is there any way to explicitly force the postgres to use index scan On Thu, Mar 6, 2008 at 12:06 PM, A. Kretschmer < [EMAIL PROTECTED]> wrote:
> am Thu, dem 06.03.2008, um 1:26:46 -0500 mailte Mark Mielke folgendes: > > > > > > There aren't a general solution. If you realy need the exact > count of > > tuples than you can play with a TRIGGER and increase/decrease > the > > tuple-count for this table in an extra table. > > > > > > Of course, this means accepting the cost of obtaining update locks on > the count > > table. > > > > The original poster should understand that they can either get a fast > estimated > > count, or they can get a slow accurate count (either slow in terms of > select > > using count(*) or slow in terms of updates using triggers and locking). > > > > Other systems have their own issues. An index scan may be faster than a > table > > scan for databases that can accurately determine counts using only the > index, > > No. The current index-implementation contains no information about the > row-visibility within the current transaction. You need to scan the > whole data-table to obtain if the current row are visible within the > current transaction. > > > > but it's still a relatively slow operation, and people don't normally > need an > > accurate count for records in the range of 100,000+? :-) > > right. > > > Andreas > -- > Andreas Kretschmer > Kontakt: Heynitz: 035242/47150, D1: 0160/7141639 (mehr: -> Header) > GnuPG-ID: 0x3FFF606C, privat 0x7F4584DA http://wwwkeys.de.pgp.net > > -- > Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) > To make changes to your subscription: > > http://mail.postgresql.org/mj/mj_wwwusr?domain=postgresql.org&extra=pgsql-performance >
