P
></P><UL
><LI
><P
>       If a conflicting valid row has been deleted by the current transaction,
       it's okay.  (In particular, since an UPDATE always deletes the old row
       version before inserting the new version, this will allow an UPDATE on
       a row without changing the key.)
      </P
></LI
><LI
><P
>       If a conflicting row has been inserted by an as-yet-uncommitted
       transaction, the would-be inserter must wait to see if that transaction
       commits.  If it rolls back then t