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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 31. Logical Replication</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="wal-internals.html" title="30.6. WAL Internals" /><link rel="next" href="logical-replication-publication.html" title="31.1. Publication" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">Chapter 31. Logical Replication</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="wal-internals.html" title="30.6. WAL Internals">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="admin.html" title="Part III. Server Administration">Up</a></td><th width="60%" align="center">Part III. Server Administration</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 15.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="logical-replication-publication.html" title="31.1. Publication">Next</a></td></tr></table><hr /></div><div class="chapter" id="LOGICAL-REPLICATION"><div class="titlepage"><div><div><h2 class="title">Chapter 31. Logical Replication</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl class="toc"><dt><span class="sect1"><a href="logical-replication-publication.html">31.1. Publication</a></span></dt><dt><span class="sect1"><a href="logical-replication-subscription.html">31.2. Subscription</a></span></dt><dd><dl><dt><span class="sect2"><a href="logical-replication-subscription.html#LOGICAL-REPLICATION-SUBSCRIPTION-SLOT">31.2.1. Replication Slot Management</a></span></dt><dt><span class="sect2"><a href="logical-replication-subscription.html#LOGICAL-REPLICATION-SUBSCRIPTION-EXAMPLES">31.2.2. Examples</a></span></dt></dl></dd><dt><span class="sect1"><a href="logical-replication-row-filter.html">31.3. Row Filters</a></span></dt><dd><dl><dt><span class="sect2"><a href="logical-replication-row-filter.html#LOGICAL-REPLICATION-ROW-FILTER-RULES">31.3.1. Row Filter Rules</a></span></dt><dt><span class="sect2"><a href="logical-replication-row-filter.html#LOGICAL-REPLICATION-ROW-FILTER-RESTRICTIONS">31.3.2. Expression Restrictions</a></span></dt><dt><span class="sect2"><a href="logical-replication-row-filter.html#LOGICAL-REPLICATION-ROW-FILTER-TRANSFORMATIONS">31.3.3. UPDATE Transformations</a></span></dt><dt><span class="sect2"><a href="logical-replication-row-filter.html#LOGICAL-REPLICATION-ROW-FILTER-PARTITIONED-TABLE">31.3.4. Partitioned Tables</a></span></dt><dt><span class="sect2"><a href="logical-replication-row-filter.html#LOGICAL-REPLICATION-ROW-FILTER-INITIAL-DATA-SYNC">31.3.5. Initial Data Synchronization</a></span></dt><dt><span class="sect2"><a href="logical-replication-row-filter.html#LOGICAL-REPLICATION-ROW-FILTER-COMBINING">31.3.6. Combining Multiple Row Filters</a></span></dt><dt><span class="sect2"><a href="logical-replication-row-filter.html#LOGICAL-REPLICATION-ROW-FILTER-EXAMPLES">31.3.7. Examples</a></span></dt></dl></dd><dt><span class="sect1"><a href="logical-replication-col-lists.html">31.4. Column Lists</a></span></dt><dd><dl><dt><span class="sect2"><a href="logical-replication-col-lists.html#LOGICAL-REPLICATION-COL-LIST-EXAMPLES">31.4.1. Examples</a></span></dt></dl></dd><dt><span class="sect1"><a href="logical-replication-conflicts.html">31.5. Conflicts</a></span></dt><dt><span class="sect1"><a href="logical-replication-restrictions.html">31.6. Restrictions</a></span></dt><dt><span class="sect1"><a href="logical-replication-architecture.html">31.7. Architecture</a></span></dt><dd><dl><dt><span class="sect2"><a href="logical-replication-architecture.html#LOGICAL-REPLICATION-SNAPSHOT">31.7.1. Initial Snapshot</a></span></dt></dl></dd><dt><span class="sect1"><a href="logical-replication-monitoring.html">31.8. Monitoring</a></span></dt><dt><span class="sect1"><a href="logical-replication-security.html">31.9. Security</a></span></dt><dt><span class="sect1"><a href="logical-replication-config.html">31.10. Configuration Settings</a></span></dt><dt><span class="sect1"><a href="logical-replication-quick-setup.html">31.11. Quick Setup</a></span></dt></dl></div><p>
+ Logical replication is a method of replicating data objects and their
+ changes, based upon their replication identity (usually a primary key). We
+ use the term logical in contrast to physical replication, which uses exact
+ block addresses and byte-by-byte replication. PostgreSQL supports both
+ mechanisms concurrently, see <a class="xref" href="high-availability.html" title="Chapter 27. High Availability, Load Balancing, and Replication">Chapter 27</a>. Logical
+ replication allows fine-grained control over both data replication and
+ security.
+ </p><p>
+ Logical replication uses a <em class="firstterm">publish</em>
+ and <em class="firstterm">subscribe</em> model with one or
+ more <em class="firstterm">subscribers</em> subscribing to one or more
+ <em class="firstterm">publications</em> on a <em class="firstterm">publisher</em>
+ node. Subscribers pull data from the publications they subscribe to and may
+ subsequently re-publish data to allow cascading replication or more complex
+ configurations.
+ </p><p>
+ Logical replication of a table typically starts with taking a snapshot
+ of the data on the publisher database and copying that to the subscriber.
+ Once that is done, the changes on the publisher are sent to the subscriber
+ as they occur in real-time. The subscriber applies the data in the same
+ order as the publisher so that transactional consistency is guaranteed for
+ publications within a single subscription. This method of data replication
+ is sometimes referred to as transactional replication.
+ </p><p>
+ The typical use-cases for logical replication are:
+
+ </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
+ Sending incremental changes in a single database or a subset of a
+ database to subscribers as they occur.
+ </p></li><li class="listitem"><p>
+ Firing triggers for individual changes as they arrive on the
+ subscriber.
+ </p></li><li class="listitem"><p>
+ Consolidating multiple databases into a single one (for example for
+ analytical purposes).
+ </p></li><li class="listitem"><p>
+ Replicating between different major versions of PostgreSQL.
+ </p></li><li class="listitem"><p>
+ Replicating between PostgreSQL instances on different platforms (for
+ example Linux to Windows)
+ </p></li><li class="listitem"><p>
+ Giving access to replicated data to different groups of users.
+ </p></li><li class="listitem"><p>
+ Sharing a subset of the database between multiple databases.
+ </p></li></ul></div><p>
+ </p><p>
+ The subscriber database behaves in the same way as any other PostgreSQL
+ instance and can be used as a publisher for other databases by defining its
+ own publications. When the subscriber is treated as read-only by
+ application, there will be no conflicts from a single subscription. On the
+ other hand, if there are other writes done either by an application or by other
+ subscribers to the same set of tables, conflicts can arise.
+ </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="wal-internals.html" title="30.6. WAL Internals">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="admin.html" title="Part III. Server Administration">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="logical-replication-publication.html" title="31.1. Publication">Next</a></td></tr><tr><td width="40%" align="left" valign="top">30.6. WAL Internals </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.5 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 31.1. Publication</td></tr></table></div></body></html> \ No newline at end of file