| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Yura Sokolov <y(dot)sokolov(at)postgrespro(dot)ru>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [PoC] Improve dead tuple storage for lazy vacuum |
| Date: | 2021-07-30 19:13:49 |
| Message-ID: | CA+Tgmoakg4A4m2O0f_oa6DUiDmFGS9kJWNrNjj-JY5LGqdAv-Q@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Jul 29, 2021 at 3:14 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
> I think those advantages are far outstripped by the big disadvantage of
> needing to either size the array accurately from the start, or to
> reallocate the whole array. Our current pre-allocation behaviour is
> very wasteful for most vacuums but doesn't handle large work_mem at all,
> causing unnecessary index scans.
I agree that the current pre-allocation behavior is bad, but I don't
really see that as an issue with my idea. Fixing that would require
allocating the array in chunks, but that doesn't really affect the
core of the idea much, at least as I see it.
But I accept that Yura has a very good point about the memory usage of
what I was proposing.
--
Robert Haas
EDB: http://www.enterprisedb.com
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