Re: vacuum full doubled database size

On 13/03/2020 15:15, Ron wrote:
> This is why I'd VACUUM FULL in a planned manner, one or two tables at a
> time, and *locally* from crontab.

That's not really viable on any remotely busy system: VACUUM FULL claims
exclusive table locks, causing queries to hang
(https://www.postgresql.org/docs/current/sql-vacuum.html#NOTES mentions
this too).

Tools like pg_repack can do some live shrinking.

I've also had some success at reclaiming space without large scale locks
by carefully crafting some atomic DELETE + INSERT in order to force
tuples from the tail end into gaps at lower CTIDs (physical page
address) that were made available by previous plain VACUUMs - regular
VACUUM will clip data files if all the tuples beyond a given offset are
dead.

>
> On 3/13/20 8:41 AM, Zwettler Markus (OIZ) wrote:
>>
>> We did a "vacuum full" on a database which had been interrupted by a
>> network outage.
>>
>> We found the database size doubled afterwards.
>>
>> Autovacuum also found a lot of orphaned tables afterwards.
>>
>> The ophan temp objects went away after a cluster restart while the db
>> size remained doubled.
>>
>> Any idea?
>>
>> Postgres 9.6.17
>>
>
> --
> Angular momentum makes the world go 'round.

--
Regards

Fabio Ugo Venchiarutti
OSPCFC Network Engineering Dpt.
Ocado Technology

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