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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-04 12:19:15 +0000 |
|---|---|---|
| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-04 12:19:15 +0000 |
| commit | 6eb9c5a5657d1fe77b55cc261450f3538d35a94d (patch) | |
| tree | 657d8194422a5daccecfd42d654b8a245ef7b4c8 /doc/src/sgml/html/indexes-collations.html | |
| parent | Initial commit. (diff) | |
| download | postgresql-13-upstream.tar.xz postgresql-13-upstream.zip | |
Adding upstream version 13.4.upstream/13.4upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'doc/src/sgml/html/indexes-collations.html')
| -rw-r--r-- | doc/src/sgml/html/indexes-collations.html | 31 |
1 files changed, 31 insertions, 0 deletions
diff --git a/doc/src/sgml/html/indexes-collations.html b/doc/src/sgml/html/indexes-collations.html new file mode 100644 index 0000000..68daa63 --- /dev/null +++ b/doc/src/sgml/html/indexes-collations.html @@ -0,0 +1,31 @@ +<?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>11.11. Indexes and Collations</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="indexes-opclass.html" title="11.10. Operator Classes and Operator Families" /><link rel="next" href="indexes-examine.html" title="11.12. Examining Index Usage" /></head><body id="docContent" class="container-fluid col-10"><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">11.11. Indexes and Collations</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="indexes-opclass.html" title="11.10. Operator Classes and Operator Families">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="indexes.html" title="Chapter 11. Indexes">Up</a></td><th width="60%" align="center">Chapter 11. Indexes</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 13.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="indexes-examine.html" title="11.12. Examining Index Usage">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="INDEXES-COLLATIONS"><div class="titlepage"><div><div><h2 class="title" style="clear: both">11.11. Indexes and Collations</h2></div></div></div><p> + An index can support only one collation per index column. + If multiple collations are of interest, multiple indexes may be needed. + </p><p> + Consider these statements: +</p><pre class="programlisting"> +CREATE TABLE test1c ( + id integer, + content varchar COLLATE "x" +); + +CREATE INDEX test1c_content_index ON test1c (content); +</pre><p> + The index automatically uses the collation of the + underlying column. So a query of the form +</p><pre class="programlisting"> +SELECT * FROM test1c WHERE content > <em class="replaceable"><code>constant</code></em>; +</pre><p> + could use the index, because the comparison will by default use the + collation of the column. However, this index cannot accelerate queries + that involve some other collation. So if queries of the form, say, +</p><pre class="programlisting"> +SELECT * FROM test1c WHERE content > <em class="replaceable"><code>constant</code></em> COLLATE "y"; +</pre><p> + are also of interest, an additional index could be created that supports + the <code class="literal">"y"</code> collation, like this: +</p><pre class="programlisting"> +CREATE INDEX test1c_content_y_index ON test1c (content COLLATE "y"); +</pre><p> + </p></div><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navfooter"><hr></hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="indexes-opclass.html" title="11.10. Operator Classes and Operator Families">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="indexes.html" title="Chapter 11. Indexes">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="indexes-examine.html" title="11.12. Examining Index Usage">Next</a></td></tr><tr><td width="40%" align="left" valign="top">11.10. Operator Classes and Operator Families </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 13.4 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 11.12. Examining Index Usage</td></tr></table></div></body></html>
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