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<?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>31.4. Column Lists</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-row-filter.html" title="31.3. Row Filters" /><link rel="next" href="logical-replication-conflicts.html" title="31.5. Conflicts" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">31.4. Column Lists</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="logical-replication-row-filter.html" title="31.3. Row Filters">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 15.7 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="logical-replication-conflicts.html" title="31.5. Conflicts">Next</a></td></tr></table><hr /></div><div class="sect1" id="LOGICAL-REPLICATION-COL-LISTS"><div class="titlepage"><div><div><h2 class="title" style="clear: both">31.4. Column Lists</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="logical-replication-col-lists.html#LOGICAL-REPLICATION-COL-LIST-EXAMPLES">31.4.1. Examples</a></span></dt></dl></div><p>
Each publication can optionally specify which columns of each table are
replicated to subscribers. The table on the subscriber side must have at
least all the columns that are published. If no column list is specified,
then all columns on the publisher are replicated.
See <a class="xref" href="sql-createpublication.html" title="CREATE PUBLICATION"><span class="refentrytitle">CREATE PUBLICATION</span></a> for details on the syntax.
</p><p>
The choice of columns can be based on behavioral or performance reasons.
However, do not rely on this feature for security: a malicious subscriber
is able to obtain data from columns that are not specifically
published. If security is a consideration, protections can be applied
at the publisher side.
</p><p>
If no column list is specified, any columns added later are automatically
replicated. This means that having a column list which names all columns
is not the same as having no column list at all.
</p><p>
A column list can contain only simple column references. The order
of columns in the list is not preserved.
</p><p>
Specifying a column list when the publication also publishes
<code class="literal">FOR TABLES IN SCHEMA</code> is not supported.
</p><p>
For partitioned tables, the publication parameter
<code class="literal">publish_via_partition_root</code> determines which column list
is used. If <code class="literal">publish_via_partition_root</code> is
<code class="literal">true</code>, the root partitioned table's column list is used.
Otherwise, if <code class="literal">publish_via_partition_root</code> is
<code class="literal">false</code> (the default), each partition's column list is used.
</p><p>
If a publication publishes <code class="command">UPDATE</code> or
<code class="command">DELETE</code> operations, any column list must include the
table's replica identity columns (see
<a class="xref" href="sql-altertable.html#SQL-ALTERTABLE-REPLICA-IDENTITY"><code class="literal">REPLICA IDENTITY</code></a>).
If a publication publishes only <code class="command">INSERT</code> operations, then
the column list may omit replica identity columns.
</p><p>
Column lists have no effect for the <code class="literal">TRUNCATE</code> command.
</p><p>
During initial data synchronization, only the published columns are
copied. However, if the subscriber is from a release prior to 15, then
all the columns in the table are copied during initial data synchronization,
ignoring any column lists.
</p><div class="warning" id="LOGICAL-REPLICATION-COL-LIST-COMBINING"><h3 class="title">Warning: Combining Column Lists from Multiple Publications</h3><p>
There's currently no support for subscriptions comprising several
publications where the same table has been published with different
column lists. <a class="xref" href="sql-createsubscription.html" title="CREATE SUBSCRIPTION"><span class="refentrytitle">CREATE SUBSCRIPTION</span></a> disallows
creating such subscriptions, but it is still possible to get into
that situation by adding or altering column lists on the publication
side after a subscription has been created.
</p><p>
This means changing the column lists of tables on publications that are
already subscribed could lead to errors being thrown on the subscriber
side.
</p><p>
If a subscription is affected by this problem, the only way to resume
replication is to adjust one of the column lists on the publication
side so that they all match; and then either recreate the subscription,
or use <code class="literal">ALTER SUBSCRIPTION ... DROP PUBLICATION</code> to
remove one of the offending publications and add it again.
