entry>
5080       <entry><type>bool</type></entry>
5081       <entry></entry>
5082       <entry>
5083        True if the type is defined, false if this is a placeholder
5084        entry for a not-yet-defined type.  When
5085        <structfield>typisdefined</structfield> is false, nothing
5086        except the type name, namespace, and OID can be relied on
5087       </entry>
5088      </row>
5089
5090      <row>
5091       <entry><structfield>typdelim</structfield></entry>
5092       <entry><type>char</type></entry>
5093       <entry></entry>
5094       <entry>
5095        Character that separates two values of this type when parsing
5096        array input.  Note that the delimiter is associated with the array
5097        element data type, not the array data type
5098       </entry>
5099      </row>
5100
5101      <row>
5102       <entry><structfield>typrelid</structfield></entry>
5103       <entry><type>oid</type></entry>
5104       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
5105       <entry>
5106        If this is a composite type (see
5107        <structfield>typtype</structfield>), then this column points to
5108        the <structname>pg_class</structname> entry that defines the
5109        corresponding table.  (For a free-standing composite type, the
5110        <structname>pg_class</structname> entry doesn't really represent
5111        a table, but it is needed anyway for the type's
5112        <structname>pg_attribute</structname> entries to link to.)
5113        Zero for non-composite types
5114       </entry>
5115      </row>
5116
5117      <row>
5118       <entry><structfield>typelem</structfield></entry>
5119       <entry><type>oid</type></entry>
5120       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
5121       <entry>
5122        If <structfield>typelem</structfield> is not 0 then it
5123        identifies another row in <structname>pg_type</structname>.
5124        The current type can then be subscripted like an array yielding
5125        values of type <structfield>typelem</structfield>.  A
5126        <quote>true</quote> array type is variable length
5127        (<structfield>typlen</structfield> = -1),
5128        but some fixed-length (<structfield>typlen</structfield> &gt; 0) types
5129        also have nonzero <structfield>typelem</structfield>, for example
5130        <type>name</type> and <type>point</type>.
5131        If a fixed-length type has a <structfield>typelem</structfield> then
5132        its internal representation must be some number of values of the
5133        <structfield>typelem</structfield> data type with no other data.
5134        Variable-length array types have a header defined by the array
5135        subroutines
5136       </entry>
5137      </row>
5138
5139      <row>
5140       <entry><structfield>typarray</structfield></entry>
5141       <entry><type>oid</type></entry>
5142       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
5143       <entry>
5144        If <structfield>typarray</structfield> is not 0 then it
5145        identifies another row in <structname>pg_type</structname>, which
5146        is the <quote>true</quote> array type having this type as element
5147       </entry>
5148      </row>
5149
5150      <row>
5151       <entry><structfield>typinput</structfield></entry>
5152       <entry><type>regproc</type></entry>
5153       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
5154       <entry>Input conversion function (text format)</entry>
5155      </row>
5156
5157      <row>
5158       <entry><structfield>typoutput</structfield></entry>
5159       <entry><type>regproc</type></entry>
5160       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
5161       <entry>Output conversion function (text format)</entry>
5162      </row>
5163
5164      <row>
5165       <entry><structfield>typreceive</structfield></entry>
5166       <entry><type>regproc</type></entry>
5167       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
5168       <entry>Input conversion function (binary format), or 0 if none</entry>
5169      </row>
5170
5171      <row>
5172       <entry><structfield>typsend</structfield></entry>
5173       <entry><type>regproc</type></entry>
5174       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
5175       <entry>Output conversion function (binary format), or 0 if none</entry>
5176      </row>
5177
5178      <row>
5179       <entry><structfield>typmodin</structfield></entry>
5180       <entry><type>regproc</type></entry>
5181       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
5182       <entry>Type modifier input function, or 0 if type does not support modifiers</entry>
5183      </row>
5184
5185      <row>
5186       <entry><structfield>typmodout</structfield></entry>
5187       <entry><type>regproc</type></entry>
5188       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
5189       <entry>Type modifier output function, or 0 to use the standard format</entry>
5190      </row>
5191
5192      <row>
5193       <entry><structfield>typanalyze</structfield></entry>
5194       <entry><type>regproc</type></entry>
5195       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
5196       <entry>Custom ANALYZE function, or 0 to use the standard function</entry>
5197      </row>
5198
5199      <row>
5200       <entry><structfield>typalign</structfield></entry>
5201       <entry><type>char</type></entry>
5202       <entry></entry>
5203       <entry><para>
5204
5205        <structfield>typalign</structfield> is the alignment required
5206        when storing a value of this type.  It applies to storage on
5207        disk as well as most representations of the value inside
5208        <productname>PostgreSQL</>.
5209        When multiple values are stored consecutively, such
5210        as in the representation of a complete row on disk, padding is
5211        inserted before a datum of this type so that it begins on the
5212        specified boundary.  The alignment reference is the beginning
5213        of the first datum in the sequence.
5214       </para><para>
5215        Possible values are:
5216        <itemizedlist>
5217         <listitem>
5218          <para><literal>c</> = <type>char</type> alignment, i.e., no alignment needed.</para>
5219         </listitem>
5220         <listitem>
5221          <para><literal>s</> = <type>short</type> alignment (2 bytes on most machines).</para>
5222         </listitem>
5223         <listitem>
5224          <para><literal>i</> = <type>int</type> alignment (4 bytes on most machines).</para>
5225         </listitem>
5226         <listitem>
5227          <para><literal>d</> = <type>double</type> alignment (8 bytes on many machines, but by no means all).</para>
5228         </listitem>
5229        </itemizedlist>
5230       </para><note>
5231        <para>
5232         For types used in system tables, it is critical that the size
5233         and alignment defined in <structname>pg_type</structname>
5234         agree with the way that the compiler will lay out the column in
5235         a structure representing a table row.
5236        </para>
5237       </note></entry>
5238      </row>
5239
5240      <row>
5241       <entry><structfield>typstorage</structfield></entry>
5242       <entry><type>char</type></entry>
5243       <entry></entry>
5244       <entry><para>
5245        <structfield>typstorage</structfield> tells for varlena
5246        types (those with <structfield>typlen</structfield> = -1) if
5247        the type is prepared for toasting and what the default strategy
5248        for attributes of this type should be.
5249        Possible values are
5250        <itemizedlist>
5251         <listitem>
5252          <para><literal>p</>: Value must always be stored plain.</para>
5253         </listitem>
5254         <listitem>
5255          <para>
5256           <literal>e</>: Value can be stored in a <quote>secondary</quote>
5257           relation (if relation has one, see
5258           <literal>pg_class.reltoastrelid</literal>).
5259          </para>
5260         </listitem>
5261         <listitem>
5262          <para><literal>m</>: Value can be stored compressed inline.</para>
5263         </listitem>
5264         <listitem>
5265          <para><literal>x</>: Value can be stored compressed inline or stored in <quote>secondary</quote> storage.</para>
5266         </listitem>
5267        </itemizedlist>
5268        Note that <literal>m</> columns can also be moved out to secondary
5269        storage, but only as a last resort (<literal>e</> and <literal>x</> columns are
5270        moved first).
5271       </para></entry>
5272      </row>
5273
5274      <row>
5275       <entry><structfield>typnotnull</structfield></entry>
5276       <entry><type>bool</type></entry>
5277       <entry></entry>
5278       <entry><para>
5279        <structfield>typnotnull</structfield> represents a not-null
5280        constraint on a type.  Used for domains only
5281       </para></entry>
5282      </row>
5283
5284      <row>
5285       <entry><structfield>typbasetype</structfield></entry>
5286       <entry><type>oid</type></entry>
5287       <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
5288       <entry><para>
5289        If this is a domain (see <structfield>typtype</structfield>), then
5290        <structfield>typbasetype</structfield> identifies the type that this
5291        one is based on.  Zero if this type is not a domain
5292       </para></entry>
5293      </row>
5294
5295      <row>
5296       <entry><structfield>typtypmod</structfield></entry>
5297       <entry><type>int4</type></entry>
5298       <entry></entry>
5299       <entry><para>
5300        Domains use <structfield>typtypmod</structfield> to record the <literal>typmod</>
5301        to be applied to their base type (-1 if base type does not use a
5302        <literal>typmod</>).  -1 if this type is not a domain
5303       </para></entry>
5304      </row>
5305
5306      <row>
5307       <entry><structfield>typndims</structfield></entry>
5308       <entry><type>int4</type></entry>
5309       <entry></entry>
5310       <entry><para>
5311        <structfield>typndims</structfield> is the number of array dimensions
5312        for a domain that is an array (that is, <structfield>typbasetype</> is
5313        an array type; the domain's <structfield>typelem</> will match the base
5314        type's <structfield>typelem</structfield>).
5315        Zero for types other than domains over array types
5316        </para></entry>
5317      </row>
5318
5319      <row>
5320       <entry><structfield>typdefaultbin</structfield></entry>
5321       <entry><type>text</type></entry>
5322       <entry></entry>
5323       <entry><para>
5324        If <structfield>typdefaultbin</> is not null, it is the <function>nodeToString()</function>
5325        representation of a default expression for the type.  This is
5326        only used for domains
5327       </para></entry>
5328      </row>
5329
5330      <row>
5331       <entry><structfield>typdefault</structfield></entry>
5332       <entry><type>text</type></entry>
5333       <entry></entry>
5334       <entry><para>
5335        <structfield>typdefault</> is null if the type has no associated
5336        default value. If <structfield>typdefaultbin</> is not null,
5337        <structfield>typdefault</> must contain a human-readable version of the
5338        default expression represented by <structfield>typdefaultbin</>.  If
5339        <structfield>typdefaultbin</> is null and <structfield>typdefault</> is
5340        not, then <structfield>typdefault</> is the external representation of
5341        the type's default value, which might be fed to the type's input
5342        converter to produce a constant
5343       </para></entry>
5344      </row>
5345     </tbody>
5346    </tgroup>
5347   </table>
5348
5349   <para>
5350    <xref linkend="catalog-typcategory-table"> lists the system-defined values
5351    of <structfield>typcategory</>.  Any future additions to this list will
5352    also be upper-case ASCII letters.  All other ASCII characters are reserved
5353    for user-defined categories.
