On 07/05/2012 04:00 PM, Albe Laurenz wrote:
> 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.
Actually, that's a thought. Autovaccum can't see uncomitted work, and
thus can't analyze it. Maybe they need an explicit ANALYZE or two after
a bulk insert or update during their data load.
--
Craig Ringer