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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>52.4. pg_amop</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-am.html" title="52.3. pg_am" /><link rel="next" href="catalog-pg-amproc.html" title="52.5. pg_amproc" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">52.4. <code class="structname">pg_amop</code></th></tr><tr><td width="10%" align="left"><a accesskey="p" href="catalog-pg-am.html" title="52.3. pg_am">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-amproc.html" title="52.5. pg_amproc">Next</a></td></tr></table><hr /></div><div class="sect1" id="CATALOG-PG-AMOP"><div class="titlepage"><div><div><h2 class="title" style="clear: both">52.4. <code class="structname">pg_amop</code> <a href="#CATALOG-PG-AMOP" class="id_link">#</a></h2></div></div></div><a id="id-1.10.4.6.2" class="indexterm"></a><p>
   3    The catalog <code class="structname">pg_amop</code> stores information about
   4    operators associated with access method operator families.  There is one
   5    row for each operator that is a member of an operator family.  A family
   6    member can be either a <em class="firstterm">search</em> operator or an
   7    <em class="firstterm">ordering</em> operator.  An operator
   8    can appear in more than one family, but cannot appear in more than one
   9    search position nor more than one ordering position within a family.
  10    (It is allowed, though unlikely, for an operator to be used for both
  11    search and ordering purposes.)
  12   </p><div class="table" id="id-1.10.4.6.4"><p class="title"><strong>Table 52.4. <code class="structname">pg_amop</code> Columns</strong></p><div class="table-contents"><table class="table" summary="pg_amop Columns" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
  13        Column Type
  14       </p>
  15       <p>
  16        Description
  17       </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
  18        <code class="structfield">oid</code> <code class="type">oid</code>
  19       </p>
  20       <p>
  21        Row identifier
  22       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  23        <code class="structfield">amopfamily</code> <code class="type">oid</code>
  24        (references <a class="link" href="catalog-pg-opfamily.html" title="52.35. pg_opfamily"><code class="structname">pg_opfamily</code></a>.<code class="structfield">oid</code>)
  25       </p>
  26       <p>
  27        The operator family this entry is for
  28       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  29        <code class="structfield">amoplefttype</code> <code class="type">oid</code>
  30        (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>)
  31       </p>
  32       <p>
  33        Left-hand input data type of operator
  34       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  35        <code class="structfield">amoprighttype</code> <code class="type">oid</code>
  36        (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>)
  37       </p>
  38       <p>
  39        Right-hand input data type of operator
  40       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  41        <code class="structfield">amopstrategy</code> <code class="type">int2</code>
  42       </p>
  43       <p>
  44        Operator strategy number
  45       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  46        <code class="structfield">amoppurpose</code> <code class="type">char</code>
  47       </p>
  48       <p>
  49        Operator purpose, either <code class="literal">s</code> for search or
  50        <code class="literal">o</code> for ordering
  51       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  52        <code class="structfield">amopopr</code> <code class="type">oid</code>
  53        (references <a class="link" href="catalog-pg-operator.html" title="52.34. pg_operator"><code class="structname">pg_operator</code></a>.<code class="structfield">oid</code>)
  54       </p>
  55       <p>
  56        OID of the operator
  57       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  58        <code class="structfield">amopmethod</code> <code class="type">oid</code>
  59        (references <a class="link" href="catalog-pg-am.html" title="52.3. pg_am"><code class="structname">pg_am</code></a>.<code class="structfield">oid</code>)
  60       </p>
  61       <p>
  62        Index access method operator family is for
  63       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  64        <code class="structfield">amopsortfamily</code> <code class="type">oid</code>
  65        (references <a class="link" href="catalog-pg-opfamily.html" title="52.35. pg_opfamily"><code class="structname">pg_opfamily</code></a>.<code class="structfield">oid</code>)
  66       </p>
  67       <p>
  68        The B-tree operator family this entry sorts according to, if an
  69        ordering operator; zero if a search operator
  70       </p></td></tr></tbody></table></div></div><br class="table-break" /><p>
  71    A <span class="quote">“<span class="quote">search</span>”</span> operator entry indicates that an index of this operator
  72    family can be searched to find all rows satisfying
  73    <code class="literal">WHERE</code>
  74    <em class="replaceable"><code>indexed_column</code></em>
  75    <em class="replaceable"><code>operator</code></em>
  76    <em class="replaceable"><code>constant</code></em>.
  77    Obviously, such an operator must return <code class="type">boolean</code>, and its left-hand input
  78    type must match the index's column data type.
  79   </p><p>
  80    An <span class="quote">“<span class="quote">ordering</span>”</span> operator entry indicates that an index of this
  81    operator family can be scanned to return rows in the order represented by
  82    <code class="literal">ORDER BY</code>
  83    <em class="replaceable"><code>indexed_column</code></em>
  84    <em class="replaceable"><code>operator</code></em>
  85    <em class="replaceable"><code>constant</code></em>.
  86    Such an operator could return any sortable data type, though again
  87    its left-hand input type must match the index's column data type.
  88    The exact semantics of the <code class="literal">ORDER BY</code> are specified by the
  89    <code class="structfield">amopsortfamily</code> column, which must reference
  90    a B-tree operator family for the operator's result type.
  91   </p><div class="note"><h3 class="title">Note</h3><p>
  92     At present, it's assumed that the sort order for an ordering operator
  93     is the default for the referenced operator family, i.e., <code class="literal">ASC NULLS
  94     LAST</code>.  This might someday be relaxed by adding additional columns
  95     to specify sort options explicitly.
  96    </p></div><p>
  97    An entry's <code class="structfield">amopmethod</code> must match the
  98    <code class="structfield">opfmethod</code> of its containing operator family (including
  99    <code class="structfield">amopmethod</code> here is an intentional denormalization of the
 100    catalog structure for performance reasons).  Also,
 101    <code class="structfield">amoplefttype</code> and <code class="structfield">amoprighttype</code> must match
 102    the <code class="structfield">oprleft</code> and <code class="structfield">oprright</code> fields of the
 103    referenced <a class="link" href="catalog-pg-operator.html" title="52.34. pg_operator"><code class="structname">pg_operator</code></a> entry.
 104   </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="catalog-pg-am.html" title="52.3. pg_am">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-amproc.html" title="52.5. pg_amproc">Next</a></td></tr><tr><td width="40%" align="left" valign="top">52.3. <code class="structname">pg_am</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"> 52.5. <code class="structname">pg_amproc</code></td></tr></table></div></body></html>