Carlo Stonebanks wrote:
Just a wild guess, but the performance problem sounds like maybe as your
data changes, eventually the planner moves some query from an index scan
to a sequential scan, do you have any details on what queries are taking
so long when things are running slow? You can turn on the GUC var
"log_min_duration_statement" and see what queries are slow and then
manually check them with an explain analyze, that might help.
This is pretty well what I think is happening - I expect all queries to
eventually move from seq scans to index scans. I actually have a SQL logging
opion built into the import app.
I just can't figure out how the planner can be so wrong. We are running a 4
CPU server (two dual core 3.2 GHz Xeons) with 4GB RAM and Windows Server
2003 x64 and a PERC RAID subsystem (I don't know the RAID type). I know that
the metrics for the planner can be changed - is the default config for
postgesql not suitable for our setup? For this server, we would like to be
optimised for high speed over a few connections, rather than the classic
balanced speed over many connections.
If it is the planner choosing a very bad plan, then I don't think your
hardware has anything to do with it. And, we can't diagnose why the
planner is doing what it's doing without a lot more detail. I suggest
you do something to figure out what queries are taking so long, then
send us an explain analyze, that might shine some light on the subject.
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