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

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>
Cc: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: reloption to prevent VACUUM from truncating empty pages at the end of relation
Date: 2018-04-18 19:33:08
Message-ID: 11754.1524079988@sss.pgh.pa.us
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I wrote:
> Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com> writes:
>> What if we remember the buffers as seen by count_nondeletable_pages() and
>> then just discard those specific buffers instead of scanning the entire
>> shared_buffers again?

> That's an idea.

BTW, before pushing too hard on any of this, we need to think about the
data-corruption hazard that MauMau just reminded us about. I'm afraid
what we're likely to end up with after the dust settles is worse
performance than today, not better :-(.

https://postgr.es/m/5BBC590AE8DF4ED1A170E4D48F1B53AC@tunaPC

regards, tom lane

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