am Fri, dem 28.09.2007, um 12:50:34 -0400 mailte Alvaro Herrera folgendes: > A. Kretschmer wrote: > > am Fri, dem 28.09.2007, um 11:56:46 -0400 mailte Mike Charnoky folgendes: > > > Hi, > > > > > > I am still having problems performing a count(*) on a large table. This > > > > > > Now, certain count(*) queries are failing to complete for certain time > > > ranges (I killed the query after about 24 hours). The table is indexed > > > on a timestamp field. Here is one query that hangs: > > > > Again: an index can't help! Because of MVCC: 'select count(*)' without > > WHERE-condition forces an seq. table-scan. > > But he does have a WHERE condition. THe problem is, probably, that the > condition is not selective enough so the planner chooses to do a > seqscan. Yes, i'm sorry, i havn't recognize this. Maybe wrong statistics. As Andrew suggested, a 'ALTER TABLE...SET STATISTICS' can help. Andreas -- Andreas Kretschmer Kontakt: Heynitz: 035242/47150, D1: 0160/7141639 (mehr: -> Header) GnuPG-ID: 0x3FFF606C, privat 0x7F4584DA http://wwwkeys.de.pgp.net ---------------------------(end of broadcast)--------------------------- TIP 4: Have you searched our list archives? http://archives.postgresql.org/
