Re: Why does a simple query not use an obvious index?

On Sun, Aug 29, 2004 at 06:03:43PM -0400, Tom Lane wrote:
> The expression "now() - something" is not a constant, so the planner
> is faced with "timestampfield > unknownvalue".  Its default assumption
> about the number of rows that will match is much too high to make an
> indexscan look profitable (from memory, I think it guesses that about
> a third of the table will match...).

Out of curiosity, does the subselect query I presented earlier in the thread
count as "a constant"? It gives the correct query plan, but this could of
course just be correct by accident...

/* Steinar */
--
Homepage: http://www.sesse.net/