批量操作可以减少数据库与应用程序的交互次数，提高数据处理的吞吐量。本文将通过示例介绍如何批量插入、更新和删除数据。

您可以通过如下四种方法进行批量插入数据：

• 使用 INSERT INTO ... SELECT 的方法。

  postgres=# INSERT INTO tbl1 (id, info ,crt_time) SELECT GENERATE_SERIES(1,10000),'test',NOW();    
    INSERT 0 10000    
    postgres=# SELECT COUNT(*) FROM tbl1;    
     count     
    -------    
     10001    
    (1 row)

• 使用 VALUES(),(),...(); 的方法。

  postgres=# INSERT INTO tbl1 (id,info,crt_time) VALUES (1,'test',NOW()), (2,'test2',NOW()), (3,'test3',NOW());    
  INSERT 0 3

• 使用 BEGIN; ...多条INSERT...; END; 的方法。严格来说，这不属于批量，但可以减少事务提交时的同步等待，同样可以提升性能。

  postgres=# BEGIN;    
  BEGIN    
  postgres=# INSERT INTO tbl1 (id,info,crt_time) VALUES (1,'test',NOW());    
  INSERT 0 1    
  postgres=# INSERT INTO tbl1 (id,info,crt_time) VALUES (2,'test2',NOW());    
  INSERT 0 1    
  postgres=# INSERT INTO tbl1 (id,info,crt_time) VALUES (3,'test3',NOW());    
  INSERT 0 1    
  postgres=# END;    
  COMMIT

• 使用COPY协议。COPY协议与INSERT协议不一样，更加精简，插入效率高。

  test03=# \d test  
                    Table "public.test"  
      Column  |            Type             | Modifiers   
    ----------+-----------------------------+-----------  
     id       | integer                     | not null  
     info     | text                        |   
     crt_time | timestamp without time zone |   
    Indexes:  
        "test_pkey" PRIMARY KEY, btree (id)  
  
    test03=# COPY test FROM stdin;  
    Enter data to be copied followed by a newline.  
    End with a backslash and a period on a line by itself.  
    >> 8    'test'  '2017-01-01'  
    >> 9    'test9' '2017-02-02'  
    >> \.  
    COPY 2

  说明

  不同的语言驱动，对应的COPY接口不同，请参见如下文档：

  • PostgreSQL JDBC Driver - JDBC 4.2 9.4.1209 API
  • PostgreSQL 9.6.2 Documentation — Functions Associated with the COPY Command

test03=# UPDATE test SET info=tmp.info from (VALUES (1,'new1'),(2,'new2'),(6,'new6')) AS tmp (id,info) WHERE test.id=tmp.id;  
UPDATE 3  
test03=# SELECT * FROM test;  
 id |     info     |          crt_time            
----+--------------+----------------------------  
  3 | hello        | 2017-04-24 15:31:49.14291  
  4 | digoal0123   | 2017-04-24 15:42:50.912887  
  5 | hello digoal | 2017-04-24 15:57:29.622045  
  1 | new1         | 2017-04-24 15:58:55.610072  
  2 | new2         | 2017-04-24 15:28:20.37392  
  6 | new6         | 2017-04-24 15:59:12.265915  
(6 rows)

test03=# DELETE FROM test USING (VALUES (3),(4),(5)) AS tmp(id) WHERE test.id=tmp.id;  
DELETE 3  
test03=# SELECT * FROM test;  
 id |  info   |          crt_time            
----+---------+----------------------------  
  1 | new1    | 2017-04-24 15:58:55.610072  
  2 | new2    | 2017-04-24 15:28:20.37392  
  6 | new6    | 2017-04-24 15:59:12.265915

test03=# SET lock_timeout = '1s';
SET
test03=# TRUNCATE test;  
TRUNCATE TABLE  
test03=# SELECT * FROM test;  
 id | info | crt_time   
----+------+----------  
(0 rows)