diff options
Diffstat (limited to '')
| -rw-r--r-- | doc/src/sgml/html/rule-system.html | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/doc/src/sgml/html/rule-system.html b/doc/src/sgml/html/rule-system.html new file mode 100644 index 0000000..b7d32e0 --- /dev/null +++ b/doc/src/sgml/html/rule-system.html @@ -0,0 +1,30 @@ +<?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>52.4. The PostgreSQL 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 Vsnapshot" /><link rel="prev" href="parser-stage.html" title="52.3. The Parser Stage" /><link rel="next" href="planner-optimizer.html" title="52.5. Planner/Optimizer" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">52.4. The <span class="productname">PostgreSQL</span> Rule System</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="parser-stage.html" title="52.3. The Parser Stage">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="overview.html" title="Chapter 52. Overview of PostgreSQL Internals">Up</a></td><th width="60%" align="center">Chapter 52. Overview of PostgreSQL Internals</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 16.2 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="planner-optimizer.html" title="52.5. Planner/Optimizer">Next</a></td></tr></table><hr /></div><div class="sect1" id="RULE-SYSTEM"><div class="titlepage"><div><div><h2 class="title" style="clear: both">52.4. The <span class="productname">PostgreSQL</span> Rule System <a href="#RULE-SYSTEM" class="id_link">#</a></h2></div></div></div><p> + <span class="productname">PostgreSQL</span> supports a powerful + <em class="firstterm">rule system</em> for the specification + of <em class="firstterm">views</em> and ambiguous <em class="firstterm">view updates</em>. + Originally the <span class="productname">PostgreSQL</span> + rule system consisted of two implementations: + + </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p> + The first one worked using <em class="firstterm">row level</em> processing and was + implemented deep in the <em class="firstterm">executor</em>. The rule system was + called whenever an individual row had been accessed. This + implementation was removed in 1995 when the last official release + of the <span class="productname">Berkeley Postgres</span> project was + transformed into <span class="productname">Postgres95</span>. + </p></li><li class="listitem"><p> + The second implementation of the rule system is a technique + called <em class="firstterm">query rewriting</em>. + The <em class="firstterm">rewrite system</em> is a module + that exists between the <em class="firstterm">parser stage</em> and the + <em class="firstterm">planner/optimizer</em>. This technique is still implemented. + </p></li></ul></div><p> + </p><p> + The query rewriter is discussed in some detail in + <a class="xref" href="rules.html" title="Chapter 41. The Rule System">Chapter 41</a>, so there is no need to cover it here. + We will only point out that both the input and the output of the + rewriter are query trees, that is, there is no change in the + representation or level of semantic detail in the trees. Rewriting + can be thought of as a form of macro expansion. + </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="parser-stage.html" title="52.3. The Parser Stage">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="overview.html" title="Chapter 52. Overview of PostgreSQL Internals">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="planner-optimizer.html" title="52.5. Planner/Optimizer">Next</a></td></tr><tr><td width="40%" align="left" valign="top">52.3. The Parser Stage </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 16.2 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 52.5. Planner/Optimizer</td></tr></table></div></body></html>
\ No newline at end of file |