CREATE DOMAIN newint as int4;
CREATE TABLE tab (col newint unique);
ERROR:  data type newint has no default operator class for access method
"btree"
        You must specify an operator class for the index or define a
        default operator class for the data type


Specifically, GetDefaultOpClass() finds 0 exact matches and 3 binary
compatible matches.  Fetching getBaseType() of the attribute fixes the
problem for domains (see attachment).

Rod Taylor