r function will be able to work
     successfully with a column named <TT
CLASS="LITERAL"
>key</TT
> even if it happens
     to have different types in different tables.
    </P
><P
>     Likewise, functions having polymorphic argument types have a separate
     statement cache for each combination of actual argument types they have
     been invoked for, so that data type differences do not cause unexpected
     failures.
    </P
><P
>    Statement caching can sometimes have surprising effects on the
    i