5354   </para>
5355
5356   <table id="catalog-typcategory-table">
5357    <title><structfield>typcategory</> Codes</title>
5358
5359    <tgroup cols="2">
5360     <thead>
5361      <row>
5362       <entry>Code</entry>
5363       <entry>Category</entry>
5364      </row>
5365     </thead>
5366
5367     <tbody>
5368      <row>
5369       <entry><literal>A</literal></entry>
5370       <entry>Array types</entry>
5371      </row>
5372      <row>
5373       <entry><literal>B</literal></entry>
5374       <entry>Boolean types</entry>
5375      </row>
5376      <row>
5377       <entry><literal>C</literal></entry>
5378       <entry>Composite types</entry>
5379      </row>
5380      <row>
5381       <entry><literal>D</literal></entry>
5382       <entry>Date/time types</entry>
5383      </row>
5384      <row>
5385       <entry><literal>E</literal></entry>
5386       <entry>Enum types</entry>
5387      </row>
5388      <row>
5389       <entry><literal>G</literal></entry>
5390       <entry>Geometric types</entry>
5391      </row>
5392      <row>
5393       <entry><literal>I</literal></entry>
5394       <entry>Network address types</entry>
5395      </row>
5396      <row>
5397       <entry><literal>N</literal></entry>
5398       <entry>Numeric types</entry>
5399      </row>
5400      <row>
5401       <entry><literal>P</literal></entry>
5402       <entry>Pseudo-types</entry>
5403      </row>
5404      <row>
5405       <entry><literal>S</literal></entry>
5406       <entry>String types</entry>
5407      </row>
5408      <row>
5409       <entry><literal>T</literal></entry>
5410       <entry>Timespan types</entry>
5411      </row>
5412      <row>
5413       <entry><literal>U</literal></entry>
5414       <entry>User-defined types</entry>
5415      </row>
5416      <row>
5417       <entry><literal>V</literal></entry>
5418       <entry>Bit-string types</entry>
5419      </row>
5420      <row>
5421       <entry><literal>X</literal></entry>
5422       <entry><type>unknown</> type</entry>
5423      </row>
5424     </tbody>
5425    </tgroup>
5426   </table>
5427
5428  </sect1>
5429
5430
5431  <sect1 id="catalog-pg-user-mapping">
5432   <title><structname>pg_user_mapping</structname></title>
5433
5434   <indexterm zone="catalog-pg-user-mapping">
5435    <primary>pg_user_mapping</primary>
5436   </indexterm>
5437
5438   <para>
5439    The catalog <structname>pg_user_mapping</structname> stores
5440    the mappings from local user to remote.  Access to this catalog is
5441    restricted from normal users, use the view
5442    <link linkend="view-pg-user-mappings"><structname>pg_user_mappings</structname></link>
5443    instead.
5444   </para>
5445
5446   <table>
5447    <title><structname>pg_user_mapping</> Columns</title>
5448
5449    <tgroup cols="4">
5450     <thead>
5451      <row>
5452       <entry>Name</entry>
5453       <entry>Type</entry>
5454       <entry>References</entry>
5455       <entry>Description</entry>
5456      </row>
5457     </thead>
5458
5459     <tbody>
5460      <row>
5461       <entry><structfield>umuser</structfield></entry>
5462       <entry><type>oid</type></entry>
5463       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
5464       <entry>OID of the local role being mapped, 0 if the user mapping is public</entry>
5465      </row>
5466
5467      <row>
5468       <entry><structfield>umserver</structfield></entry>
5469       <entry><type>oid</type></entry>
5470       <entry><literal><link linkend="catalog-pg-foreign-server"><structname>pg_foreign_server</structname></link>.oid</literal></entry>
5471       <entry>
5472        The OID of the foreign server that contains this mapping
5473       </entry>
5474      </row>
5475
5476      <row>
5477       <entry><structfield>umoptions</structfield></entry>
5478       <entry><type>text[]</type></entry>
5479       <entry></entry>
5480       <entry>
5481        User mapping specific options, as <quote>keyword=value</> strings.
5482       </entry>
5483      </row>
5484     </tbody>
5485    </tgroup>
5486   </table>
5487  </sect1>
5488
5489
5490  <sect1 id="views-overview">
5491   <title>System Views</title>
5492
5493   <para>
5494    In addition to the system catalogs, <productname>PostgreSQL</productname>
5495    provides a number of built-in views.  Some system views provide convenient
5496    access to some commonly used queries on the system catalogs.  Other views
5497    provide access to internal server state.
5498   </para>
5499
5500   <para>
5501    The information schema (<xref linkend="information-schema">) provides
5502    an alternative set of views which overlap the functionality of the system
5503    views.  Since the information schema is SQL-standard whereas the views
5504    described here are <productname>PostgreSQL</productname>-specific,
5505    it's usually better to use the information schema if it provides all
5506    the information you need.
5507   </para>
5508
5509   <para>
5510    <xref linkend="view-table"> lists the system views described here.
5511    More detailed documentation of each view follows below.
5512    There are some additional views that provide access to the results of
5513    the statistics collector; they are described in <xref
5514    linkend="monitoring-stats-views-table">.
5515   </para>
5516
5517   <para>
5518    Except where noted, all the views described here are read-only.
5519   </para>
5520
5521   <table id="view-table">
5522    <title>System Views</title>
5523
5524    <tgroup cols="2">
5525     <thead>
5526      <row>
5527       <entry>View Name</entry>
5528       <entry>Purpose</entry>
5529      </row>
5530     </thead>
5531
5532     <tbody>
5533      <row>
5534       <entry><link linkend="view-pg-cursors"><structname>pg_cursors</structname></link></entry>
5535       <entry>open cursors</entry>
5536      </row>
5537
5538      <row>
5539       <entry><link linkend="view-pg-group"><structname>pg_group</structname></link></entry>
5540       <entry>groups of database users</entry>
5541      </row>
5542
5543      <row>
5544       <entry><link linkend="view-pg-indexes"><structname>pg_indexes</structname></link></entry>
5545       <entry>indexes</entry>
5546      </row>
5547
5548      <row>
5549       <entry><link linkend="view-pg-locks"><structname>pg_locks</structname></link></entry>
5550       <entry>currently held locks</entry>
5551      </row>
5552
5553      <row>
5554       <entry><link linkend="view-pg-prepared-statements"><structname>pg_prepared_statements</structname></link></entry>
5555       <entry>prepared statements</entry>
5556      </row>
5557
5558      <row>
5559       <entry><link linkend="view-pg-prepared-xacts"><structname>pg_prepared_xacts</structname></link></entry>
5560       <entry>prepared transactions</entry>
5561      </row>
5562
5563      <row>
5564       <entry><link linkend="view-pg-roles"><structname>pg_roles</structname></link></entry>
5565       <entry>database roles</entry>
5566      </row>
5567
5568      <row>
5569       <entry><link linkend="view-pg-rules"><structname>pg_rules</structname></link></entry>
5570       <entry>rules</entry>
5571      </row>
5572
5573      <row>
5574       <entry><link linkend="view-pg-settings"><structname>pg_settings</structname></link></entry>
5575       <entry>parameter settings</entry>
5576      </row>
5577
5578      <row>
5579       <entry><link linkend="view-pg-shadow"><structname>pg_shadow</structname></link></entry>
5580       <entry>database users</entry>
5581      </row>
5582
5583      <row>
5584       <entry><link linkend="view-pg-stats"><structname>pg_stats</structname></link></entry>
5585       <entry>planner statistics</entry>
5586      </row>
5587
5588      <row>
5589       <entry><link linkend="view-pg-tables"><structname>pg_tables</structname></link></entry>
5590       <entry>tables</entry>
5591      </row>
5592
5593      <row>
5594       <entry><link linkend="view-pg-timezone-abbrevs"><structname>pg_timezone_abbrevs</structname></link></entry>
5595       <entry>time zone abbreviations</entry>
5596      </row>
5597
5598      <row>
5599       <entry><link linkend="view-pg-timezone-names"><structname>pg_timezone_names</structname></link></entry>
5600       <entry>time zone names</entry>
5601      </row>
5602
5603      <row>
5604       <entry><link linkend="view-pg-user"><structname>pg_user</structname></link></entry>
5605       <entry>database users</entry>
5606      </row>
5607
5608      <row>
5609       <entry><link linkend="view-pg-views"><structname>pg_views</structname></link></entry>
5610       <entry>views</entry>
5611      </row>
5612
5613     </tbody>
5614    </tgroup>
5615   </table>
5616  </sect1>
5617
5618  <sect1 id="view-pg-cursors">
5619   <title><structname>pg_cursors</structname></title>
5620
5621   <indexterm zone="view-pg-cursors">
5622    <primary>pg_cursors</primary>
5623   </indexterm>
5624
5625   <para>
5626    The <structname>pg_cursors</structname> view lists the cursors that
5627    are currently available. Cursors can be defined in several ways:
5628    <itemizedlist>
5629     <listitem>
5630      <para>
5631       via the <xref linkend="sql-declare" endterm="sql-declare-title">
5632       statement in SQL
5633      </para>
5634     </listitem>
5635
5636     <listitem>
5637      <para>
5638       via the Bind message in the frontend/backend protocol, as
5639       described in <xref linkend="protocol-flow-ext-query">
5640      </para>
5641     </listitem>
5642
5643     <listitem>
5644      <para>
5645       via the Server Programming Interface (SPI), as described in
5646       <xref linkend="spi-interface">
5647      </para>
5648     </listitem>
5649    </itemizedlist>
5650
5651    The <structname>pg_cursors</structname> view displays cursors
5652    created by any of these means. Cursors only exist for the duration
5653    of the transaction that defines them, unless they have been
5654    declared <literal>WITH HOLD</literal>. Therefore non-holdable
5655    cursors are only present in the view until the end of their
5656    creating transaction.
