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@peoplecall.com> wrote:
>> On Tue, Aug 23, 2016 at 2:32 PM, Ilya Kazakevich
>> <Ilya.Kazakevich@jetbrains.com> 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
willbe 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
adrian.klaver@aklaver.com
