Horton

Re: speeding up planning with partitions

Amit Langote <langote_amit_f8@lab.ntt.co.jp>

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From: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: David Rowley <david.rowley@2ndquadrant.com>, "Imai, Yoshikazu" <imai.yoshikazu@jp.fujitsu.com>, Amit Langote <amitlangote09@gmail.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2019-02-19T00:54:47Z
Lists: pgsql-hackers 
Thanks for looking.

On 2019/02/19 2:27, Tom Lane wrote:
> Amit Langote <Langote_Amit_f8@lab.ntt.co.jp> writes:
>> [ v22 patch set ]
> 
> I started to look at this, and immediately choked on the 0001 patch:
> 
>         if (childpruned ||
>             !apply_child_basequals(root, rel, childrel, childRTE, appinfo) ||
>             relation_excluded_by_constraints(root, childrel, childRTE))
>         {
> 
> Frankly, that code is just horrid.  Having a function with side effects
> in an if-test is questionable at the best of times, and having it be
> the second of three conditions (which the third condition silently depends
> on) is unreadable and unmaintainable.
> 
> I think the existing code here is considerably cleaner than what this
> patch proposes.

OK, I think we can just skip this patch.

> I suppose you are doing this because you intend to jam some additional
> cleanup code into the successfully-pruned-it code path, but if said
> code is really too bulky to have multiple copies of, couldn't you
> put it into a subroutine?

Actually, one of the later patches (lazy creation of partition RTEs)
*replaces* the the above code block by:

if (IS_DUMMY_REL(childrel))
    continue;

because with that patch, the step that prunes/excludes children will occur
earlier than set_rel_size / set_append_rel_size.  For pruned children,
there won't RTE/RelOptInfo/AppendRelInfo to begin with.  Children that
survive partition pruning but get excluded due to contradictory quals
(apply_child_basequals returning false) or constraint exclusion will be
marked dummy before even getting to set_append_rel_size.

I'll adjust the patches accordingly.

Thanks,
Amit

Commits

  1. Clean up handling of constraint_exclusion and enable_partition_pruning.

  2. Add test case exercising formerly-unreached code in inheritance_planner.

  3. Speed up planning when partitions can be pruned at plan time.

  4. Avoid crash in partitionwise join planning under GEQO.

  5. Avoid passing query tlist around separately from root->processed_tlist.

  6. Build "other rels" of appendrel baserels in a separate step.

  7. Get rid of duplicate child RTE for a partitioned table.

  8. Rearrange make_partitionedrel_pruneinfo to avoid work when we can't prune.

  9. Don't copy PartitionBoundInfo in set_relation_partition_info.

  10. Move building of child base quals out into a new function

  11. Reorganize planner code moved in b60c39759908

  12. Move inheritance expansion code into its own file

  13. Fix inherited UPDATE/DELETE with UNION ALL subqueries.

  14. Rearrange planner to save the whole PlannerInfo (subroot) for a subquery.