Re: [PATCH] Overestimated filter cost and its mitigation

On Mon, Sep 11, 2017 at 04:43:46PM +0900, Yuto Hayamizu wrote:
> Hi hackers,
>
> Currently, cost of a filter with multiple clauses is estimated by
> summing up estimated cost of each clause. As long as a filter
> consists of simple clauses and its cost is fairly small, it works
> fine. However, when there exists some heavy clauses (like SubQuery or
> user-defined functions) and most of tuples are filtered by other
> simple clauses, total cost is likely to be overestimated. An attached
> patch mitigates this overestimation by using selectivity estimation of
> subsets of clauses in a filter.

I've taken the liberty of adding this to the upcoming commitfest.

Best,
David.
--
David Fetter <david(at)fetter(dot)org> http://fetter.org/
Phone: +1 415 235 3778 AIM: dfetter666 Yahoo!: dfetter
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