postgreSQL外键引用查询

根据一个表名，查询所有外键引用它的表，以及那些外键的列名
key_column_usage（系统列信息表），
pg_constraint（系统所有约束表）

SELECT  x.table_name,
	    x.column_name
  FROM  information_schema.key_column_usage x
  INNER JOIN  (SELECT  t.relname, 
                       a.conname 
                 FROM  pg_constraint a 
                 INNER JOIN pg_class ft
                         ON ft.oid = a.confrelid 
                 INNER JOIN pg_class t 
                         ON t.oid = a.conrelid
                WHERE  a.contype = 'f' 
                  AND  a.confrelid =
                       (select e.oid 
                          from pg_class e
                         where e.relname = 'xxx_table')
                ) tp 
          ON (x.table_name = tp.relname AND
              x.constraint_name = tp.conname)