Horton

Re: generic plans and "initial" pruning

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Amit Langote <amitlangote09@gmail.com>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Andres Freund <andres@anarazel.de>, Daniel Gustafsson <daniel@yesql.se>, David Rowley <dgrowleyml@gmail.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>, Thom Brown <thom@linux.com>
Date: 2024-08-19T17:52:07Z
Lists: pgsql-hackers 
Robert Haas <robertmhaas@gmail.com> writes:
> But that seems somewhat incidental to what this thread is about.

Perhaps.  But if we're running into issues related to that, it might
be good to set aside the long-term goal for a bit and come up with
a cleaner answer for intra-session locking.  That could allow the
pruning problem to be solved more cleanly in turn, and it'd be
an improvement even if not.

> Do you have a view on what the way forward might be?

I'm fresh out of ideas at the moment, other than having a hope that
divide-and-conquer (ie, solving subproblems first) might pay off.

> This thread has gotten a tad depressing, honestly. All of the opinions
> about what we ought to do seem to be based on the firm conviction that
> X or Y or Z will not work, rather than on the confidence that A or B
> or C will work. Yet I'm inclined to believe this problem is solvable.

Yeah.  We are working in an extremely not-green field here, which
means it's a lot easier to see pre-existing reasons why X will not
work than to have confidence that it will work.  But hey, if this
were easy then we'd have done it already.

			regards, tom lane

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.