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- <!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>Chapter 40. The Rule System</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="event-trigger-table-rewrite-example.html" title="39.5. A Table Rewrite Event Trigger Example" /><link rel="next" href="querytree.html" title="40.1. The Query Tree" /></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">Chapter 40. The Rule System</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="event-trigger-table-rewrite-example.html" title="39.5. A Table Rewrite Event Trigger Example">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="server-programming.html" title="Part V. Server Programming">Up</a></td><th width="60%" align="center">Part V. Server Programming</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="querytree.html" title="40.1. The Query Tree">Next</a></td></tr></table><hr></hr></div><div class="chapter" id="RULES"><div class="titlepage"><div><div><h2 class="title">Chapter 40. The Rule System</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl class="toc"><dt><span class="sect1"><a href="querytree.html">40.1. The Query Tree</a></span></dt><dt><span class="sect1"><a href="rules-views.html">40.2. Views and the Rule System</a></span></dt><dd><dl><dt><span class="sect2"><a href="rules-views.html#RULES-SELECT">40.2.1. How <code class="command">SELECT</code> Rules Work</a></span></dt><dt><span class="sect2"><a href="rules-views.html#id-1.8.6.7.6">40.2.2. View Rules in Non-<code class="command">SELECT</code> Statements</a></span></dt><dt><span class="sect2"><a href="rules-views.html#id-1.8.6.7.7">40.2.3. The Power of Views in <span class="productname">PostgreSQL</span></a></span></dt><dt><span class="sect2"><a href="rules-views.html#RULES-VIEWS-UPDATE">40.2.4. Updating a View</a></span></dt></dl></dd><dt><span class="sect1"><a href="rules-materializedviews.html">40.3. Materialized Views</a></span></dt><dt><span class="sect1"><a href="rules-update.html">40.4. Rules on <code class="command">INSERT</code>, <code class="command">UPDATE</code>, and <code class="command">DELETE</code></a></span></dt><dd><dl><dt><span class="sect2"><a href="rules-update.html#id-1.8.6.9.7">40.4.1. How Update Rules Work</a></span></dt><dt><span class="sect2"><a href="rules-update.html#RULES-UPDATE-VIEWS">40.4.2. Cooperation with Views</a></span></dt></dl></dd><dt><span class="sect1"><a href="rules-privileges.html">40.5. Rules and Privileges</a></span></dt><dt><span class="sect1"><a href="rules-status.html">40.6. Rules and Command Status</a></span></dt><dt><span class="sect1"><a href="rules-triggers.html">40.7. Rules Versus Triggers</a></span></dt></dl></div><a id="id-1.8.6.2" class="indexterm"></a><p>
- This chapter discusses the rule system in
- <span class="productname">PostgreSQL</span>. Production rule systems
- are conceptually simple, but there are many subtle points
- involved in actually using them.
- </p><p>
- Some other database systems define active database rules, which
- are usually stored procedures and triggers. In
- <span class="productname">PostgreSQL</span>, these can be implemented
- using functions and triggers as well.
- </p><p>
- The rule system (more precisely speaking, the query rewrite rule
- system) is totally different from stored procedures and triggers.
- It modifies queries to take rules into consideration, and then
- passes the modified query to the query planner for planning and
- execution. It is very powerful, and can be used for many things
- such as query language procedures, views, and versions. The
- theoretical foundations and the power of this rule system are
- also discussed in <a class="xref" href="biblio.html#STON90B">[ston90b]</a> and <a class="xref" href="biblio.html#ONG90">[ong90]</a>.
- </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="event-trigger-table-rewrite-example.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="server-programming.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="querytree.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">39.5. A Table Rewrite Event Trigger Example </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> 40.1. The Query Tree</td></tr></table></div></body></html>
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