Horton

Re: ALTER SYSTEM between upgrades

Daniel Gustafsson <daniel@yesql.se>

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From: Daniel Gustafsson <daniel@yesql.se>
To: Bruce Momjian <bruce@momjian.us>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>, PostgreSQL-documentation <pgsql-docs@postgresql.org>
Date: 2020-07-14T10:52:23Z
Lists: pgsql-hackers, pgsql-docs 
> On 14 Jul 2020, at 01:58, Bruce Momjian <bruce@momjian.us> wrote:

> I am creating a new thread to discuss the question raised by Alvaro of
> how many ALTER SYSTEM settings are lost during major upgrades.  Do we
> properly document that users should migrate their postgresql.conf _and_
> postgresql.auto.conf files during major upgrades?  I personally never
> thought of this until now.

Transferring postgresql.conf is discussed to some degree in the documentation
for pg_upgrade:

    11. Restore pg_hba.conf
	If you modified pg_hba.conf, restore its original settings.  It might
	also be necessary to adjust other configuration files in the new
	cluster to match the old cluster, e.g.  postgresql.conf.

.. as well as upgrading via pg_dumpall:

    4.  Restore your previous pg_hba.conf and any postgresql.conf
    modifications.

One can argue whether those bulletpoints are sufficient for stressing the
importance, but it's at least mentioned.  There is however no mention of
postgresql.auto.conf which clearly isn't helping anyone, so we should fix that.

Taking that a step further, maybe we should mention additional config files
which could be included via include directives?  There are tools out there who
avoid changing the users postgresql.conf by injecting an include directive
instead; they might've placed the included file alongside postgresql.conf.

cheers ./daniel

Commits

  1. Add hash_mem_multiplier GUC.

  2. HashAgg: use better cardinality estimate for recursive spilling.

  3. Remove hashagg_avoid_disk_plan GUC.

  4. Doc fixup for hashagg_avoid_disk_plan GUC.

  5. Rework HashAgg GUCs.

  6. Disk-based Hash Aggregation.

  7. Implement partition-wise grouping/aggregation.

  8. Defer creation of partially-grouped relation until it's needed.