Обсуждение: pgsql: Adjust the description of locking to clarify that locks held by a

Log Message:
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Adjust the description of locking to clarify that locks held by a
subtransaction are released if the subtransaction aborts --- in user-level
terminology, this means either rolling back to a savepoint or escaping from
a plpgsql exception block.  Per recent suggestion from Simon.

Modified Files:
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    pgsql/doc/src/sgml:
        mvcc.sgml (r2.64 -> r2.65)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/mvcc.sgml.diff?r1=2.64&r2=2.65)