diff options
| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-16 19:46:48 +0000 |
|---|---|---|
| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-16 19:46:48 +0000 |
| commit | 311bcfc6b3acdd6fd152798c7f287ddf74fa2a98 (patch) | |
| tree | 0ec307299b1dada3701e42f4ca6eda57d708261e /doc/src/sgml/html/xoper.html | |
| parent | Initial commit. (diff) | |
| download | postgresql-15-311bcfc6b3acdd6fd152798c7f287ddf74fa2a98.tar.xz postgresql-15-311bcfc6b3acdd6fd152798c7f287ddf74fa2a98.zip | |
Adding upstream version 15.4.upstream/15.4upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'doc/src/sgml/html/xoper.html')
| -rw-r--r-- | doc/src/sgml/html/xoper.html | 58 |
1 files changed, 58 insertions, 0 deletions
diff --git a/doc/src/sgml/html/xoper.html b/doc/src/sgml/html/xoper.html new file mode 100644 index 0000000..52663d8 --- /dev/null +++ b/doc/src/sgml/html/xoper.html @@ -0,0 +1,58 @@ +<?xml version="1.0" encoding="UTF-8" standalone="no"?> +<!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>38.14. User-Defined Operators</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="xtypes.html" title="38.13. User-Defined Types" /><link rel="next" href="xoper-optimization.html" title="38.15. Operator Optimization Information" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">38.14. User-Defined Operators</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="xtypes.html" title="38.13. User-Defined Types">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="extend.html" title="Chapter 38. Extending SQL">Up</a></td><th width="60%" align="center">Chapter 38. Extending <acronym class="acronym">SQL</acronym></th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 15.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="xoper-optimization.html" title="38.15. Operator Optimization Information">Next</a></td></tr></table><hr /></div><div class="sect1" id="XOPER"><div class="titlepage"><div><div><h2 class="title" style="clear: both">38.14. User-Defined Operators</h2></div></div></div><a id="id-1.8.3.17.2" class="indexterm"></a><p> + Every operator is <span class="quote">“<span class="quote">syntactic sugar</span>”</span> for a call to an + underlying function that does the real work; so you must + first create the underlying function before you can create + the operator. However, an operator is <span class="emphasis"><em>not merely</em></span> + syntactic sugar, because it carries additional information + that helps the query planner optimize queries that use the + operator. The next section will be devoted to explaining + that additional information. + </p><p> + <span class="productname">PostgreSQL</span> supports prefix + and infix operators. Operators can be + overloaded;<a id="id-1.8.3.17.4.2" class="indexterm"></a> + that is, the same operator name can be used for different operators + that have different numbers and types of operands. When a query is + executed, the system determines the operator to call from the + number and types of the provided operands. + </p><p> + Here is an example of creating an operator for adding two complex + numbers. We assume we've already created the definition of type + <code class="type">complex</code> (see <a class="xref" href="xtypes.html" title="38.13. User-Defined Types">Section 38.13</a>). First we need a + function that does the work, then we can define the operator: + +</p><pre class="programlisting"> +CREATE FUNCTION complex_add(complex, complex) + RETURNS complex + AS '<em class="replaceable"><code>filename</code></em>', 'complex_add' + LANGUAGE C IMMUTABLE STRICT; + +CREATE OPERATOR + ( + leftarg = complex, + rightarg = complex, + function = complex_add, + commutator = + +); +</pre><p> + </p><p> + Now we could execute a query like this: + +</p><pre class="screen"> +SELECT (a + b) AS c FROM test_complex; + + c +----------------- + (5.2,6.05) + (133.42,144.95) +</pre><p> + </p><p> + We've shown how to create a binary operator here. To create a prefix + operator, just omit the <code class="literal">leftarg</code>. + The <code class="literal">function</code> + clause and the argument clauses are the only required items in + <code class="command">CREATE OPERATOR</code>. The <code class="literal">commutator</code> + clause shown in the example is an optional hint to the query + optimizer. Further details about <code class="literal">commutator</code> and other + optimizer hints appear in the next section. + </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="xtypes.html" title="38.13. User-Defined Types">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="extend.html" title="Chapter 38. Extending SQL">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="xoper-optimization.html" title="38.15. Operator Optimization Information">Next</a></td></tr><tr><td width="40%" align="left" valign="top">38.13. User-Defined Types </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.4 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 38.15. Operator Optimization Information</td></tr></table></div></body></html>
\ No newline at end of file |