here is no conflict.  If it commits
       without deleting the conflicting row again, there is a uniqueness
       violation.  (In practice we just wait for the other transaction to
       end and then redo the visibility check in toto.)
      </P
></LI
><LI
><P
>       Similarly, if a conflicting valid row has been deleted by an
       as-yet-uncommitted transaction, the would-be inserter must wait
       for that transaction to commit or abort, and then repeat the test.
      </P
></LI
></UL
><P>
  </P
>