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: 'David Rowley' <david.rowley@2ndquadrant.com>, Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>
Cc: Amit Langote <amitlangote09@gmail.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2019-01-11T06:10:00Z
Lists: pgsql-hackers 
Hi David,

On Thu, Jan 10, 2019 at 4:02 PM, David Rowley wrote:
> 3. I wonder if there's a better way to handle what
> build_dummy_partition_rel() does. I see the child's relid to the
> parent's relid and makes up a fake AppendRelInfo and puts it in the
> parent's slot.  What's going to happen when the parent is not the
> top-level parent? It'll already have a AppendRelInfo set.
... 
> 
> select * from parent p1 inner join parent p2 on p1.a=p2.a where p1.id < 10;

I think there is a mistake in the select SQL.
"p1.id < 10" doesn't prune any partition because tables are partitioned by
column "a" in your definition. Isn't it?

> Does that not mean that the if (parent->top_parent_relids) will always
> be false in build_dummy_partition_rel() and it'll only ever get
> rtekind == RTE_RELATION?

At least, I checked if (parent->top_parent_relids) can be true if I execute
below SQL.

select * from parent p1 inner join parent p2 on p1.a=p2.a where p1.id < 15;

I couldn't check other points you mentioned, but I also think
build_dummy_partition_rel() needs more consideration because I felt it has
complicated logic when I was checking around here.


Amit,
I also realized there are some mistakes in the comments around this function.

+ * build_dummy_partition_rel
+ *		Build a RelOptInfo and AppendRelInfo for a pruned partition 
s/and AppendRelInfo/and an AppendRelInfo/

+	 * Now we'll need a (no-op) AppendRelInfo for parent, because we're
+	 * setting the dummy partition's relid to be same as the parent's.
s/a \(no-op\) AppendRelInfo/an \(no-op\) AppendRelInfo/

--
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.