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| author | David Rowley <drowley@postgresql.org> | 2025-04-02 14:02:44 +1300 |
|---|---|---|
| committer | David Rowley <drowley@postgresql.org> | 2025-04-02 14:02:44 +1300 |
| commit | 121d774caea4c93c8b36fb20a17ef774e60894d6 (patch) | |
| tree | 8011896adf18e567e4b7a3bccf01be29e3a46dec /doc/src | |
| parent | b3219c69fc1e161df8d380c464b3f2cce3b6cab9 (diff) | |
| download | postgresql-121d774caea4c93c8b36fb20a17ef774e60894d6.tar.gz postgresql-121d774caea4c93c8b36fb20a17ef774e60894d6.zip | |
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 <tndrwang@gmail.com>
Discussion: https://postgr.es/m/CAApHDvp738G75HfkKcfXaf3a8s%3D6mmtOLh46tMD0D2hAo1UCzA%40mail.gmail.com
Backpatch-through: 13
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/ddl.sgml | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/doc/src/sgml/ddl.sgml b/doc/src/sgml/ddl.sgml index cdb1a07e9d3..d2082b7e88e 100644 --- a/doc/src/sgml/ddl.sgml +++ b/doc/src/sgml/ddl.sgml @@ -5075,7 +5075,13 @@ 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. 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> |