This is because the constraint names that are normally used to find foreign key relationships are unfortunately not unique in the information_schema provided in postgresql. For this reason we need to dig deeper in pg catalog to get the correct constraint names. In 1.1 the constraint names where extracted from the table definitions which assumes that foreign keys are all in the same schema. This may not always be the case.

http://www.postgresql.org/message-id/26677.1086673982@sss.pgh.pa.us