Horton

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

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andrew Dunstan <andrew.dunstan@2ndquadrant.com>
Cc: 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: 2019-03-01T19:34:18Z
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.

Andrew Dunstan <andrew.dunstan@2ndquadrant.com> writes:
> On 3/1/19 2:14 PM, Tom Lane wrote:
>> Indeed, but I'm not sure that the use-cases are the same.  In particular,
>> unless somebody has done some rather impossible magic, it would be
>> disastrous to apply DISABLE_INDEX_CLEANUP as a reloption, because then
>> it would be persistent and you'd never get a real vacuum operation and
>> soon your disk would be full.  Permanently applying truncation disabling
>> seems less insane.

> You could allow an explicitly set command option to override the reloption.
> It's important for us to be able to control the vacuum phases more. In
> particular, the index cleanup phase can have significant system impact
> but often doesn't need to be done immediately.

I'm not objecting to having a manual command option to skip index cleanup
(which basically reduces to "do nothing but tuple freezing", right?
maybe it should be named/documented that way).  Applying it as a reloption
seems like a foot-gun, though.

			regards, tom lane