| From: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com> |
| Cc: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Claudio Freire <klaussfreire(at)gmail(dot)com>, Greg Stark <stark(at)mit(dot)edu>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, PostgreSQL-Dev <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Vacuum: allow usage of more than 1GB of work mem |
| Date: | 2016-09-15 15:50:28 |
| Message-ID: | fa6627ae-268c-85b0-e33b-3c909a4a8636@2ndquadrant.com |
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| Lists: | pgsql-hackers |
On 09/14/2016 07:57 PM, Tom Lane wrote:
> Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com> writes:
>> On Wed, Sep 14, 2016 at 10:53 PM, Alvaro Herrera <alvherre(at)2ndquadrant(dot)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.
The people are usually running out of space for data, while these files
would be temporary files placed wherever temp_tablespaces points to. I'd
argue if this is a source of problems, the people are already in deep
trouble due to sorts, CREATE INDEX, ... as those commands may also
generate a lot of temporary files.
regards
Tomas
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