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Improve documentation on DETACH PARTITION lock levels 

This was forgotten in 71f4c8c6f7.

Reported-by: Pavel Luzanov <p.luzanov@postgrespro.ru>
Author: Amit Langote <amitlangote09@gmail.com>
Discussion: https://postgr.es/m/0688e7c3-8bc8-a3e4-9d8e-3bcbbf3e1f4d@postgrespro.ru
This commit is contained in:
Alvaro Herrera 2021-05-06 16:42:30 -04:00
parent c9787385db
commit db6e1aeb95
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2 changed files with 11 additions and 15 deletions
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24
doc/src/sgml/ddl.sgml
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@ -3915,18 +3915,25 @@ DROP TABLE measurement_y2006m02;
<para> <para>
Another option that is often preferable is to remove the partition from Another option that is often preferable is to remove the partition from
the partitioned table but retain access to it as a table in its own the partitioned table but retain access to it as a table in its own
right: right. This has two forms:
<programlisting> <programlisting>
ALTER TABLE measurement DETACH PARTITION measurement_y2006m02; ALTER TABLE measurement DETACH PARTITION measurement_y2006m02;
ALTER TABLE measurement DETACH PARTITION measurement_y2006m02 CONCURRENTLY;
</programlisting> </programlisting>
This allows further operations to be performed on the data before These allow further operations to be performed on the data before
it is dropped. For example, this is often a useful time to back up it is dropped. For example, this is often a useful time to back up
the data using <command>COPY</command>, <application>pg_dump</application>, or the data using <command>COPY</command>, <application>pg_dump</application>, or
similar tools. It might also be a useful time to aggregate data similar tools. It might also be a useful time to aggregate data
into smaller formats, perform other data manipulations, or run into smaller formats, perform other data manipulations, or run
reports. reports. The first form of the command requires an
<literal>ACCESS EXCLUSIVE</literal> lock on the parent table.
Adding the <literal>CONCURRENTLY</literal> qualifier as in the second
form allows the detach operation to require only
<literal>SHARE UPDATE EXCLUSIVE</literal> lock on the parent table, but see
<link linkend="sql-altertable-detach-partition"><literal>ALTER TABLE ... DETACH PARTITION</literal></link>
for details on the restrictions.
</para> </para>
<para> <para>
@ -4163,17 +4170,6 @@ ALTER INDEX measurement_city_id_logdate_key
might be poor.) might be poor.)
</para> </para>
</listitem> </listitem>
<listitem>
<para>
Some operations require a stronger lock when using declarative
partitioning than when using table inheritance. For example,
removing a partition from a partitioned table requires taking
an <literal>ACCESS EXCLUSIVE</literal> lock on the parent table,
whereas a <literal>SHARE UPDATE EXCLUSIVE</literal> lock is enough
in the case of regular inheritance.
</para>
</listitem>
</itemizedlist> </itemizedlist>
</para> </para>

2
doc/src/sgml/ref/alter_table.sgml
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@ -967,7 +967,7 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
</listitem> </listitem>
</varlistentry> </varlistentry>
<varlistentry> <varlistentry id="sql-altertable-detach-partition">
<term><literal>DETACH PARTITION <replaceable class="parameter">partition_name</replaceable> [ CONCURRENTLY | FINALIZE ]</literal></term> <term><literal>DETACH PARTITION <replaceable class="parameter">partition_name</replaceable> [ CONCURRENTLY | FINALIZE ]</literal></term>
<listitem> <listitem>