| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Andrew Dunstan <andrew(dot)dunstan(at)2ndquadrant(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, "Tsunakawa, Takayuki" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, 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>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, 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: | 2019-03-01 19:34:18 |
| Message-ID: | 30302.1551468858@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Andrew Dunstan <andrew(dot)dunstan(at)2ndquadrant(dot)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
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