</p></div><div class="sect2" id="LOGICAL-REPLICATION-COL-LIST-EXAMPLES"><div class="titlepage"><div><div><h3 class="title">31.4.1. Examples</h3></div></div></div><p>
Create a table <code class="literal">t1</code> to be used in the following example.
</p><pre class="programlisting">
test_pub=# CREATE TABLE t1(id int, a text, b text, c text, d text, e text, PRIMARY KEY(id));
CREATE TABLE
</pre><p>
Create a publication <code class="literal">p1</code>. A column list is defined for
table <code class="literal">t1</code> to reduce the number of columns that will be
replicated. Notice that the order of column names in the column list does
not matter.
</p><pre class="programlisting">
test_pub=# CREATE PUBLICATION p1 FOR TABLE t1 (id, b, a, d);
CREATE PUBLICATION
</pre><p>
<code class="literal">psql</code> can be used to show the column lists (if defined)
for each publication.
</p><pre class="programlisting">
test_pub=# \dRp+
Publication p1
Owner | All tables | Inserts | Updates | Deletes | Truncates | Via root
----------+------------+---------+---------+---------+-----------+----------
postgres | f | t | t | t | t | f
Tables:
"public.t1" (id, a, b, d)
</pre><p>
<code class="literal">psql</code> can be used to show the column lists (if defined)
for each table.
</p><pre class="programlisting">
test_pub=# \d t1
Table "public.t1"
Column | Type | Collation | Nullable | Default
--------+---------+-----------+----------+---------
id | integer | | not null |
a | text | | |
b | text | | |
c | text | | |
d | text | | |
e | text | | |
Indexes:
"t1_pkey" PRIMARY KEY, btree (id)
Publications:
"p1" (id, a, b, d)
</pre><p>
On the subscriber node, create a table <code class="literal">t1</code> which now
only needs a subset of the columns that were on the publisher table
<code class="literal">t1</code>, and also create the subscription
<code class="literal">s1</code> that subscribes to the publication
<code class="literal">p1</code>.
</p><pre class="programlisting">
test_sub=# CREATE TABLE t1(id int, b text, a text, d text, PRIMARY KEY(id));
CREATE TABLE
test_sub=# CREATE SUBSCRIPTION s1
test_sub-# CONNECTION 'host=localhost dbname=test_pub application_name=s1'
test_sub-# PUBLICATION p1;
CREATE SUBSCRIPTION
</pre><p>
On the publisher node, insert some rows to table <code class="literal">t1</code>.
</p><pre class="programlisting">
test_pub=# INSERT INTO t1 VALUES(1, 'a-1', 'b-1', 'c-1', 'd-1', 'e-1');
INSERT 0 1
test_pub=# INSERT INTO t1 VALUES(2, 'a-2', 'b-2', 'c-2', 'd-2', 'e-2');
INSERT 0 1
test_pub=# INSERT INTO t1 VALUES(3, 'a-3', 'b-3', 'c-3', 'd-3', 'e-3');
INSERT 0 1
test_pub=# SELECT * FROM t1 ORDER BY id;
id | a | b | c | d | e
----+-----+-----+-----+-----+-----
1 | a-1 | b-1 | c-1 | d-1 | e-1
2 | a-2 | b-2 | c-2 | d-2 | e-2
3 | a-3 | b-3 | c-3 | d-3 | e-3
(3 rows)
</pre><p>
Only data from the column list of publication <code class="literal">p1</code> is
replicated.
</p><pre class="programlisting">
test_sub=# SELECT * FROM t1 ORDER BY id;
id | b | a | d
----+-----+-----+-----
1 | b-1 | a-1 | d-1
2 | b-2 | a-2 | d-2
3 | b-3 | a-3 | d-3
(3 rows)
</pre></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="logical-replication-row-filter.html" title="31.3. Row Filters">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-conflicts.html" title="31.5. Conflicts">Next</a></td></tr><tr><td width="40%" align="left" valign="top">31.3. Row Filters </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.7 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 31.5. Conflicts</td></tr></table></div></body></html>
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