Re: Database size stays constant but disk space keeps shrinking -- postgres 9.1

We had a situation where external sort was creating a humungous temp
file and the space was reclaimed when the process was completed.

Thanks.
Dinesh

On 9/28/2012 8:59 AM, Steve Crawford wrote:
> On 09/27/2012 07:01 PM, Greg Williamson wrote:
>> Steve (and others who replied):
>> ...
>> The other is a slimmed-down version of our production database,
>> which gets
>>> recreated hourly by a shell script which pulls data from remote
>>> servers, does a
>>> pg_dump of the resulting 3 gig database, and then drops it.
>>> ...
>
> Could you explain this process in more detail? Are you creating a new
> database, reading in data, dumping then dropping the whole database or
> just manipulating tables within an existing database?
>
>>> Have you checked to see if there are any processes that have open
>>> handles to
>>> deleted files (lsof -X | grep deleted). Deleted files won't show up
>>> in du
>>> but won't release their disk space until the process exits. Perhaps
>>> a script
>>> or scripts, even one of your hourly ones, that terminate when the
>>> server
>>> restarts? You could save the output of lsof and ps immediately
>>> before and after
>>> a restart and compare them.
>> lsof -X | grep deleted | wc -l
>>
>> shows: 835 such files.
>>
>> A couple:
>> postgres 2540 postgres 50u REG 8,3
>> 409600 93429 /var/lib/postgresql/9.1/main/base/2789
>> 200/11816 (deleted)
>> postgres 2540 postgres 51u REG 8,3 18112512
>> 49694570 /var/lib/postgresql/9.1/main/base/2789
>> 200/2791679 (deleted)
>> <...>...
> I'll leave it to you and Tom to puzzle over the the postgres-related
> open files. Meanwhile, I'm a bit curious about the other 800+ and
> whether they are associated with scripts or processes that are
> connected to PostgreSQL.
>
> First, what is the output of "select * from pg_stat_activity;"? Are
> there connections you don't expect to see? If you force any of them
> closed (after checking with anyone who may be impacted), do you see
> any file handles released or disk-space freed?
>
> Second, do any of the processes associated with the other
> open-but-deleted files relate to programs or scripts that connect to
> PostgreSQL? Next time you do a restart, do any of the processes exit
> or do any of the deleted files get closed?
>
> I'm wondering if you have processes that connect to PostgreSQL which
> terminate and release their file-handles when PG is restarted.
>
> Cheers,
> Steve
>
>
>