Re: Delay in completion of aggregation inserts when run in a single commit - PG 9.1.2

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От Albe Laurenz
Тема Re: Delay in completion of aggregation inserts when run in a single commit - PG 9.1.2
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Msg-id D960CB61B694CF459DCFB4B0128514C2081BEC77@exadv11.host.magwien.gv.at
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Ответ на Delay in completion of aggregation inserts when run in a single commit - PG 9.1.2  (Akash Kodibail <akash.kodibail@onmobile.com>)
Ответы Re: Delay in completion of aggregation inserts when run in a single commit - PG 9.1.2  (Craig Ringer <ringerc@ringerc.id.au>)
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Akash Kodibail wrote:
> Problem:
[...]
>
> -  Aggregation process almost never completes which is a set of 15
insert queries. Entire
> process happens in a single commit (population of staging tables and
aggregation).
>
> -  When I run these 15 queries individually, it happens in no time.
>
> Could you be kind enough to explain how differently queries run when
in a "single commit" as opposed
> to running each of them individually?

Apart from minor differences (current_timestamp, ...) the
main difference is that there is no COMMIT after each query.
COMMIT is expensive since it requires a write to hard disk.

Try to get the execution plans of the queries in both cases
and see if you can spot a difference.
The auto_explain contrib module might come handy for that.

Yours,
Laurenz Albe

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