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  1. <?xml version="1.0" encoding="UTF-8" standalone="no"?>

  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>CREATE LANGUAGE</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 V1.79.1" /><link rel="prev" href="sql-createindex.html" title="CREATE INDEX" /><link rel="next" href="sql-creatematerializedview.html" title="CREATE MATERIALIZED VIEW" /></head><body><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">CREATE LANGUAGE</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="sql-createindex.html" title="CREATE INDEX">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="sql-commands.html" title="SQL Commands">Up</a></td><th width="60%" align="center">SQL Commands</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 12.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="sql-creatematerializedview.html" title="CREATE MATERIALIZED VIEW">Next</a></td></tr></table><hr></hr></div><div class="refentry" id="SQL-CREATELANGUAGE"><div class="titlepage"></div><a id="id-1.9.3.70.1" class="indexterm"></a><div class="refnamediv"><h2><span class="refentrytitle">CREATE LANGUAGE</span></h2><p>CREATE LANGUAGE — define a new procedural language</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><pre class="synopsis">

  3. CREATE [ OR REPLACE ] [ PROCEDURAL ] LANGUAGE <em class="replaceable"><code>name</code></em>

  4. CREATE [ OR REPLACE ] [ TRUSTED ] [ PROCEDURAL ] LANGUAGE <em class="replaceable"><code>name</code></em>

  5.     HANDLER <em class="replaceable"><code>call_handler</code></em> [ INLINE <em class="replaceable"><code>inline_handler</code></em> ] [ VALIDATOR <em class="replaceable"><code>valfunction</code></em> ]

  6. </pre></div><div class="refsect1" id="SQL-CREATELANGUAGE-DESCRIPTION"><h2>Description</h2><p>

  7.    <code class="command">CREATE LANGUAGE</code> registers a new

  8.    procedural language with a <span class="productname">PostgreSQL</span>

  9.    database.  Subsequently, functions and procedures can be

  10.    defined in this new language.

  11.   </p><div class="note"><h3 class="title">Note</h3><p>

  12.     As of <span class="productname">PostgreSQL</span> 9.1, most procedural

  13.     languages have been made into <span class="quote">“<span class="quote">extensions</span>”</span>, and should

  14.     therefore be installed with <a class="xref" href="sql-createextension.html" title="CREATE EXTENSION"><span class="refentrytitle">CREATE EXTENSION</span></a>

  15.     not <code class="command">CREATE LANGUAGE</code>.  Direct use of

  16.     <code class="command">CREATE LANGUAGE</code> should now be confined to

  17.     extension installation scripts.  If you have a <span class="quote">“<span class="quote">bare</span>”</span>

  18.     language in your database, perhaps as a result of an upgrade,

  19.     you can convert it to an extension using

  20.     <code class="literal">CREATE EXTENSION <em class="replaceable"><code>langname</code></em> FROM

  21.     unpackaged</code>.

  22.    </p></div><p>

  23.    <code class="command">CREATE LANGUAGE</code> effectively associates the

  24.    language name with handler function(s) that are responsible for executing

  25.    functions written in the language.  Refer to <a class="xref" href="plhandler.html" title="Chapter 55. Writing a Procedural Language Handler">Chapter 55</a>

  26.    for more information about language handlers.

  27.   </p><p>

  28.    There are two forms of the <code class="command">CREATE LANGUAGE</code> command.

  29.    In the first form, the user supplies just the name of the desired

  30.    language, and the <span class="productname">PostgreSQL</span> server consults

  31.    the <a class="link" href="catalog-pg-pltemplate.html" title="51.37. pg_pltemplate"><code class="structname">pg_pltemplate</code></a>

  32.    system catalog to determine the correct parameters.  In the second form,

  33.    the user supplies the language parameters along with the language name.

  34.    The second form can be used to create a language that is not defined in

  35.    <code class="structname">pg_pltemplate</code>, but this approach is considered obsolescent.

  36.   </p><p>

  37.    When the server finds an entry in the <code class="structname">pg_pltemplate</code> catalog

  38.    for the given language name, it will use the catalog data even if the

  39.    command includes language parameters.  This behavior simplifies loading of

  40.    old dump files, which are likely to contain out-of-date information

  41.    about language support functions.

  42.   </p><p>

  43.    Ordinarily, the user must have the

  44.    <span class="productname">PostgreSQL</span> superuser privilege to

  45.    register a new language.  However, the owner of a database can register

  46.    a new language within that database if the language is listed in

  47.    the <code class="structname">pg_pltemplate</code> catalog and is marked

  48.    as allowed to be created by database owners (<code class="structfield">tmpldbacreate</code>

  49.    is true).  The default is that trusted languages can be created

  50.    by database owners, but this can be adjusted by superusers by modifying

  51.    the contents of <code class="structname">pg_pltemplate</code>.

