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