Horton

Re: [HACKERS] Partition-wise aggregation/grouping

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Jeevan Chalke <jeevan.chalke@enterprisedb.com>
Cc: Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>, Dilip Kumar <dilipbalaut@gmail.com>, David Rowley <david.rowley@2ndquadrant.com>, Rajkumar Raghuwanshi <rajkumar.raghuwanshi@enterprisedb.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2018-03-08T14:19:18Z
Lists: pgsql-hackers 
On Thu, Mar 8, 2018 at 9:15 AM, Jeevan Chalke
<jeevan.chalke@enterprisedb.com> wrote:
> I am not sure why we don't set reltarget into the grouped_rel too.
>
> But if we do so like we did in partially_grouped_rel, then it will be lot
> easier for partitionwise aggregate as then we don't have to pass target to
> functions creating paths like create_append_path. We now need to update
> generate_gather_paths() to take target too as it is now being called on
> grouped_rel in which reltarget is not set.
>
> But yes, if there is any specific reason we can't do so, then I think the
> same like Ashutosh Said. I didn't aware of such reason though.

I see no problem with setting reltarget for the grouped_rel.  Before
we added partially_grouped_rel, that rel computed paths with two
different targets: partial paths had the partial grouping target, and
non-partial paths had the ordinary grouping target.  But that's fixed
now.

-- 
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.