  52.    The creator of a language becomes its owner and can later

  53.    drop it, rename it, or assign it to a new owner.

  54.   </p><p>

  55.    <code class="command">CREATE OR REPLACE LANGUAGE</code> will either create a

  56.    new language, or replace an existing definition.  If the language

  57.    already exists, its parameters are updated according to the values

  58.    specified or taken from <code class="structname">pg_pltemplate</code>,

  59.    but the language's ownership and permissions settings do not change,

  60.    and any existing functions written in the language are assumed to still

  61.    be valid.  In addition to the normal privilege requirements for creating

  62.    a language, the user must be superuser or owner of the existing language.

  63.    The <code class="literal">REPLACE</code> case is mainly meant to be used to

  64.    ensure that the language exists.  If the language has a

  65.    <code class="structname">pg_pltemplate</code> entry then <code class="literal">REPLACE</code>

  66.    will not actually change anything about an existing definition, except in

  67.    the unusual case where the <code class="structname">pg_pltemplate</code> entry

  68.    has been modified since the language was created.

  69.   </p></div><div class="refsect1" id="SQL-CREATELANGUAGE-PARAMETERS"><h2>Parameters</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">TRUSTED</code></span></dt><dd><p><code class="literal">TRUSTED</code> specifies that the language does

  70.        not grant access to data that the user would not otherwise

  71.        have.  If this key word is omitted

  72.        when registering the language, only users with the

  73.        <span class="productname">PostgreSQL</span> superuser privilege can

  74.        use this language to create new functions.

  75.       </p></dd><dt><span class="term"><code class="literal">PROCEDURAL</code></span></dt><dd><p>

  76.        This is a noise word.

  77.       </p></dd><dt><span class="term"><em class="replaceable"><code>name</code></em></span></dt><dd><p>

  78.        The name of the new procedural language.

  79.        The name must be unique among the languages in the database.

  80.       </p><p>

  81.        For backward compatibility, the name can be enclosed by single

  82.        quotes.

  83.       </p></dd><dt><span class="term"><code class="literal">HANDLER</code> <em class="replaceable"><code>call_handler</code></em></span></dt><dd><p><em class="replaceable"><code>call_handler</code></em> is

  84.        the name of a previously registered function that will be

  85.        called to execute the procedural language's functions.  The call

  86.        handler for a procedural language must be written in a compiled

  87.        language such as C with version 1 call convention and

  88.        registered with <span class="productname">PostgreSQL</span> as a

  89.        function taking no arguments and returning the

  90.        <code class="type">language_handler</code> type, a placeholder type that is

  91.        simply used to identify the function as a call handler.

  92.       </p></dd><dt><span class="term"><code class="literal">INLINE</code> <em class="replaceable"><code>inline_handler</code></em></span></dt><dd><p><em class="replaceable"><code>inline_handler</code></em> is the

  93.        name of a previously registered function that will be called

  94.        to execute an anonymous code block

  95.        (<a class="xref" href="sql-do.html" title="DO"><span class="refentrytitle">DO</span></a> command)

  96.        in this language.

  97.        If no <em class="replaceable"><code>inline_handler</code></em>

  98.        function is specified, the language does not support anonymous code

  99.        blocks.

  100.        The handler function must take one argument of

  101.        type <code class="type">internal</code>, which will be the <code class="command">DO</code> command's

  102.        internal representation, and it will typically return

  103.        <code class="type">void</code>.  The return value of the handler is ignored.

  104.       </p></dd><dt><span class="term"><code class="literal">VALIDATOR</code> <em class="replaceable"><code>valfunction</code></em></span></dt><dd><p><em class="replaceable"><code>valfunction</code></em> is the

  105.        name of a previously registered function that will be called

  106.        when a new function in the language is created, to validate the

  107.        new function.

  108.        If no

  109.        validator function is specified, then a new function will not

  110.        be checked when it is created.

  111.        The validator function must take one argument of

  112.        type <code class="type">oid</code>, which will be the OID of the

  113.        to-be-created function, and will typically return <code class="type">void</code>.

  114.       </p><p>

  115.        A validator function would typically inspect the function body

  116.        for syntactical correctness, but it can also look at other

  117.        properties of the function, for example if the language cannot

  118.        handle certain argument types.  To signal an error, the

  119.        validator function should use the <code class="function">ereport()</code>

  120.        function.  The return value of the function is ignored.

