On Fri, Mar 10, 2006 at 09:14:27AM +0000, Clive Page wrote: > I have a table cov3 of about 3 million rows, with a B-tree index on an > integer column called hpix. If I do a simple select on this column it > works in milliseconds, using the index naturally: > > select * from cov3 where hpixint = 482787587; ^^^^^^^ That's not the column you said you were using and that your other example uses. Have you verified that hpix has an index?
> So I would like to use this function to find rows, and I try for example: > > select * from cov3 where hpix = healpix(2.85,-11.48); > > but it takes ages. An EXPLAIN shows why, it insists upon a sequential > scan: If healpix() always returns the same output for given input then define it to be IMMUTABLE. For more information see "Function Volatility Categories" in the documentation. http://www.postgresql.org/docs/8.1/interactive/xfunc-volatility.html -- Michael Fuhr ---------------------------(end of broadcast)--------------------------- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly