Horton

Re: Removing unneeded self joins

Michał Kłeczek <michal@kleczek.org>

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From: Michał Kłeczek <michal@kleczek.org>
To: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2023-03-06T05:30:03Z
Lists: pgsql-hackers

Commits

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  1. Remove GUC_NOT_IN_SAMPLE from enable_self_join_elimination

  2. Put enable_self_join_elimination into postgresql.conf.sample

  3. Get rid of ojrelid local variable in remove_rel_from_query()

  4. Implement Self-Join Elimination

  5. Revert: Remove useless self-joins

  6. Replace lateral references to removed rels in subqueries

  7. Replace relids in lateral subquery parse tree during SJE

  8. Forbid SJE with result relation

  9. Fix misuse of RelOptInfo.unique_for_rels cache by SJE

  10. Replace the relid in some missing fields during SJE

  11. Revert 56-bit relfilenode change and follow-up commits.

  12. Stabilize timetz test across DST transitions.

  13. Speed up finding EquivalenceClasses for a given set of rels

  14. Fix mark-and-restore-skipping test case to not be a self-join.

Hi All,

I just wanted to ask about the status and plans for this patch.
I can see it being stuck at “Waiting for Author” status in several commit tests.

I think this patch would be really beneficial for us as we heavily use views to structure out code.
Each view is responsible for providing some calculated values and they are joined in a query to retrieve the full set of information.

Not sure how the process works and how I could help (I am absolutely not capable of helping with coding I am afraid - but could sponsor a (small :) ) bounty to speed things up).

Thanks,
Michal

> On 16 Dec 2022, at 07:45, Andrey Lepikhov <a.lepikhov@postgrespro.ru> wrote:
> 
> On 12/6/22 23:46, Andres Freund wrote:
>> This doesn't pass the main regression tests due to a plan difference.
>> https://cirrus-ci.com/task/5537518245380096
>> https://api.cirrus-ci.com/v1/artifact/task/5537518245380096/testrun/build/testrun/regress/regress/regression.diffs
>> diff -U3 /tmp/cirrus-ci-build/src/test/regress/expected/join.out /tmp/cirrus-ci-build/build/testrun/regress/regress/results/join.out
>> --- /tmp/cirrus-ci-build/src/test/regress/expected/join.out	2022-12-05 19:11:52.453920838 +0000
>> +++ /tmp/cirrus-ci-build/build/testrun/regress/regress/results/join.out	2022-12-05 19:15:21.864183651 +0000
>> @@ -5806,7 +5806,7 @@
>>   Nested Loop
>>     Join Filter: (sj_t3.id = sj_t1.id)
>>     ->  Nested Loop
>> -         Join Filter: (sj_t3.id = sj_t2.id)
>> +         Join Filter: (sj_t2.id = sj_t3.id)
>>           ->  Nested Loop Semi Join
>>                 ->  Nested Loop
>>                       ->  HashAggregate
> This change in the test behaviour is induced by the a5fc4641
> "Avoid making commutatively-duplicate clauses in EquivalenceClasses."
> Nothing special, as I see. Attached patch fixes this.
> 
> -- 
> Regards
> Andrey Lepikhov
> Postgres Professional
> <v39-0001-Remove-self-joins.patch>