Horton

Re: [HACKERS] Partition-wise aggregation/grouping

Jeevan Chalke <jeevan.chalke@enterprisedb.com>

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From: Jeevan Chalke <jeevan.chalke@enterprisedb.com>
To: Robert Haas <robertmhaas@gmail.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: 2018-02-27T09:29:18Z
Lists: pgsql-hackers

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Hi Robert,


On Mon, Feb 26, 2018 at 8:03 PM, Robert Haas <robertmhaas@gmail.com> wrote:

>
> Committed after incorporating your other fixes and updating the
> optimizer README.
>

Thanks Robert.

Off-list Rajkumar has reported an issue. When we have enable_hashagg set to
false, and Gather Merge path is chosen, it ended-up in an error saying
"ERROR:  Aggref found in non-Agg plan node".

I had a look over his provided testcase and observed that when we create a
Gather Merge path over a cheapest partial path by sorting it explicitly as
generate_gather_paths won't consider it, we accidentally used cheapest
partial path from the input_rel to create a Gather Merge; instead we need a
cheapest partial path from the partially_grouped_rel.

Attached fix_aggref_in_non-agg_error.patch fixing this.
test_for_aggref_in_non-agg_error.patch has a testcase reported by Rajkumar
which I have added in a aggregates.sql.

While doing so, I have observed few cleanup changes, added those in
misc_cleanup.patch.

---

While re-basing my partitionwise aggregate changes, I observed that when we
want to create partial aggregation paths for a child partition, we don't
need to add Gather or Gather Merge on top of it as we first want to append
them all and then want to stick a gather on it. So it will be better to
have that code part in a separate function so that we can call it from
required places.

I have attached patch (create_non_partial_paths.patch) for it including all
above fix.

Thanks


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



-- 
Jeevan Chalke
Technical Architect, Product Development
EnterpriseDB Corporation
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.