Re: Fix gin index cost estimation

From: Ronan Dunklau <ronan(dot)dunklau(at)aiven(dot)io>
To: Alexander Korotkov <aekorotkov(at)gmail(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Michael Paquier <michael(at)paquier(dot)xyz>, pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: Fix gin index cost estimation
Date: 2022-12-02 12:58:27
Message-ID: 10184681.nUPlyArG6x@aivenlaptop
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Le vendredi 2 décembre 2022, 12:33:33 CET Alexander Korotkov a écrit :
> Hi, Ronan!
> Thank you for your patch. Couple of quick questions.
> 1) What magic number 50.0 stands for? I think we at least should make
> it a macro.

This is what is used in other tree-descending estimation functions, so I used
that too. Maybe a DEFAULT_PAGE_CPU_COST macro would work for both ? If so I'll
separate this into two patches, one introducing the macro for the other
estimation functions, and this patch for gin.

> 2) "We only charge one data page for the startup cost" – should this
> be dependent on number of search entries?

Good point, multiplying it by the number of search entries would do the trick.

Thank you for looking at this !


Ronan Dunklau

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