PostgreSQL批量获取序列的最近值

做Postgresql的迁移或者做多主，两边需要序列错开时，分别列出数据库序列的所有值做检查是一件很有必要的事情。

可以用以下函数来列出当前DB的所有序列的最后一个值

CREATE OR REPLACE FUNCTION fun_list_seq() 
RETURNS TABLE(schema_name text,seq_name text,last_val bigint,increment_by bigint) 
AS
$body$
DECLARE
  sequence_name varchar(255);
  schema_name   text;
BEGIN
  FOR sequence_name,schema_name in SELECT relname,nspname FROM pg_class a,pg_namespace b WHERE a.relnamespace = b.oid and a.relkind = 'S'
  LOOP
  RETURN QUERY EXECUTE  'SELECT ' ||quote_literal(schema_name)||'::text,'|| quote_literal(sequence_name) || '::text,last_value,increment_by FROM ' || quote_ident(sequence_name) ;
  END LOOP;
  RETURN;
END
$body$
LANGUAGE 'plpgsql';

实现效果

[postgres@localhost ~]$ psql db_ken
psql (9.4beta2)
Type "help" for help.

db_ken=# select * from fun_list_seq() ;
 schema_name |    seq_name    | last_val | increment_by 
-------------+----------------+----------+--------------
 public      | t2_id_seq      |       49 |            2
 public      | tbl_ken_id_seq |       20 |            1
 public      | t_id_seq       |       49 |            2
 bucardo     | t_id_seq       |       49 |            2
(4 rows)

db_ken=# \q