5657
5658    <note>
5659     <para>
5660      Cursors are used internally to implement some of the components
5661      of <productname>PostgreSQL</>, such as procedural languages.
5662      Therefore, the <structname>pg_cursors</> view might include cursors
5663      that have not been explicitly created by the user.
5664     </para>
5665    </note>
5666   </para>
5667
5668   <table>
5669    <title><structname>pg_cursors</> Columns</title>
5670
5671    <tgroup cols="3">
5672     <thead>
5673      <row>
5674       <entry>Name</entry>
5675       <entry>Type</entry>
5676       <entry>Description</entry>
5677      </row>
5678     </thead>
5679
5680     <tbody>
5681      <row>
5682       <entry><structfield>name</structfield></entry>
5683       <entry><type>text</type></entry>
5684       <entry>The name of the cursor</entry>
5685      </row>
5686
5687      <row>
5688       <entry><structfield>statement</structfield></entry>
5689       <entry><type>text</type></entry>
5690       <entry>The verbatim query string submitted to declare this cursor</entry>
5691      </row>
5692
5693      <row>
5694       <entry><structfield>is_holdable</structfield></entry>
5695       <entry><type>boolean</type></entry>
5696       <entry>
5697        <literal>true</literal> if the cursor is holdable (that is, it
5698        can be accessed after the transaction that declared the cursor
5699        has committed); <literal>false</literal> otherwise
5700        </entry>
5701      </row>
5702
5703      <row>
5704       <entry><structfield>is_binary</structfield></entry>
5705       <entry><type>boolean</type></entry>
5706       <entry>
5707        <literal>true</literal> if the cursor was declared
5708        <literal>BINARY</literal>; <literal>false</literal>
5709        otherwise
5710        </entry>
5711      </row>
5712
5713      <row>
5714       <entry><structfield>is_scrollable</structfield></entry>
5715       <entry><type>boolean</type></entry>
5716       <entry>
5717        <literal>true</> if the cursor is scrollable (that is, it
5718        allows rows to be retrieved in a nonsequential manner);
5719        <literal>false</literal> otherwise
5720        </entry>
5721      </row>
5722
5723      <row>
5724       <entry><structfield>creation_time</structfield></entry>
5725       <entry><type>timestamptz</type></entry>
5726       <entry>The time at which the cursor was declared</entry>
5727      </row>
5728     </tbody>
5729    </tgroup>
5730   </table>
5731
5732   <para>
5733    The <structname>pg_cursors</structname> view is read only.
5734   </para>
5735
5736  </sect1>
5737
5738  <sect1 id="view-pg-group">
5739   <title><structname>pg_group</structname></title>
5740
5741   <indexterm zone="view-pg-group">
5742    <primary>pg_group</primary>
5743   </indexterm>
5744
5745   <para>
5746    The view <structname>pg_group</structname> exists for backwards
5747    compatibility: it emulates a catalog that existed in
5748    <productname>PostgreSQL</productname> before version 8.1.
5749    It shows the names and members of all roles that are marked as not
5750    <structfield>rolcanlogin</>, which is an approximation to the set
5751    of roles that are being used as groups.
5752   </para>
5753
5754   <table>
5755    <title><structname>pg_group</> Columns</title>
5756
5757    <tgroup cols="4">
5758     <thead>
5759      <row>
5760       <entry>Name</entry>
5761       <entry>Type</entry>
5762       <entry>References</entry>
5763       <entry>Description</entry>
5764      </row>
5765     </thead>
5766
5767     <tbody>
5768      <row>
5769       <entry><structfield>groname</structfield></entry>
5770       <entry><type>name</type></entry>
5771       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.rolname</literal></entry>
5772       <entry>Name of the group</entry>
5773      </row>
5774
5775      <row>
5776       <entry><structfield>grosysid</structfield></entry>
5777       <entry><type>oid</type></entry>
5778       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
5779       <entry>ID of this group</entry>
5780      </row>
5781
5782      <row>
5783       <entry><structfield>grolist</structfield></entry>
5784       <entry><type>oid[]</type></entry>
5785       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
5786       <entry>An array containing the IDs of the roles in this group</entry>
5787      </row>
5788     </tbody>
5789    </tgroup>
5790   </table>
5791
5792  </sect1>
5793
5794  <sect1 id="view-pg-indexes">
5795   <title><structname>pg_indexes</structname></title>
5796
5797   <indexterm zone="view-pg-indexes">
5798    <primary>pg_indexes</primary>
5799   </indexterm>
5800
5801   <para>
5802    The view <structname>pg_indexes</structname> provides access to
5803    useful information about each index in the database.
5804   </para>
5805
5806   <table>
5807    <title><structname>pg_indexes</> Columns</title>
5808
5809    <tgroup cols="4">
5810     <thead>
5811      <row>
5812       <entry>Name</entry>
5813       <entry>Type</entry>
5814       <entry>References</entry>
5815       <entry>Description</entry>
5816      </row>
5817     </thead>
5818     <tbody>
5819      <row>
5820       <entry><structfield>schemaname</structfield></entry>
5821       <entry><type>name</type></entry>
5822       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.nspname</literal></entry>
5823       <entry>Name of schema containing table and index</entry>
5824      </row>
5825      <row>
5826       <entry><structfield>tablename</structfield></entry>
5827       <entry><type>name</type></entry>
5828       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.relname</literal></entry>
5829       <entry>Name of table the index is for</entry>
5830      </row>
5831      <row>
5832       <entry><structfield>indexname</structfield></entry>
5833       <entry><type>name</type></entry>
5834       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.relname</literal></entry>
5835       <entry>Name of index</entry>
5836      </row>
5837      <row>
5838       <entry><structfield>tablespace</structfield></entry>
5839       <entry><type>name</type></entry>
5840       <entry><literal><link linkend="catalog-pg-tablespace"><structname>pg_tablespace</structname></link>.spcname</literal></entry>
5841       <entry>Name of tablespace containing index (NULL if default for database)</entry>
5842      </row>
5843      <row>
5844       <entry><structfield>indexdef</structfield></entry>
5845       <entry><type>text</type></entry>
5846       <entry></entry>
5847       <entry>Index definition (a reconstructed <command>CREATE INDEX</command>
5848       command)</entry>
5849      </row>
5850     </tbody>
5851    </tgroup>
5852   </table>
5853
5854  </sect1>
5855
5856  <sect1 id="view-pg-locks">
5857   <title><structname>pg_locks</structname></title>
5858
5859   <indexterm zone="view-pg-locks">
5860    <primary>pg_locks</primary>
5861   </indexterm>
5862
5863   <para>
5864    The view <structname>pg_locks</structname> provides access to
5865    information about the locks held by open transactions within the
5866    database server.  See <xref linkend="mvcc"> for more discussion
5867    of locking.
5868   </para>
5869
5870   <para>
5871    <structname>pg_locks</structname> contains one row per active lockable
5872    object, requested lock mode, and relevant transaction.  Thus, the same
5873    lockable object might
5874    appear many times, if multiple transactions are holding or waiting
5875    for locks on it.  However, an object that currently has no locks on it
5876    will not appear at all.
5877   </para>
5878
5879   <para>
5880    There are several distinct types of lockable objects:
5881    whole relations (e.g., tables), individual pages of relations,
5882    individual tuples of relations,
5883    transaction IDs (both virtual and permanent IDs),
5884    and general database objects (identified by class OID and object OID,
5885    in the same way as in <structname>pg_description</structname> or
5886    <structname>pg_depend</structname>).  Also, the right to extend a
5887    relation is represented as a separate lockable object.
