pgsql: Partially roll back overenthusiastic SSI optimization.

Partially roll back overenthusiastic SSI optimization.

When a regular lock is held, SSI can use that in lieu of a predicate lock
to detect rw conflicts; but if the regular lock is being taken by a
subtransaction, we can't assume that it'll commit, so releasing the
parent transaction's lock in that case is a no-no.

Kevin Grittner

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/fbc0d07796bcae8b2ee4b09ed236877338c95130

Modified Files
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src/backend/storage/lmgr/predicate.c |   20 +++++++++++++-------
1 files changed, 13 insertions(+), 7 deletions(-)