On Sun, 2005-02-13 at 20:40 -0800, Stephan Szabo wrote: > On Mon, 14 Feb 2005, Neil Dugan wrote: > > > I am using PostgreSQL 7.4.7 > > I have a table with serveral fields two of these are a serialno > > (bigserial) and name(varchar). I have created two indexs on these > > fields. > > 1) on name > > 2) on name,serialno > > if I use the command > > 'select * from table order by name limit 1' > > everything is OK > > if I use the command > > 'select * from table order by name desc limit 1' > > everything is OK > > if I use the command > > 'select * from table order by name,serialno limit 1' > > everything is OK > > if I use the command > > 'select * from table order by name,serialno desc limit 1' > > The command is SLOW and gives back the INCORRECT data. > > Without any example data and result, it's hard to say what you were > expecting or got. I'd expect the highest numbered serialno record for the > lowest sorting name from the above which is what any tests I've tried do. > > Right now I believe it won't consider index usage because the ordering > asked for doesn't match either a forward ordering of the index(name, > serialno) or a reverse order (name desc, serialno desc). Thanks Stephan, for the hint on using desc twice. 'select * from table order by name desc,serialno desc limit 1' does work. I didn't realise it was separating the order into two sections, I'm sorry if this caused any trouble for you. My mistake, bye! ---------------------------(end of broadcast)--------------------------- TIP 1: subscribe and unsubscribe commands go to majordomo@xxxxxxxxxxxxxx
