In response to Laurent Manchon <lmanchon@xxxxxxxxxxxxxx>: > > I have a slow response of my PostgreSQL database 7.4 using this query below > on a table with 800000 rows: > > select count(*)from tbl; > > PostgreSQL return result in 28 sec every time. > although MS-SQL return result in 0.02 sec every time. > > My server is a DELL PowerEdge 2600 with bi-processor Xeon at 3.2 Ghz > with 3GBytes RAM While there's truth in everything that's been said by others, the query should not take _that_ long. I just tried a count(*) on a table with 460,000 rows, and it took less than a second. count(*) in PostgreSQL is not likely to compare to most other RDBMS for the reasons others have stated, but counting 800,000 rows shouldn't take 28 seconds. The standard question applies: have you vacuumed recently? > My PostgreSQL Conf is > ********************* > log_connections = yes > syslog = 2 > effective_cache_size = 50000 > sort_mem = 10000 > max_connections = 200 > shared_buffers = 3000 > vacuum_mem = 32000 > wal_buffers = 8 > max_fsm_pages = 2000 > max_fsm_relations = 100 > > Can you tell me is there a way to enhence performance ? On our 4G machines, we use shared_buffers=240000 (which equates to about 2G). The only reason I don't set it higher is that FreeBSD has a limit on shared memory of 2G. The caveat here is that I'm running a mix of 8.1 and 8.2. There have been significant improvements in both the usage of shared memory, and the optimization of count(*) since 7.4, so the first suggestion I have is to upgrade your installation. -- Bill Moran Collaborative Fusion Inc.
