Re: [PATCH] fix GIN index search sometimes losing results

Pavel Borisov <pashkin.elfe@gmail.com> writes:
> It appeared than GIN index sometimes lose results if simultaneously:
> 1 if query operand contains weight marks
> 2 if weight-marked operand is negated by ! operator
> 3 if there are only logical (not phrase) operators from this negation
> towards the root of query tree.

Nice catch ... but if you try it with a GIST index, that fails too.

Even if it were only GIN indexes, this patch is an utter hack.
It might accidentally work for the specific case of NOT with
a single QI_VAL node as argument, but not for anything more
complicated.

I think the root of the problem is that if we have a query using
weights, and we are testing tsvector data that lacks positions/weights,
we can never say there's definitely a match.  I don't see any decently
clean way to fix this without redefining the TSExecuteCallback API
to return a tri-state YES/NO/MAYBE result, because really we need to
decide that it's MAYBE at the level of processing the QI_VAL node,
not later on.  I'd tried to avoid that in e81e5741a, but maybe we
should just bite that bullet, and not worry about whether there's
any third-party code providing its own TSExecuteCallback routine.
codesearch.debian.net suggests that there are no external callers
of TS_execute, so maybe we can get away with that.

            regards, tom lane