Re: GIN disagrees with seq scan when NOT and AND operators are combined

Chinmay Kanchi <cgkanchi(at)gmail(dot)com> writes:
> When working on pg_lion (https://github.com/cgkanchi/pg_lion) I stumbled
> upon a bug where GIN returns fewer rows when multiple ! operators are
> specified. I was able to repro this on all versions from 16 to trunk.

Thanks for the report. (For the archives' sake, note this repro
requires "set enable_seqscan = 0", else you get a seqscan plan
and no bug.)

I'm not too familiar with this code, but it looks like
extract_jsp_bool_expr concludes that !($.b == 20) is not supported
as a GIN scan condition, and then the next recursion level up does
the wrong thing with the negated && condition. The attached quick
hack seems to fix it. I didn't look around for other instances
of the same thinko, but there might be some.

regards, tom lane