Horton

Re: speeding up planning with partitions

Justin Pryzby <pryzby@telsasoft.com>

View thread View on postgr.es
From: Justin Pryzby <pryzby@telsasoft.com>
To: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>
Cc: "Imai, Yoshikazu" <imai.yoshikazu@jp.fujitsu.com>, David Rowley <david.rowley@2ndquadrant.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, pgsql-hackers@postgresql.org
Date: 2019-01-03T15:39:00Z
Lists: pgsql-hackers 
Hi,

I don't think I can't help with code review, but I loaded our largest
customer's schema into pg12dev and tested with this patch.  It's working well -
thanks for your work.

Details follow.

We have tooo many tables+indices so this vastly improves planning speed.  Our
large customers have ~300 parent tables and total ~20k child tables with total
~80k indices.  Our largest tables heirarchies have ~1200 child tables, which
may have as many as 6-8 indices each.  And 5-10 of the largest heirarchies are
unioned together in a view.

Running pg11.1, explaining query for the largest view with condition eliminates
all but today's tables can take several minutes with a cold cache, due to not
only stat()ing every file in every table in a partition heirarchy, before
pruning, but also actually open()ing all their indices.

Running 11dev with your v10 patch applied, this takes 2244ms with empty buffer
cache after postmaster restarted on a totally untuned instance (and a new
backend, with no cached opened files).

I was curious why it took even 2sec, and why it did so many opens() (but not
20k of them that PG11 does):

[pryzbyj@database postgresql]$ cut -d'(' -f1 /tmp/strace-12dev-explain |sort |uniq -c |sort -nr
   2544 lseek
   1263 open
   ...

It turns out 1050 open()s are due to historic data which is no longer being
loaded and therefor never converted to relkind=p (but hasn't exceeded the
retention interval so not yet DROPped, either).

Cheers,
Justin

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.