select pg_constraint.conname as pk_name,pg_attribute.attname as colname,pg_type.typname as typename from

pg_constraint  inner join pg_class

on pg_constraint.conrelid = pg_class.oid

inner join pg_attribute on pg_attribute.attrelid = pg_class.oid

and  pg_attribute.attnum = pg_constraint.conkey[1]

inner join pg_type on pg_type.oid = pg_attribute.atttypid

where pg_class.relname = 'yourtablename'

and pg_constraint.contype='p'