index cdb1a07e9d3bf6ef0167cb4a9fbac99081c2f4c7..d2082b7e88ec78747dd5fedf09ab010b9e4d289f 100644 (file)
@@ -5075,7 +5075,13 @@ EXPLAIN SELECT count(*) FROM measurement WHERE logdate >= DATE '2008年01月01日';
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. 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>
</listitem>