I've found what to me is a surprising locking behavior when querying partitioned data as described in section 5.10 of the User's Manual.
I have an empty parent table with a number of child tables containing data. Each child has a CHECK condition on the relevant column. I am executing a SELECT query against the parent table with a condition on the column in the CHECK in the WHERE clause.
I have constraint_exclusion set to partition.
If I run EXPLAIN on the query, I get a result that shows that only the child tables whose CHECKs are consistent with the WHERE clause are searched. This is exactly what I expected.
However, when I run the query, AccessShareLocks are obtained by the transaction for all child tables (and their indices).
Am I misunderstanding something? I seems that these locks shouldn't exist if the query plan doesn't use most of the child tables.
If this is a bug, perhaps it could be fixed in a future release. I would be beneficial to my application, as we most often are only writing to one partition in any given day. If a query against older data is running, the write transaction could still proceed.
-Ed
Ed Behn / Staff Engineer / Airline and Network Services
Information Management Services
2551 Riva Road, Annapolis, MD 21401 USA
Phone: 410-266-4426 / Cell: 240-696-7443
