On 08/23/2016 07:06 AM, Rakesh Kumar wrote:
Is it true that one datafile in PG can only belong to one object (table/index)
Yes, assuming by datafile you mean an on disk file. Though one object
may have many in disk files associated with it:
https://www.postgresql.org/docs/9.5/static/storage-file-layout.html
Details start just under Table 63-1. Contents of PGDATA
On Tue, Aug 23, 2016 at 9:55 AM, Francisco Olarte
<folarte@xxxxxxxxxxxxxx> wrote:
On Tue, Aug 23, 2016 at 2:32 PM, Ilya Kazakevich
<Ilya.Kazakevich@xxxxxxxxxxxxx> wrote:
does that mean that I should always execute a VACUUM to recover the
wasted space when an error is triggered or will the auto-vacuum mechanism
do the job by itself ?
If you have autovacuum enabled it will clean up tablespace. However, space will not be returned to filesystem but will be reused by database.
You may run VACUUM FULL manually to return it to filesystem.
A normal vacuum may also return some space, specially after a big bulk
load, see second paragraph of 23.1.2 the URL you posted:
https://www.postgresql.org/docs/9.1/static/routine-vacuuming.html
Where it says "However, it will not return the space to the operating
system, except in the special case where one or more pages at the end
of a table become entirely free and an exclusive table lock can be
easily obtained.". A big aborted bulk load may just fit the case, as
it may put a lot of tuples at new pages at the end and be executed in
a low-load period where the lock is easier to acquire.
Francisco Olarte.
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Adrian Klaver
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