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: Rajkumar Raghuwanshi <rajkumar.raghuwanshi@enterprisedb.com>
Cc: Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>, Robert Haas <robertmhaas@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, David Rowley <david.rowley@2ndquadrant.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2017-11-28T08:50:40Z
Lists: pgsql-hackers 
On Tue, Nov 28, 2017 at 12:37 PM, Rajkumar Raghuwanshi <
rajkumar.raghuwanshi@enterprisedb.com> wrote:

> On Thu, Nov 23, 2017 at 6:38 PM, Jeevan Chalke
> <jeevan.chalke@enterprisedb.com> wrote:
> > Let me know if I missed any comment to be fixed.
>
> Hi,
>
> I have applied v8 patches on commit id 8735978e7aebfbc499843630131c18
> d1f7346c79,
> and getting below observation, please take a look.
>
> Observation:
> "when joining a foreign partition table with local partition table
> getting wrong output
> with partition_wise_join enabled, same is working fine on PG-head
> without aggregates patch."
>

I have observed the same behavior on the master branch too when
partition-wise join path is selected irrespective of this patch-set.

This is happening because data on the foreign table is not compliance with
the partitioning constraints.


> Test-case:
> CREATE EXTENSION postgres_fdw;
> CREATE SERVER pwj_server FOREIGN DATA WRAPPER postgres_fdw OPTIONS
> (dbname 'postgres',port '5432',use_remote_estimate 'true');
> CREATE USER MAPPING FOR PUBLIC SERVER pwj_server;
>
> CREATE TABLE fplt1 (a int,  c text) PARTITION BY LIST(c);
> CREATE TABLE fplt1_p1 (a int,  c text);
> CREATE TABLE fplt1_p2 (a int,  c text);
> CREATE FOREIGN TABLE ftplt1_p1 PARTITION OF fplt1 FOR VALUES IN
> ('0000', '0001', '0002', '0003') SERVER pwj_server OPTIONS (TABLE_NAME
> 'fplt1_p1');
> CREATE FOREIGN TABLE ftplt1_p2 PARTITION OF fplt1 FOR VALUES IN
> ('0004', '0005', '0006', '0007') SERVER pwj_server OPTIONS (TABLE_NAME
> 'fplt1_p2');
> INSERT INTO fplt1_p1 SELECT i, to_char(i%8, 'FM0000') FROM
> generate_series(0, 199, 2) i;
> INSERT INTO fplt1_p2 SELECT i, to_char(i%8, 'FM0000') FROM
> generate_series(200, 398, 2) i;
>
> CREATE TABLE lplt2 (a int,  c text) PARTITION BY LIST(c);
> CREATE TABLE lplt2_p1 PARTITION OF lplt2 FOR VALUES IN ('0000',
> '0001', '0002', '0003');
> CREATE TABLE lplt2_p2 PARTITION OF lplt2 FOR VALUES IN ('0004',
> '0005', '0006', '0007');
> INSERT INTO lplt2 SELECT i, to_char(i%8, 'FM0000') FROM
> generate_series(0, 398, 3) i;
>
> SELECT t1.c, t2.c,count(*) FROM fplt1 t1 JOIN lplt2 t2 ON (t1.c = t2.c
> and t1.a = t2.a)  WHERE t1.a % 25 = 0 GROUP BY 1,2 ORDER BY t1.c,
> t2.c;
>   c   |  c   | count
> ------+------+-------
>  0000 | 0000 |     1
>  0004 | 0004 |     1
>  0006 | 0006 |     1
> (3 rows)
>
> SET enable_partition_wise_join = on;
> SELECT t1.c, t2.c,count(*) FROM fplt1 t1 JOIN lplt2 t2 ON (t1.c = t2.c
> and t1.a = t2.a)  WHERE t1.a % 25 = 0 GROUP BY 1,2 ORDER BY t1.c,
> t2.c;
>   c   |  c   | count
> ------+------+-------
>  0000 | 0000 |     1
>  0004 | 0004 |     1
> (2 rows)
>
>
> Thanks & Regards,
> Rajkumar Raghuwanshi
> QMG, EnterpriseDB Corporation
>



-- 
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.