Horton

Re: Vacuum: allow usage of more than 1GB of work mem

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Simon Riggs <simon@2ndquadrant.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Claudio Freire <klaussfreire@gmail.com>, Jim Nasby <Jim.Nasby@bluetreble.com>, PostgreSQL-Dev <pgsql-hackers@postgresql.org>
Date: 2016-09-06T18:23:48Z
Lists: pgsql-hackers 
On Tue, Sep 6, 2016 at 2:16 PM, Simon Riggs <simon@2ndquadrant.com> wrote:
> What occurs to me is that we can exactly predict how many tuples we
> are going to get when we autovacuum, since we measure that and we know
> what the number is when we trigger it.
>
> So there doesn't need to be any guessing going on at all, nor do we
> need it to be flexible.

No, that's not really true.  A lot can change between the time it's
triggered and the time it happens, or even while it's happening.
Somebody can run a gigantic bulk delete just after we start the
VACUUM.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

Commits

  1. Prefetch blocks during lazy vacuum's truncation scan

  2. Explain unaccounted for space in pgstattuple.