Re: Postgres 11 release notes

Bruce Momjian <bruce@momjian.us>

From: Bruce Momjian <bruce@momjian.us>

To: Alvaro Herrera <alvherre@2ndquadrant.com>

Cc: Andres Freund <andres@anarazel.de>, Teodor Sigaev <teodor@sigaev.ru>, PostgreSQL-development <pgsql-hackers@postgresql.org>

Date: 2018-05-11T19:11:31Z

Lists: pgsql-hackers

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?

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.

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

+ As you are, so once was I.  As I am, so you will be. +
+                      Ancient Roman grave inscription +

Commits

doc: update PG 11 release notes
- 6eb612fea9d0 12.0 cited
Fix misspelled pg_trgm contrib name in PostgreSQL 11 release notes
- 3abc5a67edfd 12.0 landed
Doc: clarify release note text about v11's new window function features.
- 510421c45fb4 11.0 landed
- 11a3aeeb5e17 12.0 landed
Improve wording of release notes item
- bee6a683a5c3 11.0 landed
Fix typos in release notes
- fb6accd27b99 11.0 landed
Doc: preliminary list of PG11 major features.
- 4aad161c9a6d 11.0 landed
Make numeric power() handle NaNs according to the modern POSIX spec.
- d1fc750b5199 11.0 landed
Various improvements of skipping index scan during vacuum technics
- 8e12f4a250d2 11.0 cited
Revert back-branch changes in power()'s behavior for NaN inputs.
- f74d83b3034f 10.4 cited
Avoid wrong results for power() with NaN input on more platforms.
- 6bdf1303b34b 11.0 cited
Avoid wrong results for power() with NaN input on some platforms.
- 61b200e2f582 11.0 cited
Skip full index scan during cleanup of B-tree indexes when possible
- 857f9c36cda5 11.0 cited
Rewrite the code that applies scan/join targets to paths.
- 11cf92f6e2e1 11.0 cited
Postpone generate_gather_paths for topmost scan/join rel.
- 3f90ec8597c3 11.0 cited
Add casts from jsonb
- c0cbe00fee6d 11.0 cited
Make plpgsql use its DTYPE_REC code paths for composite-type variables.
- 4b93f57999a2 11.0 cited
Don't allow VACUUM VERBOSE ANALYZE VERBOSE.
- 921059bd66c7 11.0 cited
Pass InitPlan values to workers via Gather (Merge).
- e89a71fb449a 11.0 cited
Account for the effect of lossy pages when costing bitmap scans.
- 5edc63bda68a 11.0 cited
Allow no-op GiST support functions to be omitted.
- d3a4f89d8a3e 11.0 cited
Rearm statement_timeout after each executed query.
- f8e5f156b30e 11.0 cited
Push limit through subqueries to underlying sort, where possible.
- 1f6d515a67ec 11.0 cited