I wrote:
> Robert Haas <robertmh...@gmail.com> writes:
>> But we could also find some way to assert that the parameterization
>> sets contain only top-most rels.
> Hmm ... perhaps worth doing. I think bms_is_subset against
> all_baserels would work.
[ tries that ... ] Nope, it needs to be all_query_rels. I plead
ENOCAFFEINE. However, while we could easily add
+ Assert(bms_is_subset(inner_paramrels, root->all_query_rels));
+ Assert(bms_is_subset(outer_paramrels, root->all_query_rels));
to try_nestloop_path, that doesn't work as-is in
calc_non_nestloop_required_outer because we don't pass "root" to it.
We could add that, or perhaps contemplate some more-extensive
rearrangement to make the division of labor between
calc_nestloop_required_outer and its caller more like that between
calc_non_nestloop_required_outer and its callers. But I'm feeling
kind of unenthused about that, because
(1) I don't see how to rearrange things without duplicating code:
try_nestloop_path needs access to some of these values, while moving
any work out of calc_non_nestloop_required_outer would mean two
copies in its two callers. So there are reasons why that's not
perfectly symmetric. (But I still maintain that we should try to
make the code look similar between these two code paths, when
considering both the calc_xxx functions and their callers.)
(2) joinpath.c already knows that parameterization sets mention
only top-level relids, specifically at the definition and uses of
PATH_PARAM_BY_PARENT, and I bet there are more dependencies elsewhere.
So I'm not sure about the value of asserting it only here.
In short I'm inclined to apply v3 as-is.
regards, tom lane
