Doc: add information about partition locking

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 <[email protected]>
Discussion: https://postgr.es/m/CAApHDvp738G75HfkKcfXaf3a8s%3D6mmtOLh46tMD0D2hAo1UCzA%40mail.gmail.com
Backpatch-through: 13

diff --git a/doc/src/sgml/ddl.sgml b/doc/src/sgml/ddl.sgml
index 40da56923d9fc38637c5d684930f03fa80233818..5c98f4e2a3dd1a0e7fefbe0e68a5eee55382da8b 100644 (file)
--- a/doc/src/sgml/ddl.sgml
+++ b/doc/src/sgml/ddl.sgml
@@ -4690,7 +4690,9 @@ EXPLAIN SELECT count(*) FROM measurement WHERE logdate >= DATE '2008-01-01';
        It is possible to determine the number of partitions which were
        removed during this phase by observing the
        <quote>Subplans Removed</quote> property in the
-       <command>EXPLAIN</command> output.
+       <command>EXPLAIN</command> output.  It's important to note that any
+       partitions removed by the partition pruning done at this stage are
+       still locked at the beginning of execution.
       </para>
      </listitem>