From: | "Dan Langille" <dan(at)langille(dot)org> |
---|---|
To: | pgsql-performance(at)postgresql(dot)org |
Subject: | seq scan woes |
Date: | 2004-06-07 19:45:42 |
Message-ID: | 40C48DA6.3356.48DAC2EB@localhost |
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Thread: | |
Lists: | pgsql-performance |
A production system has had a query recently degrade in performance.
What once took < 1s now takes over 1s. I have tracked down the
problem to a working example.
Compare http://rafb.net/paste/results/itZIx891.html
with http://rafb.net/paste/results/fbUTNF95.html
The first shows the query as is, without much change (actually, this
query is nested within a larger query, but it demonstrates the
problem). The query time is about 1 second.
In the second URL, a "SET ENABLE_SEQSCAN TO OFF;" is done, and the
time drops to 151ms, which is acceptable.
What I don't understand is why the ports table is scanned in the
first place. Clues please?
--
Dan Langille : http://www.langille.org/
BSDCan - http://www.bsdcan.org/
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