On Thu, May 7, 2009 at 10:14 AM, David Brain <dbr...@bandwidth.com> wrote:
> Hi, > > Some context, we have a _lot_ of data, > 1TB, mostly in 1 'table' - > the 'datatable' in the example below although in order to improve > performance this table is partitioned (by date range) into a number of > partition tables. Each partition contains up to 20GB of data (tens of > millons of rows), with an additional ~3GB of indexes, all this is > served off a fairly high performance server (8 core 32Gb, with FC > attached SAN storage). PostgreSQL version is 8.3.5 (running on 64bit > RHEL 5.2) > > This has been working reasonably well, however in the last few days > I've been seeing extremely slow performance on what are essentially > fairly simple 'index hitting' selects on this data. Have you re-indexed any of your partitioned tables? If you're index is fragmented, you'll be incurring extra I/O's per index access. Take a look at the pgstattuple contrib for some functions to determine index fragmentation. You can also take a look at the pg_stat_all_indexes tables. If your number of tup's fetched is 100 x more than your idx_scans, you *may* consider reindexing. --Scott
