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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>52.2. pg_aggregate</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="catalogs-overview.html" title="52.1. Overview" /><link rel="next" href="catalog-pg-am.html" title="52.3. pg_am" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">52.2. <code class="structname">pg_aggregate</code></th></tr><tr><td width="10%" align="left"><a accesskey="p" href="catalogs-overview.html" title="52.1. Overview">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-am.html" title="52.3. pg_am">Next</a></td></tr></table><hr /></div><div class="sect1" id="CATALOG-PG-AGGREGATE"><div class="titlepage"><div><div><h2 class="title" style="clear: both">52.2. <code class="structname">pg_aggregate</code> <a href="#CATALOG-PG-AGGREGATE" class="id_link">#</a></h2></div></div></div><a id="id-1.10.4.4.2" class="indexterm"></a><p>
   3    The catalog <code class="structname">pg_aggregate</code> stores information about
   4    aggregate functions.  An aggregate function is a function that
   5    operates on a set of values (typically one column from each row
   6    that matches a query condition) and returns a single value computed
   7    from all these values.  Typical aggregate functions are
   8    <code class="function">sum</code>, <code class="function">count</code>, and
   9    <code class="function">max</code>.  Each entry in
  10    <code class="structname">pg_aggregate</code> is an extension of an entry
  11    in <a class="link" href="catalog-pg-proc.html" title="52.39. pg_proc"><code class="structname">pg_proc</code></a>.
  12    The <code class="structname">pg_proc</code> entry carries the aggregate's name,
  13    input and output data types, and other information that is similar to
  14    ordinary functions.
  15   </p><div class="table" id="id-1.10.4.4.4"><p class="title"><strong>Table 52.2. <code class="structname">pg_aggregate</code> Columns</strong></p><div class="table-contents"><table class="table" summary="pg_aggregate Columns" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
  16        Column Type
  17       </p>
  18       <p>
  19        Description
  20       </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
  21        <code class="structfield">aggfnoid</code> <code class="type">regproc</code>
  22        (references <a class="link" href="catalog-pg-proc.html" title="52.39. pg_proc"><code class="structname">pg_proc</code></a>.<code class="structfield">oid</code>)
  23       </p>
  24       <p>
  25        <code class="structname">pg_proc</code> OID of the aggregate function
  26       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  27        <code class="structfield">aggkind</code> <code class="type">char</code>
  28       </p>
  29       <p>
  30        Aggregate kind:
  31        <code class="literal">n</code> for <span class="quote">“<span class="quote">normal</span>”</span> aggregates,
  32        <code class="literal">o</code> for <span class="quote">“<span class="quote">ordered-set</span>”</span> aggregates, or
  33        <code class="literal">h</code> for <span class="quote">“<span class="quote">hypothetical-set</span>”</span> aggregates
  34       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  35        <code class="structfield">aggnumdirectargs</code> <code class="type">int2</code>
  36       </p>
  37       <p>
  38        Number of direct (non-aggregated) arguments of an ordered-set or
  39        hypothetical-set aggregate, counting a variadic array as one argument.
  40        If equal to <code class="structfield">pronargs</code>, the aggregate must be variadic
  41        and the variadic array describes the aggregated arguments as well as
  42        the final direct arguments.
  43        Always zero for normal aggregates.
  44       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  45        <code class="structfield">aggtransfn</code> <code class="type">regproc</code>
  46        (references <a class="link" href="catalog-pg-proc.html" title="52.39. pg_proc"><code class="structname">pg_proc</code></a>.<code class="structfield">oid</code>)
  47       </p>
  48       <p>
  49        Transition function
  50       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  51        <code class="structfield">aggfinalfn</code> <code class="type">regproc</code>
  52        (references <a class="link" href="catalog-pg-proc.html" title="52.39. pg_proc"><code class="structname">pg_proc</code></a>.<code class="structfield">oid</code>)
  53       </p>
  54       <p>
  55        Final function (zero if none)
  56       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  57        <code class="structfield">aggcombinefn</code> <code class="type">regproc</code>
  58        (references <a class="link" href="catalog-pg-proc.html" title="52.39. pg_proc"><code class="structname">pg_proc</code></a>.<code class="structfield">oid</code>)
  59       </p>
  60       <p>
  61        Combine function (zero if none)
  62       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  63        <code class="structfield">aggserialfn</code> <code class="type">regproc</code>
  64        (references <a class="link" href="catalog-pg-proc.html" title="52.39. pg_proc"><code class="structname">pg_proc</code></a>.<code class="structfield">oid</code>)
  65       </p>
  66       <p>
  67        Serialization function (zero if none)
  68       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  69        <code class="structfield">aggdeserialfn</code> <code class="type">regproc</code>
  70        (references <a class="link" href="catalog-pg-proc.html" title="52.39. pg_proc"><code class="structname">pg_proc</code></a>.<code class="structfield">oid</code>)
  71       </p>
  72       <p>
  73        Deserialization function (zero if none)
  74       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  75        <code class="structfield">aggmtransfn</code> <code class="type">regproc</code>
