Horton

Re: generic plans and "initial" pruning

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Amit Langote <amitlangote09@gmail.com>
Cc: Simon Riggs <simon.riggs@enterprisedb.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2022-01-18T14:53:05Z
Lists: pgsql-hackers 
On Tue, Jan 18, 2022 at 3:10 AM Amit Langote <amitlangote09@gmail.com> wrote:
> Pursuing that kind of a project would perhaps have been more
> worthwhile if the locking issue had affected more than just this
> particular case, that is, the case of running prepared statements over
> partitioned tables using generic plans.  Addressing this by
> rearchitecting run-time pruning (and plancache to some degree) seemed
> like it might lead to this getting fixed in a bounded timeframe.  I
> admit that the concerns that Robert has raised about the patch make me
> want to reconsider that position, though maybe it's too soon to
> conclude.

I wasn't trying to say that your approach was dead in the water. It
does create a situation that can't happen today, and such things are
scary and need careful thought. But redesigning the locking mechanism
would need careful thought, too ... maybe even more of it than sorting
this out.

I do also agree with Simon that this is an important problem to which
we need to find some solution.

-- 
Robert Haas
EDB: http://www.enterprisedb.com

Commits

  1. Stamp 19beta1.

  2. Revert "Don't lock partitions pruned by initial pruning"

  3. Ensure first ModifyTable rel initialized if all are pruned

  4. Fix bug in cbc127917 to handle nested Append correctly

  5. Remove unstable test suite added by 525392d57

  6. Don't lock partitions pruned by initial pruning

  7. Fix an oversight in cbc127917 to handle MERGE correctly

  8. Track unpruned relids to avoid processing pruned relations

  9. Perform runtime initial pruning outside ExecInitNode()

  10. Move PartitionPruneInfo out of plan nodes into PlannedStmt

  11. Fix setrefs.c's failure to do expression processing on prune steps.

  12. Remove obsolete executor cleanup code

  13. Revert "Move PartitionPruneInfo out of plan nodes into PlannedStmt"

  14. Move PartitioPruneInfo out of plan nodes into PlannedStmt

  15. Refactor and cleanup runtime partition prune code a little

  16. Remove some unnecessary fields from Plan trees.

  17. Remove more redundant relation locking during executor startup.

  18. Shut down Gather's children before shutting down Gather itself.