Re: Re: BUG #18935: The optimiser's choice of sort doubles the execution time.

From: 萧鸿骏 <23031212454(at)stu(dot)xidian(dot)edu(dot)cn>
To: "Laurenz Albe" <laurenz(dot)albe(at)cybertec(dot)at>
Cc: pgsql-bugs(at)lists(dot)postgresql(dot)org
Subject: Re: Re: BUG #18935: The optimiser's choice of sort doubles the execution time.
Date: 2025-05-20 03:28:36
Message-ID: 2e178b46.15a.196ebbc6b43.Coremail.23031212454@stu.xidian.edu.cn
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2025-05-19 23:23:58 "Laurenz Albe" <laurenz(dot)albe(at)cybertec(dot)at> wrote：
>
> I see no bug here.
> The join condition is so complicated that the planner has a hard
> time estimating the number of result rows for the join.
> It guesses way to low, so the sort is expensive, and avoiding it is cheaper.
>
> The optimizer cannot be perfect, particularly in the face of complicated
> expressions like that.
>
> Yours,
> Laurenz Albe

Thank you for your answer! In the future I will avoid performance issues due to under-optimization of the optimizer.

regards,
hongjun xiao

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