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   2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>52.20. pg_enum</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="catalog-pg-description.html" title="52.19. pg_description" /><link rel="next" href="catalog-pg-event-trigger.html" title="52.21. pg_event_trigger" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">52.20. <code class="structname">pg_enum</code></th></tr><tr><td width="10%" align="left"><a accesskey="p" href="catalog-pg-description.html" title="52.19. pg_description">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="catalogs.html" title="Chapter 52. System Catalogs">Up</a></td><th width="60%" align="center">Chapter 52. System Catalogs</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 18.0 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="catalog-pg-event-trigger.html" title="52.21. pg_event_trigger">Next</a></td></tr></table><hr /></div><div class="sect1" id="CATALOG-PG-ENUM"><div class="titlepage"><div><div><h2 class="title" style="clear: both">52.20. <code class="structname">pg_enum</code> <a href="#CATALOG-PG-ENUM" class="id_link">#</a></h2></div></div></div><a id="id-1.10.4.22.2" class="indexterm"></a><p>
   3    The <code class="structname">pg_enum</code> catalog contains entries
   4    showing the values and labels for each enum type. The
   5    internal representation of a given enum value is actually the OID
   6    of its associated row in <code class="structname">pg_enum</code>.
   7   </p><div class="table" id="id-1.10.4.22.4"><p class="title"><strong>Table 52.20. <code class="structname">pg_enum</code> Columns</strong></p><div class="table-contents"><table class="table" summary="pg_enum Columns" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
   8        Column Type
   9       </p>
  10       <p>
  11        Description
  12       </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
  13        <code class="structfield">oid</code> <code class="type">oid</code>
  14       </p>
  15       <p>
  16        Row identifier
  17       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  18        <code class="structfield">enumtypid</code> <code class="type">oid</code>
  19        (references <a class="link" href="catalog-pg-type.html" title="52.64. pg_type"><code class="structname">pg_type</code></a>.<code class="structfield">oid</code>)
  20       </p>
  21       <p>
  22        The OID of the <a class="link" href="catalog-pg-type.html" title="52.64. pg_type"><code class="structname">pg_type</code></a> entry owning this enum value
  23       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  24        <code class="structfield">enumsortorder</code> <code class="type">float4</code>
  25       </p>
  26       <p>
  27        The sort position of this enum value within its enum type
  28       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  29        <code class="structfield">enumlabel</code> <code class="type">name</code>
  30       </p>
  31       <p>
  32        The textual label for this enum value
  33       </p></td></tr></tbody></table></div></div><br class="table-break" /><p>
  34    The OIDs for <code class="structname">pg_enum</code> rows follow a special
  35    rule: even-numbered OIDs are guaranteed to be ordered in the same way
  36    as the sort ordering of their enum type.  That is, if two even OIDs
  37    belong to the same enum type, the smaller OID must have the smaller
  38    <code class="structfield">enumsortorder</code> value.  Odd-numbered OID values
  39    need bear no relationship to the sort order.  This rule allows the
  40    enum comparison routines to avoid catalog lookups in many common cases.
  41    The routines that create and alter enum types attempt to assign even
  42    OIDs to enum values whenever possible.
  43   </p><p>
  44    When an enum type is created, its members are assigned sort-order
  45    positions 1..<em class="replaceable"><code>n</code></em>.  But members added later might be given
  46    negative or fractional values of <code class="structfield">enumsortorder</code>.
  47    The only requirement on these values is that they be correctly
  48    ordered and unique within each enum type.
  49   </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="catalog-pg-description.html" title="52.19. pg_description">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="catalogs.html" title="Chapter 52. System Catalogs">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="catalog-pg-event-trigger.html" title="52.21. pg_event_trigger">Next</a></td></tr><tr><td width="40%" align="left" valign="top">52.19. <code class="structname">pg_description</code> </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 18.0 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 52.21. <code class="structname">pg_event_trigger</code></td></tr></table></div></body></html>