Horton

RE: speeding up planning with partitions

Imai, Yoshikazu <imai.yoshikazu@jp.fujitsu.com>

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From: "Imai, Yoshikazu" <imai.yoshikazu@jp.fujitsu.com>
To: 'Amit Langote' <Langote_Amit_f8@lab.ntt.co.jp>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>, David Rowley <david.rowley@2ndquadrant.com>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2018-11-15T01:19:39Z
Lists: pgsql-hackers 
Hi Amit,

On Tue, Nov 13, 2018 at 10:29 PM, Amit Langote wrote:
> On 2018/11/12 13:35, Imai, Yoshikazu wrote:
> > adjust_appendrel_attrs_multilevel for leaf1: root -> sub1 -> leaf1
> > adjust_appendrel_attrs_multilevel for leaf2: root -> sub1 -> leaf2
> 
> Ah, I see what you mean.
> 
> The root -> sub1 translation will be repeated for each leaf partition
> if done via adjust_appendrel_attrs_multilevel.  On the other hand, if
> we could do the root to sub1 translation once and pass it to the recursive
> call using sub1 as the parent.
> 
> I've changed the patch use adjust_appendrel_attrs.
> 
> > Since it is difficult to explain my thoughts with words, I will show
> > the performance degration case.
> >
> > Partition tables are below two sets.
> 
> [ ... ]
> 
> > Create a generic plan of updation or deletion.
> >
> > [create a delete generic plan]
> > set plan_cache_mode = 'force_generic_plan'; prepare delete_stmt(int)
> > as delete from rt where b = $1; execute delete_stmt(1);
> 
> [ ... ]
> 
> > How amount of memory is used with above tests is...
> >
> > without v5 patches, Set1: 242MB
> > without v5 patches, Set2: 247MB
> > with v5 patches, Set1: 420MB
> > with v5 patches, Set2: 820MB
> 
> Although I didn't aim to fix planning for the generic plan case where
> no pruning occurs, the above result is not acceptable.  That is, the new
> implementation of inheritance update/delete planning shouldn't consume
> more memory than the previous.  In fact, it should've consumed less,
> because the patch claims that it gets rid of redundant processing per
> partition.
> 
> I understood why update/delete planning consumed more memory with the
> patch.  It was due to a problem with the patch that modifies inheritance
> update/delete planning.  The exact problem was that the query tree would
> be translated (hence copied) *twice* for every partition!  First during
> query planning where the query tree would be translated to figure out
> a targetlist for partitions and then again before calling
> grouping_planner.
> Also, the adjust_appendrel_attrs_multilevel made it worse for
> multi-level partitioning case, because of repeated copying for root to
> intermediate partitioned tables, as Imai-san pointed out.
> 
> I've fixed that making sure that query tree is translated only once and
> saved for later steps to use.  Imai-san, please check the memory
> consumption with the latest patch.

Thanks for fixing!
Now, memory consumption is lower than the previous.

with v7 patches, Set1: 223MB
with v7 patches, Set2: 226MB

Thanks,

--
Yoshikazu Imai

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.