pgsql: Fix misuse of RelOptInfo.unique_for_rels cache by SJE

Fix misuse of RelOptInfo.unique_for_rels cache by SJE

When SJE uses RelOptInfo.unique_for_rels cache, it passes filtered quals to
innerrel_is_unique_ext().  That might lead to an invalid match to cache entries
made by previous non self-join checking calls.  Add UniqueRelInfo.self_join
flag to prevent such cases.  Also, fix that SJE should require a strict match
of outerrelids to make sure UniqueRelInfo.extra_clauses are valid.

Reported-by: Alexander Lakhin
Discussion: https://postgr.es/m/4788f781-31bd-9796-d7d6-588a751c8787%40gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/30b4955a4668887044568743debef804b14418ca

Modified Files
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src/backend/optimizer/plan/analyzejoins.c | 30 +++++++++++++++++++++---------
src/include/nodes/pathnodes.h             |  6 ++++++
src/test/regress/expected/join.out        | 23 +++++++++++++++++++++++
src/test/regress/sql/join.sql             |  9 +++++++++
4 files changed, 59 insertions(+), 9 deletions(-)