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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 48. Logical Decoding</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="bgworker.html" title="Chapter 47. Background Worker Processes" /><link rel="next" href="logicaldecoding-example.html" title="48.1. Logical Decoding Examples" /></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 48. Logical Decoding</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="bgworker.html" title="Chapter 47. Background Worker Processes">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="logicaldecoding-example.html" title="48.1. Logical Decoding Examples">Next</a></td></tr></table><hr></hr></div><div class="chapter" id="LOGICALDECODING"><div class="titlepage"><div><div><h2 class="title">Chapter 48. Logical Decoding</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl class="toc"><dt><span class="sect1"><a href="logicaldecoding-example.html">48.1. Logical Decoding Examples</a></span></dt><dt><span class="sect1"><a href="logicaldecoding-explanation.html">48.2. Logical Decoding Concepts</a></span></dt><dd><dl><dt><span class="sect2"><a href="logicaldecoding-explanation.html#id-1.8.14.8.2">48.2.1. Logical Decoding</a></span></dt><dt><span class="sect2"><a href="logicaldecoding-explanation.html#LOGICALDECODING-REPLICATION-SLOTS">48.2.2. Replication Slots</a></span></dt><dt><span class="sect2"><a href="logicaldecoding-explanation.html#id-1.8.14.8.4">48.2.3. Output Plugins</a></span></dt><dt><span class="sect2"><a href="logicaldecoding-explanation.html#id-1.8.14.8.5">48.2.4. Exported Snapshots</a></span></dt></dl></dd><dt><span class="sect1"><a href="logicaldecoding-walsender.html">48.3. Streaming Replication Protocol Interface</a></span></dt><dt><span class="sect1"><a href="logicaldecoding-sql.html">48.4. Logical Decoding <acronym class="acronym">SQL</acronym> Interface</a></span></dt><dt><span class="sect1"><a href="logicaldecoding-catalogs.html">48.5. System Catalogs Related to Logical Decoding</a></span></dt><dt><span class="sect1"><a href="logicaldecoding-output-plugin.html">48.6. Logical Decoding Output Plugins</a></span></dt><dd><dl><dt><span class="sect2"><a href="logicaldecoding-output-plugin.html#LOGICALDECODING-OUTPUT-INIT">48.6.1. Initialization Function</a></span></dt><dt><span class="sect2"><a href="logicaldecoding-output-plugin.html#LOGICALDECODING-CAPABILITIES">48.6.2. Capabilities</a></span></dt><dt><span class="sect2"><a href="logicaldecoding-output-plugin.html#LOGICALDECODING-OUTPUT-MODE">48.6.3. Output Modes</a></span></dt><dt><span class="sect2"><a href="logicaldecoding-output-plugin.html#LOGICALDECODING-OUTPUT-PLUGIN-CALLBACKS">48.6.4. Output Plugin Callbacks</a></span></dt><dt><span class="sect2"><a href="logicaldecoding-output-plugin.html#LOGICALDECODING-OUTPUT-PLUGIN-OUTPUT">48.6.5. Functions for Producing Output</a></span></dt></dl></dd><dt><span class="sect1"><a href="logicaldecoding-writer.html">48.7. Logical Decoding Output Writers</a></span></dt><dt><span class="sect1"><a href="logicaldecoding-synchronous.html">48.8. Synchronous Replication Support for Logical Decoding</a></span></dt></dl></div><a id="id-1.8.14.2" class="indexterm"></a><p>
- PostgreSQL provides infrastructure to stream the modifications performed
- via SQL to external consumers. This functionality can be used for a
- variety of purposes, including replication solutions and auditing.
- </p><p>
- Changes are sent out in streams identified by logical replication slots.
- </p><p>
- The format in which those changes are streamed is determined by the output
- plugin used. An example plugin is provided in the PostgreSQL distribution.
- Additional plugins can be
- written to extend the choice of available formats without modifying any
- core code.
- Every output plugin has access to each individual new row produced
- by <code class="command">INSERT</code> and the new row version created
- by <code class="command">UPDATE</code>. Availability of old row versions for
- <code class="command">UPDATE</code> and <code class="command">DELETE</code> depends on
- the configured replica identity (see <a class="xref" href="sql-altertable.html#SQL-CREATETABLE-REPLICA-IDENTITY"><code class="literal">REPLICA IDENTITY</code></a>).
- </p><p>
- Changes can be consumed either using the streaming replication protocol
- (see <a class="xref" href="protocol-replication.html" title="52.4. Streaming Replication Protocol">Section 52.4</a> and
- <a class="xref" href="logicaldecoding-walsender.html" title="48.3. Streaming Replication Protocol Interface">Section 48.3</a>), or by calling functions
- via SQL (see <a class="xref" href="logicaldecoding-sql.html" title="48.4. Logical Decoding SQL Interface">Section 48.4</a>). It is also possible
- to write additional methods of consuming the output of a replication slot
- without modifying core code
- (see <a class="xref" href="logicaldecoding-writer.html" title="48.7. Logical Decoding Output Writers">Section 48.7</a>).
- </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bgworker.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="logicaldecoding-example.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 47. Background Worker Processes </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> 48.1. Logical Decoding Examples</td></tr></table></div></body></html>
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