Re: domain on bit(N) type produces strange results

Kris Jurka <books@ejurka.com> writes:
> Creating a domain on bit(N) doesn't seem to work as expected when casting
> to the domain type.

> CREATE DOMAIN bit4 AS bit(4);

> SELECT 7::bit(4), 7::bit4;
>  bit  | bit4
> ------+------
>  0111 | 1000
> (1 row)

What's going on here is that "7::bit4" is implemented as
"7::bit::bit(4)", and since 7::bit is taken to mean 7::bit(1),
the result follows.

Bit is the only typmod-using datatype for which casting to the type
with typmod -1 risks discarding information.  In a brief look I'm
not sure whether this can easily be fixed without introducing unwanted
side-effects.

            regards, tom lane