Re: using extended statistics to improve join estimates

On 10/6/21 23:03, Zhihong Yu wrote:
> Hi,
>
> +       conditions2 = statext_determine_join_restrictions(root, rel, mcv);
> +
> +       /* if the new statistics covers more conditions, use it */
> +       if (list_length(conditions2) > list_length(conditions1))
> +       {
> +           mcv = stat;
>
> It seems conditions2 is calculated using mcv, I wonder why mcv is
> replaced by stat (for conditions1 whose length is shorter) ?
>

Yeah, that's wrong - it should be the other way around, i.e.

if (list_length(conditions1) > list_length(conditions2))

There's no test with multiple candidate statistics yet, so this went
unnoticed :-/

regards

--
Tomas Vondra
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