Field size become unlimited in union...

Hello!

As I experienced, PGSQL changes the result field sizes to unlimited
varchar, when I passed different field size in same column of the union.

SP.Key - varchar(100)
SP.Value - varchar(200)

Example:

select 'a', value from sp
union all
select key, value from sp

The first field is not limited to 100, it's unlimited varchar() (= Text,
Memo, CLOB).

So PG don't use the maximal field size (100).

If I did cast on the field to resize to 100, the result is limited
correctly.

select cast('a' as varchar(100)), value from sp
union all
select key, value from sp

Can I force somehow to PG use the maximal size?

Or must I know and equalize all field sizes in union?

Or must I use temporary tables and inserts to not get this problem?

Thanks

Regards
dd