  76        (references <a class="link" href="catalog-pg-proc.html" title="52.39. pg_proc"><code class="structname">pg_proc</code></a>.<code class="structfield">oid</code>)
  77       </p>
  78       <p>
  79        Forward transition function for moving-aggregate mode (zero if none)
  80       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  81        <code class="structfield">aggminvtransfn</code> <code class="type">regproc</code>
  82        (references <a class="link" href="catalog-pg-proc.html" title="52.39. pg_proc"><code class="structname">pg_proc</code></a>.<code class="structfield">oid</code>)
  83       </p>
  84       <p>
  85        Inverse transition function for moving-aggregate mode (zero if none)
  86       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  87        <code class="structfield">aggmfinalfn</code> <code class="type">regproc</code>
  88        (references <a class="link" href="catalog-pg-proc.html" title="52.39. pg_proc"><code class="structname">pg_proc</code></a>.<code class="structfield">oid</code>)
  89       </p>
  90       <p>
  91        Final function for moving-aggregate mode (zero if none)
  92       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  93        <code class="structfield">aggfinalextra</code> <code class="type">bool</code>
  94       </p>
  95       <p>
  96        True to pass extra dummy arguments to <code class="structfield">aggfinalfn</code>
  97       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  98        <code class="structfield">aggmfinalextra</code> <code class="type">bool</code>
  99       </p>
 100       <p>
 101        True to pass extra dummy arguments to <code class="structfield">aggmfinalfn</code>
 102       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 103        <code class="structfield">aggfinalmodify</code> <code class="type">char</code>
 104       </p>
 105       <p>
 106        Whether <code class="structfield">aggfinalfn</code> modifies the
 107        transition state value:
 108        <code class="literal">r</code> if it is read-only,
 109        <code class="literal">s</code> if the <code class="structfield">aggtransfn</code>
 110        cannot be applied after the <code class="structfield">aggfinalfn</code>, or
 111        <code class="literal">w</code> if it writes on the value
 112       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 113        <code class="structfield">aggmfinalmodify</code> <code class="type">char</code>
 114       </p>
 115       <p>
 116        Like <code class="structfield">aggfinalmodify</code>, but for
 117        the <code class="structfield">aggmfinalfn</code>
 118       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 119        <code class="structfield">aggsortop</code> <code class="type">oid</code>
 120        (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>)
 121       </p>
 122       <p>
 123        Associated sort operator (zero if none)
 124       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 125        <code class="structfield">aggtranstype</code> <code class="type">oid</code>
 126        (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>)
 127       </p>
 128       <p>
 129        Data type of the aggregate function's internal transition (state) data
 130       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 131        <code class="structfield">aggtransspace</code> <code class="type">int4</code>
 132       </p>
 133       <p>
 134        Approximate average size (in bytes) of the transition state
 135        data, or zero to use a default estimate
 136       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 137        <code class="structfield">aggmtranstype</code> <code class="type">oid</code>
 138        (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>)
 139       </p>
 140       <p>
 141        Data type of the aggregate function's internal transition (state)
 142        data for moving-aggregate mode (zero if none)
 143       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 144        <code class="structfield">aggmtransspace</code> <code class="type">int4</code>
 145       </p>
 146       <p>
 147        Approximate average size (in bytes) of the transition state data
 148        for moving-aggregate mode, or zero to use a default estimate
 149       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 150        <code class="structfield">agginitval</code> <code class="type">text</code>
 151       </p>
 152       <p>
 153        The initial value of the transition state.  This is a text
 154        field containing the initial value in its external string
 155        representation.  If this field is null, the transition state
 156        value starts out null.
 157       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 158        <code class="structfield">aggminitval</code> <code class="type">text</code>
 159       </p>
 160       <p>
 161        The initial value of the transition state for moving-aggregate mode.
 162        This is a text field containing the initial value in its external
 163        string representation.  If this field is null, the transition state
 164        value starts out null.
 165       </p></td></tr></tbody></table></div></div><br class="table-break" /><p>
 166    New aggregate functions are registered with the <a class="link" href="sql-createaggregate.html" title="CREATE AGGREGATE"><code class="command">CREATE AGGREGATE</code></a>
 167    command.  See <a class="xref" href="xaggr.html" title="36.12. User-Defined Aggregates">Section 36.12</a> for more information about
 168    writing aggregate functions and the meaning of the transition
 169    functions, etc.
 170   </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="catalogs-overview.html" title="52.1. Overview">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-am.html" title="52.3. pg_am">Next</a></td></tr><tr><td width="40%" align="left" valign="top">52.1. Overview </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"> 52.3. <code class="structname">pg_am</code></td></tr></table></div></body></html>