| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "Peterson, Bjorn" <Bjorn(dot)Peterson(at)pearson(dot)com> |
| Cc: | pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: enable_XXX options |
| Date: | 2005-04-01 16:36:43 |
| Message-ID: | 7068.1112373403@sss.pgh.pa.us |
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| Lists: | pgsql-performance |
"Peterson, Bjorn" <Bjorn(dot)Peterson(at)pearson(dot)com> writes:
> I have a query in my application that takes an unreasonable amount of time
> to complete (>4.5 hours execution time). After reviewing the EXPLAIN and
> EXPLAIN ANALYZE output for that and similar queries, my colleagues and I
> determined that turning off the enable_nestloop option might help - we
> noticed dramatic speed improvements for that specific query after doing so
> (<2 minutes execution time). I was warned not to mess with the enable_XXX
> options in a production environment, but does anyone see any problem with
> turning off the enable_nestloop option right before executing my query and
> turning it back on afterwards?
That's what it's there for ... but it would be useful to look into why
the planner gets it so wrong without that hint. Could we see EXPLAIN
ANALYZE both ways?
regards, tom lane
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