constraint issues

lib/postgres.js

@@ -22,6 +22,7 @@ var Postgres = function(connection){
          information_schema.table_constraints tc  \
       where                                       \
         cu.constraint_name = tc.constraint_name   \
+        and tc.constraint_type = 'PRIMARY KEY'    \
       and tc.table_name = ist.table_name          \
     ) as pk                                       \
     from information_schema.tables ist            \