Re: NOT IN query takes forever

Marius Andreiana wrote:

> On Tue, 2004-08-03 at 08:05 -0400, Merlin Moncure wrote:
>
>>>Trying to run this query:
>>>EXPLAIN ANALYSE
>>>select * FROM trans
>>>WHERE query_id NOT IN (select query_id FROM query)
>>>
>>>but it will remain like that forever (cancelled after 30 min).
>>
>>explain analyze actually runs the query to do timings. Just run explain
>>and see what you come up with. More than likely there is a nestloop in
>>there which is causing the long query time.
>>
>>Try bumping up shared buffers some and sort mem as much as you safely
>>can.
>
> Thank you, that did it!
>
> With
> shared_buffers = 3000 # min 16, at least max_connections*2, 8KB each
> sort_mem = 128000 # min 64, size in KB

128 MB for sort_mem is too much, consider that in this way each backend can
use 128 MB for sort operations...
Also shared_buffers = 3000 means 24MB that is not balanced with the 128MB
needed for sort...
Try to bump up 128 MB for shared_buffer ( may be you need to instruct your
OS to allow that ammount of shared memory usage ) and 24MB for sort_mem.

Regards
Gaetano Mendola