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Re: Todo: Teach planner to evaluate multiple windows in the optimal order - Mailing list pgsql-hackers

From John Naylor
Subject Re: Todo: Teach planner to evaluate multiple windows in the optimal order
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Msg-id CAFBsxsEz9k9K74uT0gfbW1xXnJme5+CVccWTx6_9kOnN-t8-Bg@mail.gmail.com
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In response to Re: Todo: Teach planner to evaluate multiple windows in the optimal order  (John Naylor <john.naylor@enterprisedb.com>)
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I wrote:
> it might be worthwhile to "zoom in" with more measurements, but haven't done that yet.

I've attached the script and image for 1 million / random / varying the mod by quarter-log intervals. Unfortunately I didn't get as good results as yesterday. Immediately going from mod 1 to mod 2, sort pushdown regresses sharply and stays regressed up until 10000. The tiebreaker patch helps but never removes the regression.

I suspect that I fat-fingered work_mem yesterday, so next I'll pick a badly-performing mod like 32, then range over work_mem and see if that explains anything, especially whether L3 effects are in fact more important in this workload.

--
John Naylor
EDB: http://www.enterprisedb.com
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