5888   </para>
5889
5890   <table>
5891    <title><structname>pg_locks</> Columns</title>
5892
5893    <tgroup cols="4">
5894     <thead>
5895      <row>
5896       <entry>Name</entry>
5897       <entry>Type</entry>
5898       <entry>References</entry>
5899       <entry>Description</entry>
5900      </row>
5901     </thead>
5902     <tbody>
5903      <row>
5904       <entry><structfield>locktype</structfield></entry>
5905       <entry><type>text</type></entry>
5906       <entry></entry>
5907       <entry>
5908        type of the lockable object:
5909        <literal>relation</>,
5910        <literal>extend</>,
5911        <literal>page</>,
5912        <literal>tuple</>,
5913        <literal>transactionid</>,
5914        <literal>virtualxid</>,
5915        <literal>object</>,
5916        <literal>userlock</>, or
5917        <literal>advisory</>
5918       </entry>
5919      </row>
5920      <row>
5921       <entry><structfield>database</structfield></entry>
5922       <entry><type>oid</type></entry>
5923       <entry><literal><link linkend="catalog-pg-database"><structname>pg_database</structname></link>.oid</literal></entry>
5924       <entry>
5925        OID of the database in which the object exists, or
5926        zero if the object is a shared object, or
5927        NULL if the object is a transaction ID
5928       </entry>
5929      </row>
5930      <row>
5931       <entry><structfield>relation</structfield></entry>
5932       <entry><type>oid</type></entry>
5933       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
5934       <entry>
5935        OID of the relation, or NULL if the object is not
5936        a relation or part of a relation
5937       </entry>
5938      </row>
5939      <row>
5940       <entry><structfield>page</structfield></entry>
5941       <entry><type>integer</type></entry>
5942       <entry></entry>
5943       <entry>
5944        Page number within the relation, or NULL if the object
5945        is not a tuple or relation page
5946       </entry>
5947      </row>
5948      <row>
5949       <entry><structfield>tuple</structfield></entry>
5950       <entry><type>smallint</type></entry>
5951       <entry></entry>
5952       <entry>
5953        Tuple number within the page, or NULL if the object is not a tuple
5954       </entry>
5955      </row>
5956      <row>
5957       <entry><structfield>virtualxid</structfield></entry>
5958       <entry><type>text</type></entry>
5959       <entry></entry>
5960       <entry>
5961        Virtual ID of a transaction, or NULL if the object is not a
5962        virtual transaction ID
5963       </entry>
5964      </row>
5965      <row>
5966       <entry><structfield>transactionid</structfield></entry>
5967       <entry><type>xid</type></entry>
5968       <entry></entry>
5969       <entry>
5970        ID of a transaction, or NULL if the object is not a transaction ID
5971       </entry>
5972      </row>
5973      <row>
5974       <entry><structfield>classid</structfield></entry>
5975       <entry><type>oid</type></entry>
5976       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
5977       <entry>
5978        OID of the system catalog containing the object, or NULL if the
5979        object is not a general database object
5980       </entry>
5981      </row>
5982      <row>
5983       <entry><structfield>objid</structfield></entry>
5984       <entry><type>oid</type></entry>
5985       <entry>any OID column</entry>
5986       <entry>
5987        OID of the object within its system catalog, or NULL if the
5988        object is not a general database object.
5989        For advisory locks it is used to distinguish the two key
5990        spaces (<literal>1</> for an int8 key, <literal>2</> for two
5991        int4 keys).
5992       </entry>
5993      </row>
5994      <row>
5995       <entry><structfield>objsubid</structfield></entry>
5996       <entry><type>smallint</type></entry>
5997       <entry></entry>
5998       <entry>
5999        For a table column, this is the column number (the
6000        <structfield>classid</> and <structfield>objid</> refer to the
6001        table itself).  For all other object types, this column is
6002        zero.  NULL if the object is not a general database object
6003       </entry>
6004      </row>
6005      <row>
6006       <entry><structfield>virtualtransaction</structfield></entry>
6007       <entry><type>text</type></entry>
6008       <entry></entry>
6009       <entry>
6010        Virtual ID of the transaction that is holding or awaiting this lock
6011       </entry>
6012      </row>
6013      <row>
6014       <entry><structfield>pid</structfield></entry>
6015       <entry><type>integer</type></entry>
6016       <entry></entry>
6017       <entry>
6018        Process ID of the server process holding or awaiting this
6019        lock.  NULL if the lock is held by a prepared transaction
6020       </entry>
6021      </row>
6022      <row>
6023       <entry><structfield>mode</structfield></entry>
6024       <entry><type>text</type></entry>
6025       <entry></entry>
6026       <entry>Name of the lock mode held or desired by this process (see <xref
6027       linkend="locking-tables">)</entry>
6028      </row>
6029      <row>
6030       <entry><structfield>granted</structfield></entry>
6031       <entry><type>boolean</type></entry>
6032       <entry></entry>
6033       <entry>True if lock is held, false if lock is awaited</entry>
6034      </row>
6035     </tbody>
6036    </tgroup>
6037   </table>
6038
6039   <para>
6040    <structfield>granted</structfield> is true in a row representing a lock
6041    held by the indicated transaction.  False indicates that this transaction is
6042    currently waiting to acquire this lock, which implies that some other
6043    transaction is holding a conflicting lock mode on the same lockable object.
6044    The waiting transaction will sleep until the other lock is released (or a
6045    deadlock situation is detected). A single transaction can be waiting to
6046    acquire at most one lock at a time.
6047   </para>
6048
6049   <para>
6050    Every transaction holds an exclusive lock on its virtual transaction ID for
6051    its entire duration.  If a permanent ID is assigned to the transaction
6052    (which normally happens only if the transaction changes the state of the
6053    database), it also holds an exclusive lock on its permanent transaction ID
6054    until it ends.  When one transaction finds it necessary to wait specifically
6055    for another transaction, it does so by attempting to acquire share lock on
6056    the other transaction ID (either virtual or permanent ID depending on the
6057    situation). That will succeed only when the other transaction
6058    terminates and releases its locks.
6059   </para>
6060
6061   <para>
6062    Although tuples are a lockable type of object,
6063    information about row-level locks is stored on disk, not in memory,
6064    and therefore row-level locks normally do not appear in this view.
6065    If a transaction is waiting for a
6066    row-level lock, it will usually appear in the view as waiting for the
6067    permanent transaction ID of the current holder of that row lock.
6068   </para>
6069
6070   <para>
6071    Advisory locks can be acquired on keys consisting of either a single
6072    <type>bigint</type> value or two integer values.  A <type>bigint</type> key is displayed with its
6073    high-order half in the <structfield>classid</> column, its low-order half
6074    in the <structfield>objid</> column, and <structfield>objsubid</> equal
6075    to 1.  Integer keys are displayed with the first key in the
6076    <structfield>classid</> column, the second key in the <structfield>objid</>
6077    column, and <structfield>objsubid</> equal to 2.  The actual meaning of
6078    the keys is up to the user.  Advisory locks are local to each database,
6079    so the <structfield>database</> column is meaningful for an advisory lock.
6080   </para>
6081
6082   <para>
6083    When the <structname>pg_locks</structname> view is accessed, the
6084    internal lock manager data structures are momentarily locked, and
6085    a copy is made for the view to display.  This ensures that the
6086    view produces a consistent set of results, while not blocking
6087    normal lock manager operations longer than necessary.  Nonetheless
6088    there could be some impact on database performance if this view is
6089    frequently accessed.
6090   </para>
6091
6092   <para>
6093    <structname>pg_locks</structname> provides a global view of all locks
6094    in the database cluster, not only those relevant to the current database.
6095    Although its <structfield>relation</structfield> column can be joined
6096    against <structname>pg_class</>.<structfield>oid</> to identify locked
6097    relations, this will only work correctly for relations in the current
6098    database (those for which the <structfield>database</structfield> column
6099    is either the current database's OID or zero).
6100   </para>
6101
6102   <para>
6103    The <structfield>pid</structfield> column can be joined to the
6104    <structfield>procpid</structfield> column of the
6105    <structname>pg_stat_activity</structname> view to get more
6106    information on the session holding or waiting to hold each lock.
6107    Also, if you are using prepared transactions, the
6108    <structfield>transaction</> column can be joined to the
6109    <structfield>transaction</structfield> column of the
6110    <structname>pg_prepared_xacts</structname> view to get more
6111    information on prepared transactions that hold locks.
6112    (A prepared transaction can never be waiting for a lock,
6113    but it continues to hold the locks it acquired while running.)
6114   </para>
6115
6116  </sect1>
6117
6118  <sect1 id="view-pg-prepared-statements">
6119   <title><structname>pg_prepared_statements</structname></title>
6120
6121   <indexterm zone="view-pg-prepared-statements">
6122    <primary>pg_prepared_statements</primary>
6123   </indexterm>
6124
6125   <para>
6126    The <structname>pg_prepared_statements</structname> view displays
6127    all the prepared statements that are available in the current
6128    session. See <xref linkend="sql-prepare"
6129    endterm="sql-prepare-title"> for more information about prepared
6130    statements.
6131   </para>
6132
6133   <para>
6134    <structname>pg_prepared_statements</structname> contains one row
6135    for each prepared statement. Rows are added to the view when a new
6136    prepared statement is created and removed when a prepared statement
6137    is released (for example, via the <xref linkend="sql-deallocate"
6138    endterm="sql-deallocate-title"> command).
