Re: VACUUM ANALYZE downgrades performance

On Thu, 2004-12-02 at 17:07 +0100, Dmitry Karasik wrote:
> Hi Thomas!
>
> Thomas> Look at the ACTUAL TIME. It dropped from 0.029ms (using the index
> Thomas> scan) to 0.009ms (using a sequential scan.)
>
> Thomas> Index scans are not always faster, and the planner/optimizer knows
> Thomas> this. VACUUM ANALYZE is best run when a large proportion of data
> Thomas> has been updated/loaded or in the off hours to refresh the
> Thomas> statistics on large datasets.
>
> While I agree that generally this is true, look how stupid this
> behavior looks in this particular case: A developer creates a table
> and index, knowing that the table will be large and will be intensively
> used. An admin runs 'VACUUM ANALYZE' when table is occasionally empty,
> and next, say, 1 day, until another 'VACUUM ANALYZE' starts, the index
> is simply not used! Sure you don't suppose to run 'VACUUM ANALYZE' every
> 5 minutes as a solution, right?

You might want to try this on the next 8.0 beta to come out, or against
CVS. Tom recently applied some changes which should mitigate this
situation.

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