1 files changed, 31 insertions, 2 deletions
diff --git a/doc/src/sgml/html/indexes-intro.html b/doc/src/sgml/html/indexes-intro.html
index acdb0c6..2dadf9a 100644
--- a/doc/src/sgml/html/indexes-intro.html
+++ b/doc/src/sgml/html/indexes-intro.html
@@ -1,5 +1,5 @@
 <?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>11.1. Introduction</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="indexes.html" title="Chapter 11. Indexes" /><link rel="next" href="indexes-types.html" title="11.2. Index Types" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">11.1. Introduction</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="indexes.html" title="Chapter 11. Indexes">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 15.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="indexes-types.html" title="11.2. Index Types">Next</a></td></tr></table><hr /></div><div class="sect1" id="INDEXES-INTRO"><div class="titlepage"><div><div><h2 class="title" style="clear: both">11.1. Introduction</h2></div></div></div><p>
+<!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>11.1. Introduction</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="indexes.html" title="Chapter 11. Indexes" /><link rel="next" href="indexes-types.html" title="11.2. Index Types" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">11.1. Introduction</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="indexes.html" title="Chapter 11. Indexes">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 15.6 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="indexes-types.html" title="11.2. Index Types">Next</a></td></tr></table><hr /></div><div class="sect1" id="INDEXES-INTRO"><div class="titlepage"><div><div><h2 class="title" style="clear: both">11.1. Introduction</h2></div></div></div><p>
    Suppose we have a table similar to this:
 </p><pre class="programlisting">
 CREATE TABLE test1 (
@@ -59,6 +59,35 @@ CREATE INDEX test1_id_index ON test1 (id);
    an index defined on a column that is part of a join condition can
    also significantly speed up queries with joins.
   </p><p>
+   In general, <span class="productname">PostgreSQL</span> indexes can be used
+   to optimize queries that contain one or more <code class="literal">WHERE</code>
+   or <code class="literal">JOIN</code> clauses of the form
+
+</p><pre class="synopsis">
+<em class="replaceable"><code>indexed-column</code></em> <em class="replaceable"><code>indexable-operator</code></em> <em class="replaceable"><code>comparison-value</code></em>
+</pre><p>
+
+   Here, the <em class="replaceable"><code>indexed-column</code></em> is whatever
+   column or expression the index has been defined on.
+   The <em class="replaceable"><code>indexable-operator</code></em> is an operator that
+   is a member of the index's <em class="firstterm">operator class</em> for
+   the indexed column.  (More details about that appear below.)
+   And the <em class="replaceable"><code>comparison-value</code></em> can be any
+   expression that is not volatile and does not reference the index's
+   table.
+  </p><p>
+   In some cases the query planner can extract an indexable clause of
+   this form from another SQL construct.  A simple example is that if
+   the original clause was
+
+</p><pre class="synopsis">
+<em class="replaceable"><code>comparison-value</code></em> <em class="replaceable"><code>operator</code></em> <em class="replaceable"><code>indexed-column</code></em>
+</pre><p>
+
+   then it can be flipped around into indexable form if the
+   original <em class="replaceable"><code>operator</code></em> has a commutator
+   operator that is a member of the index's operator class.
+  </p><p>
    Creating an index on a large table can take a long time.  By default,
    <span class="productname">PostgreSQL</span> allows reads (<code class="command">SELECT</code> statements) to occur
    on the table in parallel with index creation, but writes (<code class="command">INSERT</code>,
@@ -74,4 +103,4 @@ CREATE INDEX test1_id_index ON test1 (id);
    tuples</a>.
    Therefore indexes that are seldom or never used in queries
    should be removed.
-  </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="indexes.html" title="Chapter 11. Indexes">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-types.html" title="11.2. Index Types">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 11. Indexes </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.5 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 11.2. Index Types</td></tr></table></div></body></html>
-\ No newline at end of file
+  </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="indexes.html" title="Chapter 11. Indexes">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-types.html" title="11.2. Index Types">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 11. Indexes </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.6 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 11.2. Index Types</td></tr></table></div></body></html>
+\ No newline at end of file