  </P
><P
>       It is recommended that in a <TT
CLASS="LITERAL"
>UNIQUE_CHECK_EXISTING</TT
> call,
       the access method further verify that the target row actually does
       have an existing entry in the index, and report error if not.  This
       is a good idea because the index tuple values passed to
       <CODE
CLASS="FUNCTION"
>aminsert</CODE
> will have been recomputed.  If the index
       definition involves functions that are not really immutable, we
       might be checking the wrong area