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: "Bossart, Nathan" <bossartn@amazon.com>
Cc: Masahiko Sawada <sawada.mshk@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Andrew Dunstan <andrew.dunstan@2ndquadrant.com>, Robert Haas <robertmhaas@gmail.com>, "Tsunakawa, Takayuki" <tsunakawa.takay@jp.fujitsu.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, Michael Paquier <michael@paquier.xyz>, Julien Rouhaud <rjuju123@gmail.com>, Laurenz Albe <laurenz.albe@cybertec.at>, "Jamison, Kirk" <k.jamison@jp.fujitsu.com>, Amit Kapila <amit.kapila16@gmail.com>, Fujii Masao <masao.fujii@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2019-03-04T20:11:12Z
Lists: pgsql-hackers

Commits

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  1. Add TRUNCATE parameter to VACUUM.

  2. Add vacuum_truncate reloption.

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

Hi,

On 2019-03-04 20:03:37 +0000, Bossart, Nathan wrote:
> On 3/3/19, 9:23 PM, "Masahiko Sawada" <sawada.mshk@gmail.com> wrote:
> > FWIW, I agree that we have options for vacuum as vacuum
> > command options. But for reloptions, I think if the persistence the
> > setting could be problematic we should not. According to the
> > discussions so far, I think VACUUM_SHRINK_ENABLED is the one option
> > that can be available as both vacuum command option and reloptions.
> > But I'm not sure there is good use case even if we can set
> > DISABLE_INDEX_CLEANUP as reloptions.
> 
> +1
> 
> The DISABLE_INDEX_CLEANUP option is intended to help avoid transaction
> ID wraparound and should not be used as a long-term VACUUM strategy
> for a table.

I'm not quite convinced this is right.  There's plenty sites that
practically can't use autovacuum because it might decide to vacuum the
5TB index because of 300 dead tuples in the middle of busy periods.  And
without an reloption that's not controllable.

- Andres