On 2008-03-25 09:51, sathiya psql wrote: > Table size is nearly 700 MB, > and my machine had a 1 GB + 256 MB RAM, i had created the table space in > RAM, and then created this table in this RAM. > > So now everything is in RAM, if i do a count(*) on this table it returns > 327600 in 3 seconds, why it is taking 3 seconds ?????
PostgreSQL needs to scan the whole table. And 700MB is a lot of data even when in RAM. Check this: $ dd if=/dev/zero bs=1M count=700 | cat > /dev/null 734003200 bytes (734 MB) copied, 1.38732 s, 529 MB/s This command will just copy 700MB of zeros around in RAM, and it takes over 1s to do it on my Pentium D 3,4GHz. PostgreSQL would need to do much more with this data. Maybe you just got bitten by count(*) gotcha: http://sql-info.de/en/postgresql/postgres-gotchas.html#1_7 Maybe you'll get by with an estimate. Regards Tometzky -- ...although Eating Honey was a very good thing to do, there was a moment just before you began to eat it which was better than when you were... Winnie the Pooh -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
