Обсуждение: pgsql: Improve create_unique_path to not be fooled by unrelated clauses

Log Message:
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Improve create_unique_path to not be fooled by unrelated clauses that happen
to be syntactically part of a semijoin clause.  For example given
WHERE EXISTS(SELECT ... WHERE upper.var = lower.var AND some-condition)
where some-condition is just a restriction on the lower relation, we can
use unique-ification on lower.var after having applied some-condition within
the scan on lower.

Modified Files:
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    pgsql/src/backend/optimizer/util:
        pathnode.c (r1.149 -> r1.150)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/util/pathnode.c?r1=1.149&r2=1.150)