Horton

Re: generic plans and "initial" pruning

Amit Langote <amitlangote09@gmail.com>

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From: Amit Langote <amitlangote09@gmail.com>
To: Tomas Vondra <tomas@vondra.me>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Tender Wang <tndrwang@gmail.com>, Alexander Lakhin <exclusion@gmail.com>, Robert Haas <robertmhaas@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: 2025-05-23T02:17:48Z
Lists: pgsql-hackers 
On Thu, May 22, 2025 at 10:04 PM Tomas Vondra <tomas@vondra.me> wrote:
> On 5/22/25 10:12, Amit Langote wrote:
> > Note that I’ve only reverted the changes related to deferring locks on
> > prunable partitions. I’m planning to leave the preparatory commits
> > leading up to that one in place unless anyone objects. For reference,
> > here they are in chronological order (the last 3 are bug fixes):
> >
> > bb3ec16e14d Move PartitionPruneInfo out of plan nodes into PlannedStmt
> > d47cbf474ec Perform runtime initial pruning outside ExecInitNode()
> > cbc127917e0 Track unpruned relids to avoid processing pruned relations
> > 75dfde13639 Fix an oversight in cbc127917 to handle MERGE correctly
> > cbb9086c9ef Fix bug in cbc127917 to handle nested Append correctly
> > 28317de723b Ensure first ModifyTable rel initialized if all are pruned
> >
> > I think separating initial pruning from plan node initialization is
> > still worthwhile on its own, as evidenced by the improvements in
> > cbc127917e.
> >
>
> I'm OK with that in principle, assuming the benefits outweigh the risk
> of making backpatching harder. The patches don't seem exceptionally
> large / invasive, but I don't know how often we modify these parts.

Thanks. I agree it's something to be mindful of, but I don’t expect
the reimplementation of the locking deferral to require changes to
this part of the code again. So barring any surprises, it shouldn't be
the case that the pruning code ends up looking significantly different
in v19.

Also, the actual pruning logic hasn’t changed much -- just where it’s
called from.

Let me know if any of that still raises concerns.

-- 
Thanks, Amit Langote

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.