Horton

Re: Partition-wise aggregation/grouping

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Antonin Houska <ah@cybertec.at>
Cc: Jeevan Chalke <jeevan.chalke@enterprisedb.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2017-04-26T16:57:00Z
Lists: pgsql-hackers 
On Wed, Apr 26, 2017 at 6:28 AM, Antonin Houska <ah@cybertec.at> wrote:
> Attached is a diff that contains both patches merged. This is just to prove my
> assumption, details to be elaborated later. The scripts attached produce the
> following plan in my environment:
>
>                    QUERY PLAN
> ------------------------------------------------
>  Parallel Finalize HashAggregate
>    Group Key: b_1.j
>    ->  Append
>          ->  Parallel Partial HashAggregate
>                Group Key: b_1.j
>                ->  Hash Join
>                      Hash Cond: (b_1.j = c_1.k)
>                      ->  Seq Scan on b_1
>                      ->  Hash
>                            ->  Seq Scan on c_1
>          ->  Parallel Partial HashAggregate
>                Group Key: b_2.j
>                ->  Hash Join
>                      Hash Cond: (b_2.j = c_2.k)
>                      ->  Seq Scan on b_2
>                      ->  Hash
>                            ->  Seq Scan on c_2

Well, I'm confused.  I see that there's a relationship between what
Antonin is trying to do and what Jeevan is trying to do, but I can't
figure out whether one is a subset of the other, whether they're both
orthogonal, or something else.  This plan looks similar to what I
would expect Jeevan's patch to produce, except i have no idea what
"Parallel" would mean in a plan that contains no Gather node.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

Commits

  1. postgres_fdw: Push down partition-wise aggregation.

  2. Remove 'target' from GroupPathExtraData.

  3. Implement partition-wise grouping/aggregation.

  4. Don't pass the grouping target around unnecessarily.

  5. Determine grouping strategies in create_grouping_paths.

  6. Defer creation of partially-grouped relation until it's needed.

  7. Split create_grouping_paths into degenerate and non-degenerate cases.

  8. Pass additional arguments to a couple of grouping-related functions.

  9. Fix logic error in add_paths_to_partial_grouping_rel.

  10. Minor cleanup of code related to partially_grouped_rel.

  11. Add a new upper planner relation for partially-aggregated results.

  12. Charge cpu_tuple_cost * 0.5 for Append and MergeAppend nodes.

  13. Rename enable_partition_wise_join to enable_partitionwise_join

  14. Factor some code out of create_grouping_paths.

  15. Pad XLogReaderState's main_data buffer more aggressively.

  16. Prevent int128 from requiring more than MAXALIGN alignment.

  17. Fix DROP SUBSCRIPTION hang

  18. Inject $(ICU_LIBS) regardless of platform.

  19. Some preliminary refactoring towards partitionwise join.