Re: [GENERAL] more problems with count(*) on large table

1. 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.

-- 
Alvaro Herrera                                
http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.

---------------------------(end of broadcast)---------------------------
TIP 9: In versions below 8.0, the planner will ignore your desire to
       choose an index scan if your joining column's datatypes do not
       match