On 03/03/2011 13:29, obamabarak@xxxxx wrote:
I use pgsql 9.0.3 and I know that postgresql tries to use the fields in indexes instead of the original table if it possible But when I run SELECT COUNT(id) FROM tab or SELECT COUNT(*) FROM tab where there "id" is PRIMARY KEY and there are other indexes there I get execution plan that doesnt use any indexes, but sequentab scanning the original table.
Because when you do SELECT COUNT(*) without any WHERE.... clause, then PostgreSQL has to scan through *all* the rows in the table in order to count them.
Ray. -- Raymond O'Donnell :: Galway :: Ireland rod@xxxxxx -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
