|
- <?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>40.6. Rules and Command Status</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="rules-privileges.html" title="40.5. Rules and Privileges" /><link rel="next" href="rules-triggers.html" title="40.7. Rules Versus Triggers" /></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">40.6. Rules and Command Status</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="rules-privileges.html" title="40.5. Rules and Privileges">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="rules.html" title="Chapter 40. The Rule System">Up</a></td><th width="60%" align="center">Chapter 40. The Rule System</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="rules-triggers.html" title="40.7. Rules Versus Triggers">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="RULES-STATUS"><div class="titlepage"><div><div><h2 class="title" style="clear: both">40.6. Rules and Command Status</h2></div></div></div><p>
- The <span class="productname">PostgreSQL</span> server returns a command
- status string, such as <code class="literal">INSERT 149592 1</code>, for each
- command it receives. This is simple enough when there are no rules
- involved, but what happens when the query is rewritten by rules?
- </p><p>
- Rules affect the command status as follows:
-
- </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
- If there is no unconditional <code class="literal">INSTEAD</code> rule for the query, then
- the originally given query will be executed, and its command
- status will be returned as usual. (But note that if there were
- any conditional <code class="literal">INSTEAD</code> rules, the negation of their qualifications
- will have been added to the original query. This might reduce the
- number of rows it processes, and if so the reported status will
- be affected.)
- </p></li><li class="listitem"><p>
- If there is any unconditional <code class="literal">INSTEAD</code> rule for the query, then
- the original query will not be executed at all. In this case,
- the server will return the command status for the last query
- that was inserted by an <code class="literal">INSTEAD</code> rule (conditional or
- unconditional) and is of the same command type
- (<code class="command">INSERT</code>, <code class="command">UPDATE</code>, or
- <code class="command">DELETE</code>) as the original query. If no query
- meeting those requirements is added by any rule, then the
- returned command status shows the original query type and
- zeroes for the row-count and OID fields.
- </p></li></ul></div><p>
- </p><p>
- The programmer can ensure that any desired <code class="literal">INSTEAD</code> rule is the one
- that sets the command status in the second case, by giving it the
- alphabetically last rule name among the active rules, so that it
- gets applied last.
- </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="rules-privileges.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="rules.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="rules-triggers.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">40.5. Rules and Privileges </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> 40.7. Rules Versus Triggers</td></tr></table></div></body></html>
|
