pgsql: Prevent Parallel Hash Join for JOIN_UNIQUE_INNER.

Prevent Parallel Hash Join for JOIN_UNIQUE_INNER.

WHERE EXISTS (...) queries cannot be executed by Parallel Hash Join
with jointype JOIN_UNIQUE_INNER, because there is no way to make a
partial plan totally unique.  The consequence of allowing such plans
was duplicate results from some EXISTS queries.

Back-patch to 11.  Bug #15857.

Author: Thomas Munro
Reviewed-by: Tom Lane
Reported-by: Vladimir Kriukov
Discussion: https://postgr.es/m/15857-d1ba2a64bce0795e%40postgresql.org

Branch
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REL_11_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/14d8b539d3bd4cf9faf65ca86a733bada202107f

Modified Files
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src/backend/optimizer/path/joinpath.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)