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

Nathan Bossart <bossartn@amazon.com>

From: "Bossart, Nathan" <bossartn@amazon.com>

To: Andres Freund <andres@anarazel.de>

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: 2019-03-04T21:40:53Z

Lists: pgsql-hackers

Commits

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Add TRUNCATE parameter to VACUUM.
- b84dbc8eb80b 12.0 landed
Add vacuum_truncate reloption.
- 119dcfad988d 12.0 landed
Allow VACUUM to be run with index cleanup disabled.
- a96c41feec6b 12.0 cited

On 3/4/19, 12:11 PM, "Andres Freund" <andres@anarazel.de> wrote:
> 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.

Wouldn't it be better to adjust the cost and threshold parameters or
to manually vacuum during quieter periods?  I suppose setting
DISABLE_INDEX_CLEANUP on a relation during busy periods could be
useful if you really need to continue reclaiming transaction IDs, but
that seems like an easy way to accidentally never vacuum indexes.

Nathan