Richard Huxton wrote:
> Mark Lonsdale wrote:
>>
>> Hi Josh
>>
>> Thanks for the feedback, that is most usefull. When you said one of the
>> settings was likely killing us, was it all of the settings for
>> max_fsm_relations, max_fsm_pages, and sort_mem or just the setting for
>> sort_mem ?
>>
>> Can you explain why the setting would be killing me :-)
>
> The sort_mem is crucial. It's memory *per sort*, which means one query
> can use several times that amount.
Worse then that it is:
((sort memory) * (number of sorts)) * (number of connections) = amount
of ram possible to use.
Now... take the following query:
SELECT * FROM foo
JOIN bar on (bar.id = foo.id)
JOIN baz on (baz.id = foo_baz.id)
ORDER BY baz.name, foo.salary;
Over 5 million rows... How much ram you think you just used?
>
>> The long and short is you need to upgrade to at least 7.4, preferrably
>> 8.1.
>
> Joshua means this too. Upgrade to 7.3.16 within the next few days, then
> test out something more recent. You should see some useful performance
> gains from 8.1.
Right. The reason I suggested 7.4 is that he gets VACUUM VERBOSE in a
reasonable fashion but of course 8.1 is better.
Sincerely,
Joshua D. Drake
>
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