Horton

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

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Pavan Deolasee <pavan.deolasee@gmail.com>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>, Robert Haas <robertmhaas@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, Claudio Freire <klaussfreire@gmail.com>, Greg Stark <stark@mit.edu>, Simon Riggs <simon@2ndquadrant.com>, Jim Nasby <Jim.Nasby@bluetreble.com>, PostgreSQL-Dev <pgsql-hackers@postgresql.org>
Date: 2016-09-14T17:57:42Z
Lists: pgsql-hackers 
Pavan Deolasee <pavan.deolasee@gmail.com> writes:
> On Wed, Sep 14, 2016 at 10:53 PM, Alvaro Herrera <alvherre@2ndquadrant.com>
> wrote:
>> One thing not quite clear to me is how do we create the bitmap
>> representation starting from the array representation in midflight
>> without using twice as much memory transiently.  Are we going to write
>> the array to a temp file, free the array memory, then fill the bitmap by
>> reading the array from disk?

> We could do that.

People who are vacuuming because they are out of disk space will be very
very unhappy with that solution.

			regards, tom lane

Commits

  1. Prefetch blocks during lazy vacuum's truncation scan

  2. Explain unaccounted for space in pgstattuple.