You're right .
I will begin by migrate postgresql version.
postgresql is now to 8.3 version . A lot of performance inprovements
have been made in this last version .
In any case I must do a pg_dump/pg_restore.
So , Should I try directly 8.3 version or is it more cautious to stay in
8.1.x version ?
Olivier
Scott Marlowe a écrit :
On Dec 19, 2007 1:57 AM, olivier boissard <olivier.boissard@xxxxxxxxx> wrote:
Scott Marlowe a écrit :
On Dec 18, 2007 4:21 PM, olivier.boissard@xxxxxxxxx
<olivier.boissard@xxxxxxxxx> wrote:
Hello,
My purpose is to uses different query plan depending on queries
I got the following problem : some queries are taking too much time and
postgresql does not take the most relevant index in account.
I search on internet and found that no HINT function was available in
postgresl.
I tried to change indexes parameters in postgresql.conf but eache time I
set a param to OFF (example nested_loop ,seqscan, ...) , some queries
freeze database .
How can we force postgresql to use a plan ?
That's not how we do things in postgresql land (usually).
You should figure out WHY your queries are picking the wrong plan, and
then see if you can get them to pick the right ones. If it's a query
planner bug, you report it here, or the perform or general lists, and
it gets fixed. Generic hints aren't likely to happen any time soon,
although I do believe 8.3 is introducing function costing of some
kind, which seems like a useful idea.
But, back to fixing your slow queries.
1: Increase statistics targets on the guilty columns and reanalyze.
2: Run explain analyze select.... and post the output here.
3: ???
4: profit?
Thanks for reply
I will extract some queries.
I want to precise that I use postgresql 8.1.0 .
First step would be to update to the latest 8.1.x version, whatever
that is. There have been a LOT of fixes in the 8.1 branch since 8.1.0
came out, and one might be a fix for your query problem. minor
updates are strictly bug and security fixes, so they're not likely to
cause any problems.
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