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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>
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
right:
right. This has two forms:
<programlisting>
ALTER TABLE measurement DETACH PARTITION measurement_y2006m02;
ALTER TABLE measurement DETACH PARTITION measurement_y2006m02 CONCURRENTLY;
</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
the data using <command>COPY</command>, <application>pg_dump</application>, or
similar tools. It might also be a useful time to aggregate data
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>
@ -4163,17 +4170,6 @@ ALTER INDEX measurement_city_id_logdate_key
might be poor.)
</para>
</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>
</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>
</varlistentry>
<varlistentry>
<varlistentry id="sql-altertable-detach-partition">
<term><literal>DETACH PARTITION <replaceable class="parameter">partition_name</replaceable> [ CONCURRENTLY | FINALIZE ]</literal></term>
<listitem>