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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>31.6. Restrictions</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="logical-replication-conflicts.html" title="31.5. Conflicts" /><link rel="next" href="logical-replication-architecture.html" title="31.7. Architecture" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">31.6. Restrictions</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="logical-replication-conflicts.html" title="31.5. Conflicts">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="logical-replication.html" title="Chapter 31. Logical Replication">Up</a></td><th width="60%" align="center">Chapter 31. Logical Replication</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 15.6 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="logical-replication-architecture.html" title="31.7. Architecture">Next</a></td></tr></table><hr /></div><div class="sect1" id="LOGICAL-REPLICATION-RESTRICTIONS"><div class="titlepage"><div><div><h2 class="title" style="clear: both">31.6. Restrictions</h2></div></div></div><p>
   Logical replication currently has the following restrictions or missing
   functionality.  These might be addressed in future releases.
  </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
     The database schema and DDL commands are not replicated.  The initial
     schema can be copied by hand using <code class="literal">pg_dump
     --schema-only</code>.  Subsequent schema changes would need to be kept
     in sync manually.  (Note, however, that there is no need for the schemas
     to be absolutely the same on both sides.)  Logical replication is robust
     when schema definitions change in a live database: When the schema is
     changed on the publisher and replicated data starts arriving at the
     subscriber but does not fit into the table schema, replication will error
     until the schema is updated.  In many cases, intermittent errors can be
     avoided by applying additive schema changes to the subscriber first.
    </p></li><li class="listitem"><p>
     Sequence data is not replicated.  The data in serial or identity columns
     backed by sequences will of course be replicated as part of the table,
     but the sequence itself would still show the start value on the
     subscriber.  If the subscriber is used as a read-only database, then this
     should typically not be a problem.  If, however, some kind of switchover
     or failover to the subscriber database is intended, then the sequences
     would need to be updated to the latest values, either by copying the
     current data from the publisher (perhaps
     using <code class="command">pg_dump</code>) or by determining a sufficiently high
     value from the tables themselves.
    </p></li><li class="listitem"><p>
     Replication of <code class="command">TRUNCATE</code> commands is supported, but
     some care must be taken when truncating groups of tables connected by
     foreign keys.  When replicating a truncate action, the subscriber will
     truncate the same group of tables that was truncated on the publisher,
     either explicitly specified or implicitly collected via
     <code class="literal">CASCADE</code>, minus tables that are not part of the
     subscription.  This will work correctly if all affected tables are part
     of the same subscription.  But if some tables to be truncated on the
     subscriber have foreign-key links to tables that are not part of the same
     (or any) subscription, then the application of the truncate action on the
     subscriber will fail.
    </p></li><li class="listitem"><p>
     Large objects (see <a class="xref" href="largeobjects.html" title="Chapter 35. Large Objects">Chapter 35</a>) are not replicated.
     There is no workaround for that, other than storing data in normal
     tables.
    </p></li><li class="listitem"><p>
     Replication is only supported by tables, including partitioned tables.
     Attempts to replicate other types of relations, such as views, materialized
     views, or foreign tables, will result in an error.
    </p></li><li class="listitem"><p>
     When replicating between partitioned tables, the actual replication
     originates, by default, from the leaf partitions on the publisher, so
     partitions on the publisher must also exist on the subscriber as valid
     target tables. (They could either be leaf partitions themselves, or they
     could be further subpartitioned, or they could even be independent
     tables.)  Publications can also specify that changes are to be replicated
     using the identity and schema of the partitioned root table instead of
     that of the individual leaf partitions in which the changes actually
     originate (see <a class="link" href="sql-createpublication.html" title="CREATE PUBLICATION"><code class="command">CREATE PUBLICATION</code></a>).
    </p></li></ul></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="logical-replication-conflicts.html" title="31.5. Conflicts">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="logical-replication.html" title="Chapter 31. Logical Replication">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="logical-replication-architecture.html" title="31.7. Architecture">Next</a></td></tr><tr><td width="40%" align="left" valign="top">31.5. Conflicts </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.6 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 31.7. Architecture</td></tr></table></div></body></html>