Re: possible wrong query plan on pg 8.3.5,

Цитат от Robert Haas <robertmhaas(at)gmail(dot)com>:

> 2009/9/14 <tv(at)fuzzy(dot)cz>:
>> It seems there's something very wrong - the plans are "equal" but in the
>> first case the results (actual time) are multiplied by 100. Eithere there
>> is some sort of cache (so the second execution is much faster), or the
>> system was busy during the first execution, or there is something wrong
>> with the hardware.
>
> I think you should run this query more than twice. If it's slow the
> first time and fast every time for many executions after that, then
> it's probably just the data getting loaded into the OS cache (or
> shared buffers). If it's bouncing back and forth between fast and
> slow, you might want to check whether your machine is swapping.

I did it many times. Alter the first atempt it works fast, but after a
couple of minutes ( I think after changing the data in cache) the
query is working also very slow.

I do not see any swap on OS.

>
> It might also be helpful to post all the uncommented settings from
> your postgresql.conf file.

postgresql.conf :

max_connections = 2000
shared_buffers = 1800MB
temp_buffers = 80MB
work_mem = 120MB
maintenance_work_mem = 100MB
max_fsm_pages = 404800
max_fsm_relations = 5000

max_files_per_process = 2000
wal_buffers = 64MB
checkpoint_segments = 30
effective_cache_size = 5000MB
default_statistics_target = 800

All the rest are default parameters.

Ivan.

>
> ...Robert
>
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