Re: Where does vacuum FULL write temp-files?

2015-04-15 10:46 GMT+02:00 Andreas Joseph Krogh <andreas(at)visena(dot)com>:

> På onsdag 15. april 2015 kl. 04:34:31, skrev Venkata Balaji N <
> nag1010(at)gmail(dot)com>:
>
>
>
>> I'm planning to vacuum FULL a pg_largeobject relation (after vacuumlo'ing
>> it). The relation is 300GB large so I'm concerned the operation will write
>> full my pg_xlog directory which is on a 200GB (net) RAID1 SSD.
>>
>> Where does vacuum FULL rewrite to, does it use pg_xlog or some other
>> directory?
>>
>
> Which version of PostgreSQL is this ?
>
> If i got your question correctly, VACUUM FULL would rewrite the data to a
> new data file associated with that particular relation (Table) in the
> "$PGDATA/base" directory. This needs an extra disk space at the OS level
> (this is not related to pg_xlog directory).
>
> As VACUUMING is a data change operation, "pg_xlog" will also have only the
> WAL data (modifications) written at the time of VACUUMING.
>
> http://www.postgresql.org/docs/9.4/static/sql-vacuum.html
>
>
> This is PG-9.3
>
> So I understand that VACUUM FULL writes the new table to the same
> tablespace as the original table (also for system-catalogs like
> pg_largeobject), and doesn't use any temp-space outside the location of
> that tablespace?
>

You're right.

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Guillaume.
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