Horton

Re: speeding up planning with partitions

Floris Van Nee <florisvannee@optiver.com>

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From: Floris Van Nee <florisvannee@Optiver.com>
To: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>, David Rowley <david.rowley@2ndquadrant.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Imai Yoshikazu <yoshikazu_i443@live.jp>, "jesper.pedersen@redhat.com" <jesper.pedersen@redhat.com>, "Imai, Yoshikazu" <imai.yoshikazu@jp.fujitsu.com>, Amit Langote <amitlangote09@gmail.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, Robert Haas <robertmhaas@gmail.com>, Justin Pryzby <pryzby@telsasoft.com>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2019-04-05T09:13:29Z
Lists: pgsql-hackers 
Thanks for the details! Indeed the versions with now()/current_date use the runtime pruning rather than planning time. I wasn't aware of the use of 'today' though - that could be useful in case we're sure statements won't be prepared.

Previously (v10/ partly v11) it was necessary to make sure that statements on partioned tables were never prepared, because run-time pruning wasn't available - using a generic plan was almost always a bad option. Now in v12 it seems to be a tradeoff between whether or not run-time pruning can occur. If pruning is possible at planning time it's probably still better not to prepare statements, whereas if run-time pruning has to occur, it's better to prepare them.

One unrelated thing I noticed (but I'm not sure if it's worth a separate email thread) is that the changed default of jit=on in v12 doesn't work very well with a large number of partitions at run-time, for which a large number get excluded at run-time. A query that has an estimated cost above jit_optimize_above_cost takes about 30 seconds to run (for a table with 1000 partitions), because JIT is optimizing the full plan. Without JIT it's barely 20ms (+400ms planning). I can give more details in a separate thread if it's deemed interesting.

Planning Time: 411.321 ms
JIT:
  Functions: 5005
  Options: Inlining false, Optimization true, Expressions true, Deforming true
  Timing: Generation 721.472 ms, Inlining 0.000 ms, Optimization 16312.195 ms, Emission 12533.611 ms, Total 29567.278 ms

-Floris

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.