Odd behavior with temp usage logging

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Odd behavior with temp usage logging

От:
Josh Berkus <josh@agliodbs.com>
Дата:
Folks,

I turned on temp file logging for PostgreSQL to see if I needed to 
adjust work_mem.  Oddly, it's logging file usage up to 33 times per 
executed query (and no, the query isn't large enough to need 33 separate 
sorts).

Any idea what's going on here?

--Josh

Re: Odd behavior with temp usage logging

От:
Craig Ringer <craig@postnewspapers.com.au>
Дата:
Josh Berkus wrote:
> Folks,
> 
> I turned on temp file logging for PostgreSQL to see if I needed to
> adjust work_mem.  Oddly, it's logging file usage up to 33 times per
> executed query (and no, the query isn't large enough to need 33 separate
> sorts).

Are you sure there's not a sort happening inside a loop? It might help
if you posted the actual log messages along with the output of `EXPLAIN
ANALYZE' on your query.

--
Craig Ringer

Re: Odd behavior with temp usage logging

От:
Josh Berkus <josh@agliodbs.com>
Дата:
Craig Ringer wrote:
> Josh Berkus wrote:
>> Folks,
>>
>> I turned on temp file logging for PostgreSQL to see if I needed to
>> adjust work_mem.  Oddly, it's logging file usage up to 33 times per
>> executed query (and no, the query isn't large enough to need 33 separate
>> sorts).
> 
> Are you sure there's not a sort happening inside a loop? It might help
> if you posted the actual log messages along with the output of `EXPLAIN
> ANALYZE' on your query.

Hmmm, it's possible.  The sort sizes seem very large for the query in 
question, though.  Will have to check when I get back on the system.

That would make a TODO in tempfile logging though ... it would be *far* 
more useful to colect summary stats per query than log each individual sort.

--Josh
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