Ian Barwick <barwick@gmx.net> writes:
> Is there any reason for the default value (31 characters?),
It's historical AFAIK.
> or are there
> any performance issues associated with longer values?
Larger values would definitely waste space in the system tables (since
type name is fixed-width). Bigger system tables = more I/O = some
amount of slowdown. I have not heard that anyone has tried to measure
the cost. It might be negligible; we just don't know.
I believe we'd be happy to change the number as soon as someone does the
legwork to quantify what it's going to cost.
regards, tom lane