Horton

Re: Postgres 11 release notes

Amit Langote <langote_amit_f8@lab.ntt.co.jp>

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From: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>
To: Bruce Momjian <bruce@momjian.us>
Cc: Amit Langote <amitlangote09@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2018-05-23T01:54:17Z
Lists: pgsql-hackers 
On 2018/05/23 10:36, Bruce Momjian wrote:
> On Wed, May 23, 2018 at 10:28:41AM +0900, Amit Langote wrote:
>>> Uh, we already have this in the release notes:
>>>
>>>         Allow faster partition elimination during query processing (Amit
>>>         Langote, David Rowley, Dilip Kumar)
>>>
>>>         This speeds access to partitioned tables with many partitions.
>>>
>>> Do you want me to add the git commit hash to this release note entry?
>>
>> I suppose you meant the above as an entry for performance improvement of
>> partition "pruning".  The commit I quoted is concerned with making "tuple
>> routing" a bit faster, but as David said that's not making it as fast as
>> it could really be.  So, we should hold off from touting it as an
>> improvement at this point and I have to agree.  Sorry for the noise.
> 
> OK, no problem.  So _finding_ the rows is faster, but adding rows to
> partitioned tables with many partitions is still slow, got it.

Yeah.

To be honest, even _finding_ is not yet performing the best it could be,
which I guess David would chime in to say.  We know what needs to be fixed
to get the close-to-ideal performance there, but didn't have time to do it
for PG 11.  To clarify, what changed is that we replaced constraint
exclusion, which has to consider the partition constraint of *all*
partitions individually, as an algorithm for partition pruning by a faster
alternative that only looks at the parent table's partition descriptor.
That gives a good boost but that's not the end of it.  Moreover, addition
of this new pruning algorithm enabled the development of execution time
pruning which is a completely new feature.

Thanks,
Amit

Commits

  1. doc: update PG 11 release notes

  2. Fix misspelled pg_trgm contrib name in PostgreSQL 11 release notes

  3. Doc: clarify release note text about v11's new window function features.

  4. Improve wording of release notes item

  5. Fix typos in release notes

  6. Doc: preliminary list of PG11 major features.

  7. Make numeric power() handle NaNs according to the modern POSIX spec.

  8. Various improvements of skipping index scan during vacuum technics

  9. Revert back-branch changes in power()'s behavior for NaN inputs.

  10. Avoid wrong results for power() with NaN input on more platforms.

  11. Avoid wrong results for power() with NaN input on some platforms.

  12. Skip full index scan during cleanup of B-tree indexes when possible

  13. Rewrite the code that applies scan/join targets to paths.

  14. Postpone generate_gather_paths for topmost scan/join rel.

  15. Add casts from jsonb

  16. Make plpgsql use its DTYPE_REC code paths for composite-type variables.

  17. Don't allow VACUUM VERBOSE ANALYZE VERBOSE.

  18. Pass InitPlan values to workers via Gather (Merge).

  19. Account for the effect of lossy pages when costing bitmap scans.

  20. Allow no-op GiST support functions to be omitted.

  21. Rearm statement_timeout after each executed query.

  22. Push limit through subqueries to underlying sort, where possible.