Re: postmaster consuming /lots/ of memory with hash aggregate. why?

2010/11/12 Jon Nelson <jnelson+pgsql(at)jamponi(dot)net>:
> On Thu, Nov 11, 2010 at 10:26 PM, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:
>> Hello
>>
>> look on EXPLAIN ANALYZE command. Probably your statistic are out, and
>> then planner can be confused. EXPLAIN ANALYZE statement show it.
>
> As I noted earlier, I did set statistics to 1000 an re-ran vacuum
> analyze and the plan did not change.

this change can do nothing. this is default in config. did you use
ALTER TABLE ALTER COLUMN SET STATISTIC = ... ? and ANALYZE

>
> What other diagnostics can I provide? This still doesn't answer the
> 40000 row question, though. It seems absurd to me that the planner
> would give up and just use 40000 rows (0.02 percent of the actual
> result).
>

there can be some not well supported operation, then planner use a
some % from rows without statistic based estimation

Pavel
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> Jon
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