6139   </para>
6140
6141   <table>
6142    <title><structname>pg_prepared_statements</> Columns</title>
6143
6144    <tgroup cols="3">
6145     <thead>
6146      <row>
6147       <entry>Name</entry>
6148       <entry>Type</entry>
6149       <entry>Description</entry>
6150      </row>
6151     </thead>
6152     <tbody>
6153      <row>
6154       <entry><structfield>name</structfield></entry>
6155       <entry><type>text</type></entry>
6156       <entry>
6157        The identifier of the prepared statement
6158       </entry>
6159      </row>
6160      <row>
6161       <entry><structfield>statement</structfield></entry>
6162       <entry><type>text</type></entry>
6163       <entry>
6164        The query string submitted by the client to create this
6165        prepared statement. For prepared statements created via SQL,
6166        this is the <command>PREPARE</command> statement submitted by
6167        the client. For prepared statements created via the
6168        frontend/backend protocol, this is the text of the prepared
6169        statement itself
6170       </entry>
6171      </row>
6172      <row>
6173       <entry><structfield>prepare_time</structfield></entry>
6174       <entry><type>timestamptz</type></entry>
6175       <entry>
6176        The time at which the prepared statement was created
6177       </entry>
6178      </row>
6179      <row>
6180       <entry><structfield>parameter_types</structfield></entry>
6181       <entry><type>regtype[]</type></entry>
6182       <entry>
6183        The expected parameter types for the prepared statement in the
6184        form of an array of <type>regtype</type>. The OID corresponding
6185        to an element of this array can be obtained by casting the
6186        <type>regtype</type> value to <type>oid</type>
6187       </entry>
6188      </row>
6189      <row>
6190       <entry><structfield>from_sql</structfield></entry>
6191       <entry><type>boolean</type></entry>
6192       <entry>
6193        <literal>true</literal> if the prepared statement was created
6194        via the <command>PREPARE</command> SQL statement;
6195        <literal>false</literal> if the statement was prepared via the
6196        frontend/backend protocol
6197       </entry>
6198      </row>
6199     </tbody>
6200    </tgroup>
6201   </table>
6202
6203   <para>
6204    The <structname>pg_prepared_statements</structname> view is read only.
6205   </para>
6206  </sect1>
6207
6208  <sect1 id="view-pg-prepared-xacts">
6209   <title><structname>pg_prepared_xacts</structname></title>
6210
6211   <indexterm zone="view-pg-prepared-xacts">
6212    <primary>pg_prepared_xacts</primary>
6213   </indexterm>
6214
6215   <para>
6216    The view <structname>pg_prepared_xacts</structname> displays
6217    information about transactions that are currently prepared for two-phase
6218    commit (see <xref linkend="sql-prepare-transaction"
6219    endterm="sql-prepare-transaction-title"> for details).
6220   </para>
6221
6222   <para>
6223    <structname>pg_prepared_xacts</structname> contains one row per prepared
6224    transaction.  An entry is removed when the transaction is committed or
6225    rolled back.
6226   </para>
6227
6228   <table>
6229    <title><structname>pg_prepared_xacts</> Columns</title>
6230
6231    <tgroup cols="4">
6232     <thead>
6233      <row>
6234       <entry>Name</entry>
6235       <entry>Type</entry>
6236       <entry>References</entry>
6237       <entry>Description</entry>
6238      </row>
6239     </thead>
6240     <tbody>
6241      <row>
6242       <entry><structfield>transaction</structfield></entry>
6243       <entry><type>xid</type></entry>
6244       <entry></entry>
6245       <entry>
6246        Numeric transaction identifier of the prepared transaction
6247       </entry>
6248      </row>
6249      <row>
6250       <entry><structfield>gid</structfield></entry>
6251       <entry><type>text</type></entry>
6252       <entry></entry>
6253       <entry>
6254        Global transaction identifier that was assigned to the transaction
6255       </entry>
6256      </row>
6257      <row>
6258       <entry><structfield>prepared</structfield></entry>
6259       <entry><type>timestamp with time zone</type></entry>
6260       <entry></entry>
6261       <entry>
6262        Time at which the transaction was prepared for commit
6263       </entry>
6264      </row>
6265      <row>
6266       <entry><structfield>owner</structfield></entry>
6267       <entry><type>name</type></entry>
6268       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.rolname</literal></entry>
6269       <entry>
6270        Name of the user that executed the transaction
6271       </entry>
6272      </row>
6273      <row>
6274       <entry><structfield>database</structfield></entry>
6275       <entry><type>name</type></entry>
6276       <entry><literal><link linkend="catalog-pg-database"><structname>pg_database</structname></link>.datname</literal></entry>
6277       <entry>
6278        Name of the database in which the transaction was executed
6279       </entry>
6280      </row>
6281     </tbody>
6282    </tgroup>
6283   </table>
6284
6285   <para>
6286    When the <structname>pg_prepared_xacts</structname> view is accessed, the
6287    internal transaction manager data structures are momentarily locked, and
6288    a copy is made for the view to display.  This ensures that the
6289    view produces a consistent set of results, while not blocking
6290    normal operations longer than necessary.  Nonetheless
6291    there could be some impact on database performance if this view is
6292    frequently accessed.
6293   </para>
6294
6295  </sect1>
6296
6297  <sect1 id="view-pg-roles">
6298   <title><structname>pg_roles</structname></title>
6299
6300   <indexterm zone="view-pg-roles">
6301    <primary>pg_roles</primary>
6302   </indexterm>
6303
6304   <para>
6305    The view <structname>pg_roles</structname> provides access to
6306    information about database roles.  This is simply a publicly
6307    readable view of
6308    <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>
6309    that blanks out the password field.
6310   </para>
6311
6312   <para>
6313    This view explicitly exposes the OID column of the underlying table,
6314    since that is needed to do joins to other catalogs.
6315   </para>
6316
6317   <table>
6318    <title><structname>pg_roles</> Columns</title>
6319
6320    <tgroup cols="4">
6321     <thead>
6322      <row>
6323       <entry>Name</entry>
6324       <entry>Type</entry>
6325       <entry>References</entry>
6326       <entry>Description</entry>
6327      </row>
6328     </thead>
6329
6330     <tbody>
6331      <row>
6332       <entry><structfield>rolname</structfield></entry>
6333       <entry><type>name</type></entry>
6334       <entry></entry>
6335       <entry>Role name</entry>
6336      </row>
6337
6338      <row>
6339       <entry><structfield>rolsuper</structfield></entry>
6340       <entry><type>bool</type></entry>
6341       <entry></entry>
6342       <entry>Role has superuser privileges</entry>
6343      </row>
6344
6345      <row>
6346       <entry><structfield>rolinherit</structfield></entry>
6347       <entry><type>bool</type></entry>
6348       <entry></entry>
6349       <entry>Role automatically inherits privileges of roles it is a
6350        member of</entry>
6351      </row>
6352
6353      <row>
6354       <entry><structfield>rolcreaterole</structfield></entry>
6355       <entry><type>bool</type></entry>
6356       <entry></entry>
6357       <entry>Role can create more roles</entry>
6358      </row>
6359
6360      <row>
6361       <entry><structfield>rolcreatedb</structfield></entry>
6362       <entry><type>bool</type></entry>
6363       <entry></entry>
6364       <entry>Role can create databases</entry>
6365      </row>
6366
6367      <row>
6368       <entry><structfield>rolcatupdate</structfield></entry>
6369       <entry><type>bool</type></entry>
6370       <entry></entry>
6371       <entry>
6372        Role can update system catalogs directly.  (Even a superuser cannot do
6373        this unless this column is true.)
6374       </entry>
6375      </row>
6376
6377      <row>
6378       <entry><structfield>rolcanlogin</structfield></entry>
6379       <entry><type>bool</type></entry>
6380       <entry></entry>
6381       <entry>
6382        Role can log in. That is, this role can be given as the initial
6383        session authorization identifier
6384       </entry>
6385      </row>
6386
6387      <row>
6388       <entry><structfield>rolconnlimit</structfield></entry>
6389       <entry><type>int4</type></entry>
6390       <entry></entry>
6391       <entry>
6392        For roles that can log in, this sets maximum number of concurrent
6393        connections this role can make.  -1 means no limit
6394       </entry>
6395      </row>
6396
6397      <row>
6398       <entry><structfield>rolpassword</structfield></entry>
6399       <entry><type>text</type></entry>
6400       <entry></entry>
6401       <entry>Not the password (always reads as <literal>********</>)</entry>
6402      </row>
6403
6404      <row>
6405       <entry><structfield>rolvaliduntil</structfield></entry>
6406       <entry><type>timestamptz</type></entry>
6407       <entry></entry>
6408       <entry>Password expiry time (only used for password authentication);
6409        NULL if no expiration</entry>
6410      </row>
6411
6412      <row>
6413       <entry><structfield>rolconfig</structfield></entry>
6414       <entry><type>text[]</type></entry>
6415       <entry></entry>
6416       <entry>Session defaults for run-time configuration variables</entry>
6417      </row>
6418
6419      <row>
6420       <entry><structfield>oid</structfield></entry>
6421       <entry><type>oid</type></entry>
6422       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
6423       <entry>ID of role</entry>
6424      </row>
6425     </tbody>
6426    </tgroup>
6427   </table>
6428
6429  </sect1>
6430
6431  <sect1 id="view-pg-rules">
6432   <title><structname>pg_rules</structname></title>
6433
6434   <indexterm zone="view-pg-rules">
6435    <primary>pg_rules</primary>
6436   </indexterm>
6437
6438   <para>
6439    The view <structname>pg_rules</structname> provides access to
6440    useful information about query rewrite rules.
6441   </para>
6442
6443   <table>
6444    <title><structname>pg_rules</> Columns</title>
6445
6446    <tgroup cols="4">
6447     <thead>
6448      <row>
6449       <entry>Name</entry>
6450       <entry>Type</entry>
6451       <entry>References</entry>
6452       <entry>Description</entry>
6453      </row>
6454     </thead>
6455     <tbody>
6456      <row>
6457       <entry><structfield>schemaname</structfield></entry>
6458       <entry><type>name</type></entry>
6459       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.nspname</literal></entry>
6460       <entry>Name of schema containing table</entry>
6461      </row>
6462      <row>
6463       <entry><structfield>tablename</structfield></entry>
6464       <entry><type>name</type></entry>
6465       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.relname</literal></entry>
6466       <entry>Name of table the rule is for</entry>
6467      </row>
6468      <row>
6469       <entry><structfield>rulename</structfield></entry>
6470       <entry><type>name</type></entry>
6471       <entry><literal><link linkend="catalog-pg-rewrite"><structname>pg_rewrite</structname></link>.rulename</literal></entry>
6472       <entry>Name of rule</entry>
6473      </row>
6474      <row>
6475       <entry><structfield>definition</structfield></entry>
6476       <entry><type>text</type></entry>
6477       <entry></entry>
6478       <entry>Rule definition (a reconstructed creation command)</entry>
6479      </row>
6480     </tbody>
6481    </tgroup>
6482   </table>
6483
6484   <para>
6485    The <structname>pg_rules</> view excludes the <literal>ON SELECT</> rules
6486    of views; those can be seen in <structname>pg_views</>.
