Re: VACUUM ANALYZE downgrades performance

On Thursday 02 Dec 2004 9:37 pm, 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?

Why not? If the updates are frequent enough, that is *the* solution.

But you could always use autovacuum daemon in most case.

HTH

 Shridhar