hi, I just wait afew days to see whether some one ( with more info about this issue in pg ) reply. but ... so here is my word : >From: InfraRED <[EMAIL PROTECTED]> >To: [EMAIL PROTECTED] >Subject: [GENERAL] when are indexes used? >Date: Sun, 19 Sep 1999 17:29:57 +0200 (CEST) > > >I noticed that indexes are not used sometimes when they could speed up >queries: > >explain select * from auth where uid=30; > Index Scan using auth_uid_key on auth (cost=2.05 rows=1 width=40) > >explain select * from auth where uid<30; > Seq Scan on auth (cost=2.06 rows=11 width=40) > Testing on my machine it works fine. I mean this query uses the index file on my database. >explain select * from auth order by uid; > Sort (cost=2.06 rows=32 width=40) > -> Seq Scan on auth (cost=2.06 rows=32 width=40) > >are there any ways to speed up queries like these? >the exact usage alg. of indexes is documented somewhere? >when is this going to be fixed? It seems that in pg one may only use row field name at the where clause part of the query. ie : select * from auth where uid= 30 ; but if you want to use the index file,don't use it like this : select * from auth where uid= ( 28 + 2 ) ; also you may not use any function on the clause. ie : select * from auth where sqrt(uid)= 30 ; So you have to make the where clause statement very simple with no complexity. Though, due to my old knowledge about oracle, some databases supports these features a little stronger. I will also be glad to hear about more docs about indexing on pg. regards omid. >>************ ______________________________________________________ Get Your Private, Free Email at http://www.hotmail.com ************