6487   </para>
6488
6489  </sect1>
6490
6491  <sect1 id="view-pg-settings">
6492   <title><structname>pg_settings</structname></title>
6493
6494   <indexterm zone="view-pg-settings">
6495    <primary>pg_settings</primary>
6496   </indexterm>
6497
6498   <para>
6499    The view <structname>pg_settings</structname> provides access to
6500    run-time parameters of the server.  It is essentially an alternative
6501    interface to the <xref linkend="sql-show" endterm="sql-show-title">
6502    and <xref linkend="sql-set" endterm="sql-set-title"> commands.
6503    It also provides access to some facts about each parameter that are
6504    not directly available from <command>SHOW</>, such as minimum and
6505    maximum values.
6506   </para>
6507
6508   <table>
6509    <title><structname>pg_settings</> Columns</title>
6510
6511    <tgroup cols="3">
6512     <thead>
6513      <row>
6514       <entry>Name</entry>
6515       <entry>Type</entry>
6516       <entry>Description</entry>
6517      </row>
6518     </thead>
6519     <tbody>
6520      <row>
6521       <entry><structfield>name</structfield></entry>
6522       <entry><type>text</type></entry>
6523       <entry>Run-time configuration parameter name</entry>
6524      </row>
6525      <row>
6526       <entry><structfield>setting</structfield></entry>
6527       <entry><type>text</type></entry>
6528       <entry>Current value of the parameter</entry>
6529      </row>
6530      <row>
6531       <entry><structfield>unit</structfield></entry>
6532       <entry><type>text</type></entry>
6533       <entry>Implicit unit of the parameter</entry>
6534      </row>
6535      <row>
6536       <entry><structfield>category</structfield></entry>
6537       <entry><type>text</type></entry>
6538       <entry>Logical group of the parameter</entry>
6539      </row>
6540      <row>
6541       <entry><structfield>short_desc</structfield></entry>
6542       <entry><type>text</type></entry>
6543       <entry>A brief description of the parameter</entry>
6544      </row>
6545      <row>
6546       <entry><structfield>extra_desc</structfield></entry>
6547       <entry><type>text</type></entry>
6548       <entry>Additional, more detailed, description of the parameter</entry>
6549      </row>
6550      <row>
6551       <entry><structfield>context</structfield></entry>
6552       <entry><type>text</type></entry>
6553       <entry>Context required to set the parameter's value</entry>
6554      </row>
6555      <row>
6556       <entry><structfield>vartype</structfield></entry>
6557       <entry><type>text</type></entry>
6558       <entry>Parameter type (<literal>bool</>, <literal>enum</>,
6559        <literal>integer</>, <literal>real</>, or <literal>string</>)
6560       </entry>
6561      </row>
6562      <row>
6563       <entry><structfield>source</structfield></entry>
6564       <entry><type>text</type></entry>
6565       <entry>Source of the current parameter value</entry>
6566      </row>
6567      <row>
6568       <entry><structfield>min_val</structfield></entry>
6569       <entry><type>text</type></entry>
6570       <entry>Minimum allowed value of the parameter (NULL for non-numeric
6571       values)</entry>
6572      </row>
6573      <row>
6574       <entry><structfield>max_val</structfield></entry>
6575       <entry><type>text</type></entry>
6576       <entry>Maximum allowed value of the parameter (NULL for non-numeric
6577       values)</entry>
6578      </row>
6579      <row>
6580       <entry><structfield>enumvals</structfield></entry>
6581       <entry><type>text[]</type></entry>
6582       <entry>Allowed values of an enum parameter (NULL for non-enum
6583       values)</entry>
6584      </row>
6585      <row>
6586       <entry><structfield>boot_val</structfield></entry>
6587       <entry><type>text</type></entry>
6588       <entry>Parameter value assumed at server startup if the parameter is
6589       not otherwise set</entry>
6590      </row>
6591      <row>
6592       <entry><structfield>reset_val</structfield></entry>
6593       <entry><type>text</type></entry>
6594       <entry>Value that <command>RESET</command> would reset the parameter to
6595       in the current session</entry>
6596      </row>
6597      <row>
6598       <entry><structfield>sourcefile</structfield></entry>
6599       <entry><type>text</type></entry>
6600       <entry>Configuration file the current value was set in (NULL for
6601       values set from sources other than configuration files, or when
6602       examined by a non-superuser).
6603       Helpful when using configuration include directives</entry>
6604      </row>
6605      <row>
6606       <entry><structfield>sourceline</structfield></entry>
6607       <entry><type>integer</type></entry>
6608       <entry>Line number within the configuration file the current value was
6609       set at (NULL for values set from sources other than configuration files,
6610       or when examined by a non-superuser)
6611       </entry>
6612      </row>
6613     </tbody>
6614    </tgroup>
6615   </table>
6616
6617   <para>
6618    The <structname>pg_settings</structname> view cannot be inserted into or
6619    deleted from, but it can be updated.  An <command>UPDATE</command> applied
6620    to a row of <structname>pg_settings</structname> is equivalent to executing
6621    the <xref linkend="sql-set" endterm="sql-set-title"> command on that named
6622    parameter. The change only affects the value used by the current
6623    session. If an <command>UPDATE</command> is issued within a transaction
6624    that is later aborted, the effects of the <command>UPDATE</command> command
6625    disappear when the transaction is rolled back. Once the surrounding
6626    transaction is committed, the effects will persist until the end of the
6627    session, unless overridden by another <command>UPDATE</command> or
6628    <command>SET</command>.
6629   </para>
6630
6631  </sect1>
6632
6633  <sect1 id="view-pg-shadow">
6634   <title><structname>pg_shadow</structname></title>
6635
6636   <indexterm zone="view-pg-shadow">
6637    <primary>pg_shadow</primary>
6638   </indexterm>
6639
6640   <para>
6641    The view <structname>pg_shadow</structname> exists for backwards
6642    compatibility: it emulates a catalog that existed in
6643    <productname>PostgreSQL</productname> before version 8.1.
6644    It shows properties of all roles that are marked as
6645    <structfield>rolcanlogin</>.
6646   </para>
6647
6648   <para>
6649    The name stems from the fact that this table
6650    should not be readable by the public since it contains passwords.
6651    <link linkend="view-pg-user"><structname>pg_user</structname></link>
6652    is a publicly readable view on
6653    <structname>pg_shadow</structname> that blanks out the password field.
6654   </para>
6655
6656   <table>
6657    <title><structname>pg_shadow</> Columns</title>
6658
6659    <tgroup cols="4">
6660     <thead>
6661      <row>
6662       <entry>Name</entry>
6663       <entry>Type</entry>
6664       <entry>References</entry>
6665       <entry>Description</entry>
6666      </row>
6667     </thead>
6668
6669     <tbody>
6670      <row>
6671       <entry><structfield>usename</structfield></entry>
6672       <entry><type>name</type></entry>
6673       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.rolname</literal></entry>
6674       <entry>User name</entry>
6675      </row>
6676
6677      <row>
6678       <entry><structfield>usesysid</structfield></entry>
6679       <entry><type>oid</type></entry>
6680       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
6681       <entry>ID of this user</entry>
6682      </row>
6683
6684      <row>
6685       <entry><structfield>usecreatedb</structfield></entry>
6686       <entry><type>bool</type></entry>
6687       <entry></entry>
6688       <entry>User can create databases</entry>
6689      </row>
6690
6691      <row>
6692       <entry><structfield>usesuper</structfield></entry>
6693       <entry><type>bool</type></entry>
6694       <entry></entry>
6695       <entry>User is a superuser</entry>
6696      </row>
6697
6698      <row>
6699       <entry><structfield>usecatupd</structfield></entry>
6700       <entry><type>bool</type></entry>
6701       <entry></entry>
6702       <entry>
6703        User can update system catalogs.  (Even a superuser cannot do
6704        this unless this column is true.)
6705       </entry>
6706      </row>
6707
6708      <row>
6709       <entry><structfield>passwd</structfield></entry>
6710       <entry><type>text</type></entry>
6711       <entry></entry>
6712       <entry>Password (possibly encrypted)</entry>
6713      </row>
6714
6715      <row>
6716       <entry><structfield>valuntil</structfield></entry>
6717       <entry><type>abstime</type></entry>
6718       <entry></entry>
6719       <entry>Password expiry time (only used for password authentication)</entry>
6720      </row>
6721
6722      <row>
6723       <entry><structfield>useconfig</structfield></entry>
6724       <entry><type>text[]</type></entry>
6725       <entry></entry>
6726       <entry>Session defaults for run-time configuration variables</entry>
6727      </row>
6728     </tbody>
6729    </tgroup>
6730   </table>
6731
6732  </sect1>
6733
6734  <sect1 id="view-pg-stats">
6735   <title><structname>pg_stats</structname></title>
6736
6737   <indexterm zone="view-pg-stats">
6738    <primary>pg_stats</primary>
6739   </indexterm>
6740
6741   <para>
6742    The view <structname>pg_stats</structname> provides access to
6743    the information stored in the <link
6744    linkend="catalog-pg-statistic"><structname>pg_statistic</structname></link>
6745    catalog.  This view allows access only to rows of
6746    <structname>pg_statistic</structname> that correspond to tables the
6747    user has permission to read, and therefore it is safe to allow public
6748    read access to this view.
