On 18 February 2010 12:18, A. Kretschmer <andreas.kretschmer@xxxxxxxxxxxxxx> wrote: > In response to Thom Brown : >> On 18 February 2010 11:55, AI Rumman <rummandba@xxxxxxxxx> wrote: >> > "Not like" operation does not use index. >> > >> > select * from vtiger_contactscf where lower(cf_1253) not like >> > lower('Former%') >> > >> > I created index on lower(cf_1253). >> > >> > How can I ensure index usage in not like operation? >> > Anyone please help. >> > >> >> How many rows do you have in your table? If there are relatively few, >> it probably guesses it to be cheaper to do a sequential scan and >> calculate lower values on-the-fly rather than bother with the index. > > That's one reason, an other reason, i think, is, that a btree-index can't > search with an 'not like' - operator. > Erm.. yes. Now that you say it, it's obvious. :S Thom -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance