On 2022-10-01 02:22:22 -0500, Ron wrote: > I extracted the singleton into a function, and that helped me isolate the > problem. I don't know what a singleton select is (duckduckgo tells me it has something to do with DB2 and/or COBOL, or maybe it's a whisky), but: > Note how quickly it runs the first five times, but takes 780x longer the > sixth time I run it. Exiting psql and entering again causes the same > slowness the sixth time it's run. PostgresSQL evaluates the exact plan the first 5 times it encounters the same prepared query. After that it switches to a generic plan if it thinks that the generic plan isn't worse than the specialized plans. If the plan suddenly gets worse after 5 executions, you've probably run into a case where the generic plan is worse although the cost computed by the planner isn't. hp -- _ | Peter J. Holzer | Story must make more sense than reality. |_|_) | | | | | hjp@xxxxxx | -- Charles Stross, "Creative writing __/ | http://www.hjp.at/ | challenge!"
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