Horton

Re: Postgres 11 release notes

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Bruce Momjian <bruce@momjian.us>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>, Teodor Sigaev <teodor@sigaev.ru>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2018-05-11T19:22:08Z
Lists: pgsql-hackers 
On 2018-05-11 15:11:31 -0400, Bruce Momjian wrote:
> On Fri, May 11, 2018 at 04:00:58PM -0300, Alvaro Herrera wrote:
> > Bruce Momjian wrote:
> > 
> > > OK, so what is the text that people will understand?  This?
> > > 
> > > 	Prevent manual VACUUMs on append-only tables from performing
> > > 	needless index scans
> > 
> > Make vacuum cheaper by avoiding scans of btree indexes when not
> > necessary
> > ?
> > 
> > Why "manual vacuum"?  It's a problem with vacuums invoked from
> > autovacuum too.
> 
> Uh, from the commit it says:
> 
> 	When workload on particular table is append-only, then autovacuum
> 	isn't intended to touch this table. However, user may run vacuum
> 	manually in order to fill visibility map and get benefits of
> 	--------
> 	index-only scans.  Then ambulkdelete wouldn't be called for
> 	indexes of such table (because no heap tuples were deleted), only
> 	                               ---------------------------
> 	amvacuumcleanup would be called In this case, amvacuumcleanup
> 	would perform full index scan for two objectives: put recyclable
> 	pages into free space map and update index statistics.
> 
> Why would autovacuum run on a table with no expired index entries?

Anti-Wraparound is one case. One where it's really painful to take
forever on lots of unchanged tables. Lots of hot updates another.

Btw, is it just me, or do the commit and docs confuse say stalled when
stale is intended?


> Personally, I think the fact that autovacuum doesn't run on suvch tables
> and therefore doesn't automatically do index-only scans is a problem. I
> tried to fix it years ago, but failed and gave up.

I'm really unhappy about that too.

Greetings,

Andres Freund

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.