6749   </para>
6750
6751   <para>
6752    <structname>pg_stats</structname> is also designed to present the
6753    information in a more readable format than the underlying catalog
6754    &mdash; at the cost that its schema must be extended whenever new slot types
6755    are defined for <structname>pg_statistic</structname>.
6756   </para>
6757
6758   <table>
6759    <title><structname>pg_stats</> Columns</title>
6760
6761    <tgroup cols="4">
6762     <thead>
6763      <row>
6764       <entry>Name</entry>
6765       <entry>Type</entry>
6766       <entry>References</entry>
6767       <entry>Description</entry>
6768      </row>
6769     </thead>
6770     <tbody>
6771      <row>
6772       <entry><structfield>schemaname</structfield></entry>
6773       <entry><type>name</type></entry>
6774       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.nspname</literal></entry>
6775       <entry>Name of schema containing table</entry>
6776      </row>
6777
6778      <row>
6779       <entry><structfield>tablename</structfield></entry>
6780       <entry><type>name</type></entry>
6781       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.relname</literal></entry>
6782       <entry>Name of table</entry>
6783      </row>
6784
6785      <row>
6786       <entry><structfield>attname</structfield></entry>
6787       <entry><type>name</type></entry>
6788       <entry><literal><link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.attname</literal></entry>
6789       <entry>Name of the column described by this row</entry>
6790      </row>
6791
6792      <row>
6793       <entry><structfield>null_frac</structfield></entry>
6794       <entry><type>real</type></entry>
6795       <entry></entry>
6796       <entry>Fraction of column entries that are null</entry>
6797      </row>
6798
6799      <row>
6800       <entry><structfield>avg_width</structfield></entry>
6801       <entry><type>integer</type></entry>
6802       <entry></entry>
6803       <entry>Average width in bytes of column's entries</entry>
6804      </row>
6805
6806      <row>
6807       <entry><structfield>n_distinct</structfield></entry>
6808       <entry><type>real</type></entry>
6809       <entry></entry>
6810       <entry>
6811        If greater than zero, the estimated number of distinct values in the
6812        column.  If less than zero, the negative of the number of distinct
6813        values divided by the number of rows.  (The negated form is used when
6814        <command>ANALYZE</> believes that the number of distinct values is
6815        likely to increase as the table grows; the positive form is used when
6816        the column seems to have a fixed number of possible values.)  For
6817        example, -1 indicates a unique column in which the number of distinct
6818        values is the same as the number of rows
6819       </entry>
6820      </row>
6821
6822      <row>
6823       <entry><structfield>most_common_vals</structfield></entry>
6824       <entry><type>anyarray</type></entry>
6825       <entry></entry>
6826       <entry>
6827        A list of the most common values in the column. (NULL if
6828        no values seem to be more common than any others.)
6829        For some datatypes such as <type>tsvector</>, this is a list of
6830        the most common element values rather than values of the type itself.
6831       </entry>
6832      </row>
6833
6834      <row>
6835       <entry><structfield>most_common_freqs</structfield></entry>
6836       <entry><type>real[]</type></entry>
6837       <entry></entry>
6838       <entry>
6839        A list of the frequencies of the most common values or elements,
6840        i.e., number of occurrences of each divided by total number of rows.
6841        (NULL when <structfield>most_common_vals</structfield> is.)
6842        For some datatypes such as <type>tsvector</>, it can also store some
6843        additional information, making it longer than the
6844        <structfield>most_common_vals</> array.
6845       </entry>
6846      </row>
6847
6848      <row>
6849       <entry><structfield>histogram_bounds</structfield></entry>
6850       <entry><type>anyarray</type></entry>
6851       <entry></entry>
6852       <entry>
6853        A list of values that divide the column's values into groups of
6854        approximately equal population.  The values in
6855        <structfield>most_common_vals</>, if present, are omitted from this
6856        histogram calculation.  (This column is NULL if the column data type
6857        does not have a <literal>&lt;</> operator or if the
6858        <structfield>most_common_vals</> list accounts for the entire
6859        population.)
6860       </entry>
6861      </row>
6862
6863      <row>
6864       <entry><structfield>correlation</structfield></entry>
6865       <entry><type>real</type></entry>
6866       <entry></entry>
6867       <entry>
6868        Statistical correlation between physical row ordering and
6869        logical ordering of the column values.  This ranges from -1 to +1.
6870        When the value is near -1 or +1, an index scan on the column will
6871        be estimated to be cheaper than when it is near zero, due to reduction
6872        of random access to the disk.  (This column is NULL if the column data
6873        type does not have a <literal>&lt;</> operator.)
6874       </entry>
6875      </row>
6876     </tbody>
6877    </tgroup>
6878   </table>
6879
6880   <para>
6881    The maximum number of entries in the <structfield>most_common_vals</>
6882    and <structfield>histogram_bounds</> arrays can be set on a
6883    column-by-column basis using the <command>ALTER TABLE SET STATISTICS</>
6884    command, or globally by setting the
6885    <xref linkend="guc-default-statistics-target"> run-time parameter.
6886   </para>
6887
6888  </sect1>
6889
6890  <sect1 id="view-pg-tables">
6891   <title><structname>pg_tables</structname></title>
6892
6893   <indexterm zone="view-pg-tables">
6894    <primary>pg_tables</primary>
6895   </indexterm>
6896
6897   <para>
6898    The view <structname>pg_tables</structname> provides access to
6899    useful information about each table in the database.
6900   </para>
6901
6902   <table>
6903    <title><structname>pg_tables</> Columns</title>
6904
6905    <tgroup cols="4">
6906     <thead>
6907      <row>
6908       <entry>Name</entry>
6909       <entry>Type</entry>
6910       <entry>References</entry>
6911       <entry>Description</entry>
6912      </row>
6913     </thead>
6914     <tbody>
6915      <row>
6916       <entry><structfield>schemaname</structfield></entry>
6917       <entry><type>name</type></entry>
6918       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.nspname</literal></entry>
6919       <entry>Name of schema containing table</entry>
6920      </row>
6921      <row>
6922       <entry><structfield>tablename</structfield></entry>
6923       <entry><type>name</type></entry>
6924       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.relname</literal></entry>
6925       <entry>Name of table</entry>
6926      </row>
6927      <row>
6928       <entry><structfield>tableowner</structfield></entry>
6929       <entry><type>name</type></entry>
6930       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.rolname</literal></entry>
6931       <entry>Name of table's owner</entry>
6932      </row>
6933      <row>
6934       <entry><structfield>tablespace</structfield></entry>
6935       <entry><type>name</type></entry>
6936       <entry><literal><link linkend="catalog-pg-tablespace"><structname>pg_tablespace</structname></link>.spcname</literal></entry>
6937       <entry>Name of tablespace containing table (NULL if default for database)</entry>
6938      </row>
6939      <row>
6940       <entry><structfield>hasindexes</structfield></entry>
6941       <entry><type>boolean</type></entry>
6942       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.relhasindex</literal></entry>
6943       <entry>true if table has (or recently had) any indexes</entry>
6944      </row>
6945      <row>
6946       <entry><structfield>hasrules</structfield></entry>
6947       <entry><type>boolean</type></entry>
6948       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.relhasrules</literal></entry>
6949       <entry>true if table has (or once had) rules</entry>
6950      </row>
6951      <row>
6952       <entry><structfield>hastriggers</structfield></entry>
6953       <entry><type>boolean</type></entry>
6954       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.relhastriggers</literal></entry>
6955       <entry>true if table has (or once had) triggers</entry>
6956      </row>
6957     </tbody>
6958    </tgroup>
6959   </table>
6960
6961  </sect1>
6962
6963  <sect1 id="view-pg-timezone-abbrevs">
6964   <title><structname>pg_timezone_abbrevs</structname></title>
6965
6966   <indexterm zone="view-pg-timezone-abbrevs">
6967    <primary>pg_timezone_abbrevs</primary>
6968   </indexterm>
6969
6970   <para>
6971    The view <structname>pg_timezone_abbrevs</structname> provides a list
6972    of time zone abbreviations that are currently recognized by the datetime
6973    input routines.  The contents of this view change when the
6974    <xref linkend="guc-timezone-abbreviations"> run-time parameter is modified.
6975   </para>
6976
6977   <table>
6978    <title><structname>pg_timezone_abbrevs</> Columns</title>
6979
6980    <tgroup cols="3">
6981     <thead>
6982      <row>
6983       <entry>Name</entry>
6984       <entry>Type</entry>
6985       <entry>Description</entry>
6986      </row>
6987     </thead>
6988     <tbody>
6989      <row>
6990       <entry><structfield>abbrev</structfield></entry>
6991       <entry><type>text</type></entry>
6992       <entry>Time zone abbreviation</entry>
6993      </row>
6994      <row>
6995       <entry><structfield>utc_offset</structfield></entry>
6996       <entry><type>interval</type></entry>
6997       <entry>Offset from UTC (positive means east of Greenwich)</entry>
6998      </row>
6999      <row>
7000       <entry><structfield>is_dst</structfield></entry>
7001       <entry><type>boolean</type></entry>
7002       <entry>True if this is a daylight-savings abbreviation</entry>
7003      </row>
7004     </tbody>
7005    </tgroup>
7006   </table>
7007
7008  </sect1>
7009
7010  <sect1 id="view-pg-timezone-names">
7011   <title><structname>pg_timezone_names</structname></title>
7012
7013   <indexterm zone="view-pg-timezone-names">
7014    <primary>pg_timezone_names</primary>
7015   </indexterm>
7016
7017   <para>
7018    The view <structname>pg_timezone_names</structname> provides a list
7019    of time zone names that are recognized by <command>SET TIMEZONE</>,
7020    along with their associated abbreviations, UTC offsets,
7021    and daylight-savings status.
