Re: Query only slow on first run

On Wed, Nov 28, 2007 at 09:16:08PM +0100, cluster wrote:
> Hmm, actually I still don't understand why it takes 6400 ms to fetch the
> rows. As far as I can see the index used is "covering" so that real row
> lookups shouldn't be necessary.

The indexes don't contain visibility information, so Postgres has to look up
the row on disk to verify it isn't dead.

> Also, only the the random_numbers induces by questions with status = 1
> should be considered - and this part is a relatively small subset.

Again, you'll need to have a combined index if you want this to help you any.

/* Steinar */
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