On Mon, Jan 12, 2009 at 12:23 PM, Andreas Kretschmer <akretschmer@xxxxxxxxxxxxx> wrote: > Jörg Kiegeland <kiegeland@xxxxxx> schrieb: > >> Hello, >> >> I created a multicolumn index on the columns c_1,..,c_n . >> If I do use only a true subset of these columns in a SQL query, is the >> index still efficient? >> Or is it better to create another multicolumn index defined on this subset? > > Create several indexes for each column, since 8.1 PG can use a so called > Bitmap Index Scan. Read more about that: I've found that when you do frequently query on two or more columns, a multi-column index is faster than bitmap scans, especially for larger data sets. -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
