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Doc: add information about partition locking

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The documentation around locking of partitions for the executor startup
phase of run-time partition pruning wasn't clear about which partitions
were being locked.  Fix that.

Reviewed-by: Tender Wang <tndrwang@gmail.com>
Discussion: https://postgr.es/m/CAApHDvp738G75HfkKcfXaf3a8s%3D6mmtOLh46tMD0D2hAo1UCzA%40mail.gmail.com
Backpatch-through: 13
This commit is contained in:
David Rowley 2025-04-02 14:02:44 +13:00
parent b3219c69fc
commit 121d774cae
1 changed files with 7 additions and 1 deletions
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doc/src/sgml/ddl.sgml
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@ -5075,7 +5075,13 @@ EXPLAIN SELECT count(*) FROM measurement WHERE logdate &gt;= DATE '2008-01-01';
It is possible to determine the number of partitions which were It is possible to determine the number of partitions which were
removed during this phase by observing the removed during this phase by observing the
<quote>Subplans Removed</quote> property in the <quote>Subplans Removed</quote> property in the
<command>EXPLAIN</command> output. <command>EXPLAIN</command> output. The query planner obtains locks for
all partitions which are part of the plan. However, when the executor
uses a cached plan, locks are only obtained on the partitions which
remain after partition pruning done during the initialization phase of
execution, i.e., the ones shown in the <command>EXPLAIN</command>
output and not the ones referred to by the
<quote>Subplans Removed</quote> property.
</para> </para>
</listitem> </listitem>