Re: Where does vacuum FULL write temp-files?

På onsdag 15. april 2015 kl. 04:34:31, skrev Venkata Balaji N <nag1010(at)gmail(dot)com
<mailto: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
<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?   Thanks.   --
Andreas Joseph Krogh CTO / Partner - Visena AS Mobile: +47 909 56 963
andreas(at)visena(dot)com <mailto:andreas(at)visena(dot)com> www.visena.com
<https://www.visena.com> <https://www.visena.com>