  121.       </p></dd></dl></div><p>

  122.    The <code class="literal">TRUSTED</code> option and the support function name(s) are

  123.    ignored if the server has an entry for the specified language

  124.    name in <code class="structname">pg_pltemplate</code>.

  125.   </p></div><div class="refsect1" id="SQL-CREATELANGUAGE-NOTES"><h2>Notes</h2><p>

  126.    Use <a class="xref" href="sql-droplanguage.html" title="DROP LANGUAGE"><span class="refentrytitle">DROP LANGUAGE</span></a> to drop procedural languages.

  127.   </p><p>

  128.    The system catalog <code class="classname">pg_language</code> (see <a class="xref" href="catalog-pg-language.html" title="51.29. pg_language">Section 51.29</a>) records information about the

  129.    currently installed languages.  Also, the <span class="application">psql</span>

  130.    command <code class="command">\dL</code> lists the installed languages.

  131.   </p><p>

  132.    To create functions in a procedural language, a user must have the

  133.    <code class="literal">USAGE</code> privilege for the language.  By default,

  134.    <code class="literal">USAGE</code> is granted to <code class="literal">PUBLIC</code> (i.e., everyone)

  135.    for trusted languages.  This can be revoked if desired.

  136.   </p><p>

  137.    Procedural languages are local to individual databases.

  138.    However, a language can be installed into the <code class="literal">template1</code>

  139.    database, which will cause it to be available automatically in

  140.    all subsequently-created databases.

  141.   </p><p>

  142.    The call handler function, the inline handler function (if any),

  143.    and the validator function (if any)

  144.    must already exist if the server does not have an entry for the language

  145.    in <code class="structname">pg_pltemplate</code>.  But when there is an entry,

  146.    the functions need not already exist;

  147.    they will be automatically defined if not present in the database.

  148.    (This might result in <code class="command">CREATE LANGUAGE</code> failing, if the

  149.    shared library that implements the language is not available in

  150.    the installation.)

  151.   </p><p>

  152.    In <span class="productname">PostgreSQL</span> versions before 7.3, it was

  153.    necessary to declare handler functions as returning the placeholder

  154.    type <code class="type">opaque</code>, rather than <code class="type">language_handler</code>.

  155.    To support loading

  156.    of old dump files, <code class="command">CREATE LANGUAGE</code> will accept a function

  157.    declared as returning <code class="type">opaque</code>, but it will issue a notice and

  158.    change the function's declared return type to <code class="type">language_handler</code>.

  159.   </p></div><div class="refsect1" id="SQL-CREATELANGUAGE-EXAMPLES"><h2>Examples</h2><p>

  160.    The preferred way of creating any of the standard procedural languages

  161.    is just:

  162. </p><pre class="programlisting">

  163. CREATE LANGUAGE plperl;

  164. </pre><p>

  165.   </p><p>

  166.    For a language not known in the <code class="structname">pg_pltemplate</code> catalog, a

  167.    sequence such as this is needed:

  168. </p><pre class="programlisting">

  169. CREATE FUNCTION plsample_call_handler() RETURNS language_handler

  170.     AS '$libdir/plsample'

  171.     LANGUAGE C;

  172. CREATE LANGUAGE plsample

  173.     HANDLER plsample_call_handler;

  174. </pre></div><div class="refsect1" id="SQL-CREATELANGUAGE-COMPAT"><h2>Compatibility</h2><p>

  175.    <code class="command">CREATE LANGUAGE</code> is a

  176.    <span class="productname">PostgreSQL</span> extension.

  177.   </p></div><div class="refsect1" id="id-1.9.3.70.10"><h2>See Also</h2><span class="simplelist"><a class="xref" href="sql-alterlanguage.html" title="ALTER LANGUAGE"><span class="refentrytitle">ALTER LANGUAGE</span></a>, <a class="xref" href="sql-createfunction.html" title="CREATE FUNCTION"><span class="refentrytitle">CREATE FUNCTION</span></a>, <a class="xref" href="sql-droplanguage.html" title="DROP LANGUAGE"><span class="refentrytitle">DROP LANGUAGE</span></a>, <a class="xref" href="sql-grant.html" title="GRANT"><span class="refentrytitle">GRANT</span></a>, <a class="xref" href="sql-revoke.html" title="REVOKE"><span class="refentrytitle">REVOKE</span></a></span></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="sql-createindex.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="sql-commands.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="sql-creatematerializedview.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">CREATE INDEX </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> CREATE MATERIALIZED VIEW</td></tr></table></div></body></html>
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