pgsql: Defend against bogus parameterization of join input paths.

Defend against bogus parameterization of join input paths.

An outer join cannot be formed using an input path that is parameterized
by a value that is supposed to be nulled by the outer join. This is
obviously nonsensical, and it could lead to a bad plan being selected;
although currently it seems that we'll hit various sanity-check
assertions first.

I think that such cases were formerly prevented by the delay_upper_joins
mechanism, but now that that's gone we need an explicit check.

(Perhaps we should avoid generating baserel paths that could
lead to this situation in the first place; but it seems like
having a defense at the join level would be a good idea anyway.)

Richard Guo and Tom Lane, per report from Jaime Casanova

Discussion: https://postgr.es/m/CAJKUy5g2uZRrUDZJ8p-=giwcSHVUn0c9nmdxPSY0jF0Ov8VoEA@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/a798660ebe3ff1feb310db13b957c5cda4c8c50d

Modified Files
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src/backend/optimizer/path/joinpath.c | 33 +++++++++++++++++++++++++++++++++
src/test/regress/expected/join.out | 23 +++++++++++++++++++++++
src/test/regress/sql/join.sql | 22 ++++++++++++++++++++++
3 files changed, 78 insertions(+)