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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>F.36. spi</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="sepgsql.html" title="F.35. sepgsql" /><link rel="next" href="sslinfo.html" title="F.37. sslinfo" /></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">F.36. spi</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="sepgsql.html" title="F.35. sepgsql">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="contrib.html" title="Appendix F. Additional Supplied Modules">Up</a></td><th width="60%" align="center">Appendix F. Additional Supplied Modules</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="sslinfo.html" title="F.37. sslinfo">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="CONTRIB-SPI"><div class="titlepage"><div><div><h2 class="title" style="clear: both">F.36. spi</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="contrib-spi.html#id-1.11.7.45.5">F.36.1. refint — Functions for Implementing Referential Integrity</a></span></dt><dt><span class="sect2"><a href="contrib-spi.html#id-1.11.7.45.6">F.36.2. autoinc — Functions for Autoincrementing Fields</a></span></dt><dt><span class="sect2"><a href="contrib-spi.html#id-1.11.7.45.7">F.36.3. insert_username — Functions for Tracking Who Changed a Table</a></span></dt><dt><span class="sect2"><a href="contrib-spi.html#id-1.11.7.45.8">F.36.4. moddatetime — Functions for Tracking Last Modification Time</a></span></dt></dl></div><a id="id-1.11.7.45.2" class="indexterm"></a><p>
- The <span class="application">spi</span> module provides several workable examples
- of using the <a class="link" href="spi.html" title="Chapter 46. Server Programming Interface">Server Programming Interface</a>
- (<acronym class="acronym">SPI</acronym>) and triggers. While these functions are of
- some value in
- their own right, they are even more useful as examples to modify for
- your own purposes. The functions are general enough to be used
- with any table, but you have to specify table and field names (as described
- below) while creating a trigger.
- </p><p>
- Each of the groups of functions described below is provided as a
- separately-installable extension.
- </p><div class="sect2" id="id-1.11.7.45.5"><div class="titlepage"><div><div><h3 class="title">F.36.1. refint — Functions for Implementing Referential Integrity</h3></div></div></div><p>
- <code class="function">check_primary_key()</code> and
- <code class="function">check_foreign_key()</code> are used to check foreign key constraints.
- (This functionality is long since superseded by the built-in foreign
- key mechanism, of course, but the module is still useful as an example.)
- </p><p>
- <code class="function">check_primary_key()</code> checks the referencing table.
- To use, create a <code class="literal">BEFORE INSERT OR UPDATE</code> trigger using this
- function on a table referencing another table. Specify as the trigger
- arguments: the referencing table's column name(s) which form the foreign
- key, the referenced table name, and the column names in the referenced table
- which form the primary/unique key. To handle multiple foreign
- keys, create a trigger for each reference.
- </p><p>
- <code class="function">check_foreign_key()</code> checks the referenced table.
- To use, create a <code class="literal">BEFORE DELETE OR UPDATE</code> trigger using this
- function on a table referenced by other table(s). Specify as the trigger
- arguments: the number of referencing tables for which the function has to
- perform checking, the action if a referencing key is found
- (<code class="literal">cascade</code> — to delete the referencing row,
- <code class="literal">restrict</code> — to abort transaction if referencing keys
- exist, <code class="literal">setnull</code> — to set referencing key fields to null),
- the triggered table's column names which form the primary/unique key, then
- the referencing table name and column names (repeated for as many
- referencing tables as were specified by first argument). Note that the
- primary/unique key columns should be marked NOT NULL and should have a
- unique index.
- </p><p>
- There are examples in <code class="filename">refint.example</code>.
- </p></div><div class="sect2" id="id-1.11.7.45.6"><div class="titlepage"><div><div><h3 class="title">F.36.2. autoinc — Functions for Autoincrementing Fields</h3></div></div></div><p>
- <code class="function">autoinc()</code> is a trigger that stores the next value of
- a sequence into an integer field. This has some overlap with the
- built-in <span class="quote">“<span class="quote">serial column</span>”</span> feature, but it is not the same:
- <code class="function">autoinc()</code> will override attempts to substitute a
- different field value during inserts, and optionally it can be
- used to increment the field during updates, too.
- </p><p>
- To use, create a <code class="literal">BEFORE INSERT</code> (or optionally <code class="literal">BEFORE
- INSERT OR UPDATE</code>) trigger using this function. Specify two
- trigger arguments: the name of the integer column to be modified,
- and the name of the sequence object that will supply values.
- (Actually, you can specify any number of pairs of such names, if
- you'd like to update more than one autoincrementing column.)
- </p><p>
- There is an example in <code class="filename">autoinc.example</code>.
- </p></div><div class="sect2" id="id-1.11.7.45.7"><div class="titlepage"><div><div><h3 class="title">F.36.3. insert_username — Functions for Tracking Who Changed a Table</h3></div></div></div><p>
- <code class="function">insert_username()</code> is a trigger that stores the current
- user's name into a text field. This can be useful for tracking
- who last modified a particular row within a table.
- </p><p>
- To use, create a <code class="literal">BEFORE INSERT</code> and/or <code class="literal">UPDATE</code>
- trigger using this function. Specify a single trigger
- argument: the name of the text column to be modified.
- </p><p>
- There is an example in <code class="filename">insert_username.example</code>.
- </p></div><div class="sect2" id="id-1.11.7.45.8"><div class="titlepage"><div><div><h3 class="title">F.36.4. moddatetime — Functions for Tracking Last Modification Time</h3></div></div></div><p>
- <code class="function">moddatetime()</code> is a trigger that stores the current
- time into a <code class="type">timestamp</code> field. This can be useful for tracking
- the last modification time of a particular row within a table.
- </p><p>
- To use, create a <code class="literal">BEFORE UPDATE</code>
- trigger using this function. Specify a single trigger
- argument: the name of the column to be modified.
- The column must be of type <code class="type">timestamp</code> or <code class="type">timestamp with
- time zone</code>.
- </p><p>
- There is an example in <code class="filename">moddatetime.example</code>.
- </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="sepgsql.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="contrib.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="sslinfo.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">F.35. sepgsql </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> F.37. sslinfo</td></tr></table></div></body></html>
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