select
    distinct(constraint_name) CONSTRAINT_NAME
from
    information_schema.key_column_usage
where
    constraint_name in (
    select
	rc.constraint_name
    from
	information_schema.referential_constraints rc
    inner join information_schema.table_constraints tc on
	tc.constraint_name = rc.constraint_name
    inner join information_schema.table_constraints tc2 on
	tc2.constraint_name = rc.unique_constraint_name
    where
	tc2.constraint_type = 'PRIMARY KEY')
    and lower(column_name) like 'xxx_%';