Alvaro Herrera <[email protected]> writes:
> Herouth Maoz wrote:
>> We found out that the table's response depends on the rate of ANALYZE being
>> performed. We have tuned the values in pg_autovacuum so that we have around
>> one analyze per minute.
>>
>> What is bothering me is that sometimes the auto vacuum daemon decides to
>> perform a vacuum analyze rather than just analyze. If it just does a vacuum
>> independent of the analyze, we don't see much impact on performance. But if
>> it does vacuum analyze, it means that until vacuum is over, it doesn't do
>> another analyze, and this may take about five minutes, in which our
>> performance under load conditions might deteriorate.
> Hmm, this is an use case we never thought about. I don't think there's
> any way to coerce autovacuum into doing what you want it to do. I
> suggest you turn analyze off for this table (say by setting a very large
> scale factor), and analyze it manually through cron or something.
Hmm. Given the churn rate on the table, I'm having a very hard time
believing that you don't need to vacuum it pretty dang often. Maybe the
direction you need to be moving is to persuade autovac to vacuum it
*more* often, not less often, so that the time needed to finish each
vacuum is small enough.
regards, tom lane
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