7022    Unlike the abbreviations shown in <link
7023    linkend="view-pg-timezone-abbrevs"><structname>pg_timezone_abbrevs</structname></link>, many of these names imply a set of daylight-savings transition
7024    date rules.  Therefore, the associated information changes across local DST
7025    boundaries.  The displayed information is computed based on the current
7026    value of <function>CURRENT_TIMESTAMP</>.
7027   </para>
7028
7029   <table>
7030    <title><structname>pg_timezone_names</> Columns</title>
7031
7032    <tgroup cols="3">
7033     <thead>
7034      <row>
7035       <entry>Name</entry>
7036       <entry>Type</entry>
7037       <entry>Description</entry>
7038      </row>
7039     </thead>
7040     <tbody>
7041      <row>
7042       <entry><structfield>name</structfield></entry>
7043       <entry><type>text</type></entry>
7044       <entry>Time zone name</entry>
7045      </row>
7046      <row>
7047       <entry><structfield>abbrev</structfield></entry>
7048       <entry><type>text</type></entry>
7049       <entry>Time zone abbreviation</entry>
7050      </row>
7051      <row>
7052       <entry><structfield>utc_offset</structfield></entry>
7053       <entry><type>interval</type></entry>
7054       <entry>Offset from UTC (positive means east of Greenwich)</entry>
7055      </row>
7056      <row>
7057       <entry><structfield>is_dst</structfield></entry>
7058       <entry><type>boolean</type></entry>
7059       <entry>True if currently observing daylight savings</entry>
7060      </row>
7061     </tbody>
7062    </tgroup>
7063   </table>
7064
7065  </sect1>
7066
7067  <sect1 id="view-pg-user">
7068   <title><structname>pg_user</structname></title>
7069
7070   <indexterm zone="view-pg-user">
7071    <primary>pg_user</primary>
7072   </indexterm>
7073
7074   <para>
7075    The view <structname>pg_user</structname> provides access to
7076    information about database users.  This is simply a publicly
7077    readable view of
7078    <link linkend="view-pg-shadow"><structname>pg_shadow</structname></link>
7079    that blanks out the password field.
7080   </para>
7081
7082   <table>
7083    <title><structname>pg_user</> Columns</title>
7084
7085    <tgroup cols="3">
7086     <thead>
7087      <row>
7088       <entry>Name</entry>
7089       <entry>Type</entry>
7090       <entry>Description</entry>
7091      </row>
7092     </thead>
7093     <tbody>
7094      <row>
7095       <entry><structfield>usename</structfield></entry>
7096       <entry><type>name</type></entry>
7097       <entry>User name</entry>
7098      </row>
7099
7100      <row>
7101       <entry><structfield>usesysid</structfield></entry>
7102       <entry><type>int4</type></entry>
7103       <entry>User ID (arbitrary number used to reference this user)</entry>
7104      </row>
7105
7106      <row>
7107       <entry><structfield>usecreatedb</structfield></entry>
7108       <entry><type>bool</type></entry>
7109       <entry>User can create databases</entry>
7110      </row>
7111
7112      <row>
7113       <entry><structfield>usesuper</structfield></entry>
7114       <entry><type>bool</type></entry>
7115       <entry>User is a superuser</entry>
7116      </row>
7117
7118      <row>
7119       <entry><structfield>usecatupd</structfield></entry>
7120       <entry><type>bool</type></entry>
7121       <entry>
7122        User can update system catalogs.  (Even a superuser cannot do
7123        this unless this column is true.)
7124       </entry>
7125      </row>
7126
7127      <row>
7128       <entry><structfield>passwd</structfield></entry>
7129       <entry><type>text</type></entry>
7130       <entry>Not the password (always reads as <literal>********</>)</entry>
7131      </row>
7132
7133      <row>
7134       <entry><structfield>valuntil</structfield></entry>
7135       <entry><type>abstime</type></entry>
7136       <entry>Password expiry time (only used for password authentication)</entry>
7137      </row>
7138
7139      <row>
7140       <entry><structfield>useconfig</structfield></entry>
7141       <entry><type>text[]</type></entry>
7142       <entry>Session defaults for run-time configuration variables</entry>
7143      </row>
7144     </tbody>
7145    </tgroup>
7146   </table>
7147
7148  </sect1>
7149
7150  <sect1 id="view-pg-user-mappings">
7151   <title><structname>pg_user_mappings</structname></title>
7152
7153   <indexterm zone="view-pg-user-mappings">
7154    <primary>pg_user_mappings</primary>
7155   </indexterm>
7156
7157   <para>
7158    The view <structname>pg_user_mappings</structname> provides access
7159    to information about user mappings.  This is essentially a publicly
7160    readable view of
7161    <link linkend="catalog-pg-user-mapping"><structname>pg_user_mapping</structname></link>
7162    that leaves out the options field if the user has no rights to use
7163    it.
7164   </para>
7165
7166   <table>
7167    <title><structname>pg_user_mappings</> Columns</title>
7168
7169    <tgroup cols="3">
7170     <thead>
7171      <row>
7172       <entry>Name</entry>
7173       <entry>Type</entry>
7174       <entry>References</entry>
7175       <entry>Description</entry>
7176      </row>
7177     </thead>
7178
7179     <tbody>
7180      <row>
7181       <entry><structfield>umid</structfield></entry>
7182       <entry><type>oid</type></entry>
7183       <entry><literal><link linkend="catalog-pg-user-mapping"><structname>pg_user_mapping</structname></link>.oid</literal></entry>
7184       <entry>OID of the user mapping</entry>
7185      </row>
7186
7187      <row>
7188       <entry><structfield>srvid</structfield></entry>
7189       <entry><type>oid</type></entry>
7190       <entry><literal><link linkend="catalog-pg-foreign-server"><structname>pg_foreign_server</structname></link>.oid</literal></entry>
7191       <entry>
7192        The OID of the foreign server that contains this mapping
7193       </entry>
7194      </row>
7195
7196      <row>
7197       <entry><structfield>srvname</structfield></entry>
7198       <entry><type>text</type></entry>
7199       <entry></entry>
7200       <entry>
7201        Name of the foreign server
7202       </entry>
7203      </row>
7204
7205      <row>
7206       <entry><structfield>umuser</structfield></entry>
7207       <entry><type>oid</type></entry>
7208       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
7209       <entry>OID of the local role being mapped, 0 if the user mapping is public</entry>
7210      </row>
7211
7212      <row>
7213       <entry><structfield>usename</structfield></entry>
7214       <entry><type>name</type></entry>
7215       <entry></entry>
7216       <entry>Name of the local user to be mapped</entry>
7217      </row>
7218
7219      <row>
7220       <entry><structfield>umoptions</structfield></entry>
7221       <entry><type>text[]</type></entry>
7222       <entry></entry>
7223       <entry>
7224        User mapping specific options, as <quote>keyword=value</>
7225        strings, if the current user is the owner of the foreign
7226        server, else null.
7227       </entry>
7228      </row>
7229     </tbody>
7230    </tgroup>
7231   </table>
7232  </sect1>
7233
7234
7235  <sect1 id="view-pg-views">
7236   <title><structname>pg_views</structname></title>
7237
7238   <indexterm zone="view-pg-views">
7239    <primary>pg_views</primary>
7240   </indexterm>
7241
7242   <para>
7243    The view <structname>pg_views</structname> provides access to
7244    useful information about each view in the database.
7245   </para>
7246
7247   <table>
7248    <title><structname>pg_views</> Columns</title>
7249
7250    <tgroup cols="4">
7251     <thead>
7252      <row>
7253       <entry>Name</entry>
7254       <entry>Type</entry>
7255       <entry>References</entry>
7256       <entry>Description</entry>
7257      </row>
7258     </thead>
7259     <tbody>
7260      <row>
7261       <entry><structfield>schemaname</structfield></entry>
7262       <entry><type>name</type></entry>
7263       <entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.nspname</literal></entry>
7264       <entry>Name of schema containing view</entry>
7265      </row>
7266      <row>
7267       <entry><structfield>viewname</structfield></entry>
7268       <entry><type>name</type></entry>
7269       <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.relname</literal></entry>
7270       <entry>Name of view</entry>
7271      </row>
7272      <row>
7273       <entry><structfield>viewowner</structfield></entry>
7274       <entry><type>name</type></entry>
7275       <entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.rolname</literal></entry>
7276       <entry>Name of view's owner</entry>
7277      </row>
7278      <row>
7279       <entry><structfield>definition</structfield></entry>
7280       <entry><type>text</type></entry>
7281       <entry></entry>
7282       <entry>View definition (a reconstructed <command>SELECT</command> query)</entry>
7283      </row>
7284     </tbody>
7285    </tgroup>
7286   </table>
7287
7288  </sect1>
7289
7290 </chapter>