Greg Stark wrote: > > Tom Lane <[EMAIL PROTECTED]> writes: > > > In any case, this discussion is predicated on the assumption that the > > operations involving the bitmap are a significant fraction of the total > > time, which I think is quite uncertain. Until we build it and profile > > it, we won't know that. > > The other thought I had was that it would be difficult to tell when to follow > this path. Since the main case where it wins is when the individual indexes > aren't very selective but the combination is very selective, and we don't have > inter-column correlation statistics ...
We actually have heap access cost and index access cost. You could compare costs of looking at all of index A's heap vs. looking at index B and then hopefully fewer heap rows. -- Bruce Momjian | http://candle.pha.pa.us [EMAIL PROTECTED] | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 ---------------------------(end of broadcast)--------------------------- TIP 2: you can get off all lists at once with the unregister command (send "unregister YourEmailAddressHere" to [EMAIL PROTECTED])
