2011/6/5 Håvard Wahl Kongsgård <haavard.kongsga...@gmail.com> > Hi, my database performance badly on substring comparison between two very > large tables. > In postgresql 8.4 is it possible to create a index on a substring, or must > I create an new field for the substring match ( and then create a new index > for that field)? > > -- > Håvard Wahl Kongsgård > > http://havard.security-review.net/ > >
Hi, I've checked that for 9.0, however for 8.4 should work as well: CREATE INDEX i_test_sbstr ON test( substring(t, 5, 3) ); It is important that the substring() parameters in the index definition are the same as you use in your query. regards Szymon
