On Fri, 3 Oct 2003, Kathy Zhu wrote: > Hi, > > I notices a weird thing here. > > version 7.2.1 > on Solaris > > table "test", has a field "state". > There are 4 "state" values, 1, 2, 3, 4. > > select count(*) from test group by state; > took 11500 msec > > but > > select count(*) from test where state = 1; > select count(*) from test where state = 2; > select count(*) from test where state = 3; > select count(*) from test where state = 4; > total took 626 msec > > Why ??
First thought was caching: the disk blocks are cached in memory after the first qery so all the others just fetch from there. Second thought: well I haven't really had it but indexes and sorting is sort of sloshing around in my mind. Not sure how that applies to here since I can't remember if the first would require the sort step having retrieved all the tuples and the others would just use the index pages. It is Friday though. -- Nigel J. Andrews ---------------------------(end of broadcast)--------------------------- TIP 8: explain analyze is your friend
