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

From: Michael Paquier <michael(at)paquier(dot)xyz>
To: "Tsunakawa, Takayuki" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com>
Cc: 'Julien Rouhaud' <rjuju123(at)gmail(dot)com>, Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>, "Jamison, Kirk" <k(dot)jamison(at)jp(dot)fujitsu(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: reloption to prevent VACUUM from truncating empty pages at the end of relation
Date: 2019-02-22 04:47:52
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On Fri, Feb 22, 2019 at 02:38:56AM +0000, Tsunakawa, Takayuki wrote:
> From: Julien Rouhaud [mailto:rjuju123(at)gmail(dot)com]
>> FWIW, I prefer shrink over truncate, though I'd rather go with
>> vacuum_shink_enabled as suggested previously.
> Thanks. I'd like to leave a committer to choose the name. FWIW, I
> chose shrink_enabled rather than vacuum_shrink_enabled because this
> property may be used in other shrink situations in the future. What
> I imagined was that with the zheap, DELETE or some maintenance
> operation, not vacuum, may try to shrink the table. I meant this
> property to indicate "whether this table shrinks or not" regardless
> of the specific operation that can shrink the table.

I don't think that we want to use a too generic name and it seems more
natural to reflect the context where it is used in the parameter name.
If we were to shrink with a similar option for other contexts, we
would most likely use a different option. Depending on the load
pattern, users should also be able to disable or enable a subset of
contexts as well.

So I agree with Julien that [auto]vacuum_shrink_enabled is more
adapted for this stuff.

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