PostgreSQL query that finds columns and referenced columns from a constraint

find_contraint_ref_fields.sql

WITH constraint_ref_fields AS (
	SELECT 
		unnest(con1.conkey) AS local_key, 
		unnest(con1.confkey) AS ref_key, 		 
		con1.conrelid, 
		con1.confrelid
	FROM 
		pg_class cl 
		JOIN pg_namespace ns ON cl.relnamespace = ns.oid 
		JOIN pg_constraint con1 ON con1.conrelid = cl.oid 
	WHERE 	
		con1.oid = ? --constraint oid
) 
SELECT 
	att.attname AS local_column, 
	att2.attname AS ref_column 
FROM
	constraint_ref_fields con 
JOIN pg_attribute att ON att.attrelid = con.conrelid AND att.attnum = con.local_key
LEFT JOIN pg_attribute att2 ON att2.attrelid = con.confrelid AND att2.attnum = con.ref_key;