er, ...);
CREATE TABLE child1000(check (key between 1000 and 1999)) INHERITS(parent);
CREATE TABLE child2000(check (key between 2000 and 2999)) INHERITS(parent);
...
SELECT * FROM parent WHERE key = 2400;</PRE
><P>

        With constraint exclusion enabled, this <TT
CLASS="COMMAND"
>SELECT</TT
>
        will not scan <TT
CLASS="STRUCTNAME"
>child1000</TT
> at all, improving performance.
       </P
><P
>        Currently, constraint exclusion is enabled by default
        only for cases that are often used 