Horton

Re: reloption to prevent VACUUM from truncating empty pages at the end of relation

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Robert Haas <robertmhaas@gmail.com>, Michael Paquier <michael@paquier.xyz>, Julien Rouhaud <rjuju123@gmail.com>, "Tsunakawa, Takayuki" <tsunakawa.takay@jp.fujitsu.com>, Laurenz Albe <laurenz.albe@cybertec.at>, "Jamison, Kirk" <k.jamison@jp.fujitsu.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, Amit Kapila <amit.kapila16@gmail.com>, Fujii Masao <masao.fujii@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2019-03-01T19:21:24Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Add TRUNCATE parameter to VACUUM.

  2. Add vacuum_truncate reloption.

  3. Allow VACUUM to be run with index cleanup disabled.

Hi,

On 2019-03-01 14:17:33 -0500, Tom Lane wrote:
> Andres Freund <andres@anarazel.de> writes:
> > OTOH, as the main reason for wanting to disable truncation is that a
> > user is getting very undesirable HS conflicts, it doesn't seem right to
> > force them to change the reloption on all tables, and then somehow force
> > it to be set on all tables created at a later stage. I'm not sure how
> > that'd be better?
> 
> I think we should reject the whole patch, tbh, and go do something
> about the underlying problem instead.  Once we've made truncation
> not require AEL, this will be nothing but a legacy wart that we'll
> have a hard time getting rid of.

IDK, it's really painful in the field, and I'm not quite seeing us
getting rid of the AEL for v12. I think it's a wart, but one that works
around a pretty important usability issue. And I think we should just
remove the GUC without any sort of deprecation afterwards, if necessary
we can add a note to the docs to that effect.  It's not like preventing
truncation from happening is a very intrusive / dangerous thing to do.

Greetings,

Andres Freund