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Appending "LIMIT" to query drastically decreases performance
- From: cluster <skrald(at)amossen(dot)dk>
- To: pgsql-performance(at)postgresql(dot)org
- Subject: Appending "LIMIT" to query drastically decreases performance
- Date: Fri, 30 Nov 2007 12:16:08 +0100
- Message-id: <fiordm$2aev$1@news.hub.org> <text/plain>
Can anyone explain the following odd behavior?I have a query that completes in about 90 ms. If I append LIMIT to the very end, eg. "LIMIT 500" the evaluation time increases to about 800 ms. How can performance get *worse* by giving the database the option to stop the evaluation earlier (when it reaches the output 500 rows)?
I have pasted both queries together with output from explain analyze here: http://pastebin.com/m3c0d1896
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