Re: [BUGS] BUG #14753: Bad selectivity estimation with functional partial index - Mailing list pgsql-bugs

dilaz03@gmail.com writes:
> Postgres doesn't see corresponding stats tuple for functional partial
> index.

That's not a bug, it's intentional, per the comment in examine_variable():
                        * Has it got stats?  We only consider stats for                        * non-partial indexes,
sincepartial indexes probably                        * don't reflect whole-relation statistics; the above
        * check for uniqueness is the only info we take from                        * a partial index.
 

It's theoretically possible that we could do something useful with stats
from a partial index, but it would require a lot of shaky assumptions
I'm afraid.
        regards, tom lane


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