> On Oct 26, 2020, at 1:20 PM, Michael Lewis <mle...@entrata.com> wrote:
>
> On Mon, Oct 26, 2020 at 11:14 AM Philip Semanchuk
> <phi...@americanefficient.com> wrote:
> >> The item I'm focused on is node 23. The estimate is for 7 rows, actual is
> >> 896 (multiplied by 1062 loops). I'm confused about two things in this node.
> >>
> >> The first is Postgres' estimate. The condition for this index scan
> >> contains three expressions --
> >>
> >> (five_uniform = zulu_five.five_uniform) AND
> >> (whiskey_mike = juliet_india.whiskey_mike) AND
> >> (bravo = 'mike'::text)
>
> Are the columns correlated? Have you tried to create extended statistics and
> see if the estimate changes? I believe that extended stats will not directly
> help with joins though, only group bys and perhaps choosing an index scan vs
> table scan when comparing the correlated columns to static values rather than
> joining up tables. Wouldn't be much effort to try it though.
There’s not a lot of correlation between whiskey_mike and bravo --
stxkind stxndistinct stxdependencies
['d', 'f'] {"7, 12": 42} {"12 => 7": 0.000274}
Those stats didn’t help the planner.
I should have mentioned that five_uniform has ~63k unique values, whereas
whiskey_mike has only 3, and bravo only 19.
Cheers
Philip
