Re: Teaching users how they can get the most out of HOT in Postgres 14

On Mon, May 31, 2021 at 10:30:08AM +0900, Masahiko Sawada wrote:
> On Fri, May 28, 2021 at 9:53 AM Peter Geoghegan <pg@bowt.ie> wrote:
>> Another concern with this approach is what it
>> means for the VACUUM command itself. I haven't added an 'auto'
>> spelling that is accepted by the VACUUM command in this POC version.
>> But do I need to at all? Can that just be implied by not having any
>> INDEX_CLEANUP option?
>
> It seems to me that it's better to have INDEX_CLEANUP option of VACUUM
> command support AUTO for consistency. Do you have any concerns about
> supporting it?

I have read through the patch, and I am surprised to see that this
only makes possible to control the optimization at relation level.
The origin of the complaints is that this index cleanup optimization
has been introduced as a new rule that gets enforced at *system*
level, so I think that we should have an equivalent with a GUC to
control the behavior for the whole system.  With what you are
presenting here, one could only disable the optimization for each
relation, one-by-one.  If this optimization proves to be a problem,
it's just going to be harder to users to go through all the relations
and re-tune autovacuum.  Am I missing something?
--
Michael