Horton

Re: Partition-wise aggregation/grouping

Jeevan Chalke <jeevan.chalke@enterprisedb.com>

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From: Jeevan Chalke <jeevan.chalke@enterprisedb.com>
To: legrand legrand <legrand_legrand@hotmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2017-12-08T04:21:17Z
Lists: pgsql-hackers 
On Fri, Dec 8, 2017 at 3:08 AM, legrand legrand <legrand_legrand@hotmail.com
> wrote:

> Hello,
>
> I'm testing Partition wise and found a strange result in V8 patch
> see  init_star_schema_agg.sql
> <http://www.postgresql-archive.org/file/t348768/init_star_schema_agg.sql>
>
> Explain gives
>   ->  Seq Scan on facts_p2  (...) (actual time=0.012..0.012 rows=1 loops=1)
> for partitions that are joined with empty partitions
>
> I was expecting a message saying that partition facts_p2 was not accessed
>
> Am I wrong ?
>

Is this related to partition-wise aggregation as you saying you found this
behaviour on v8 patch?

I have tried your testcase on master and see similar plan.

I had a look over the plan and I did not see any empty relation at the
planning time.


> Regards
> PAscal
>
>
>
> --
> Sent from: http://www.postgresql-archive.org/PostgreSQL-hackers-
> f1928748.html
>
>


-- 
Jeevan Chalke
Technical Architect, Product Development
EnterpriseDB Corporation
The Enterprise PostgreSQL Company

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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.