PostgreSQL的串行与MySQL的自动增量?
我有一段MySQL:PostgreSQL的串行与MySQL的自动增量?,mysql,postgresql,auto-increment,postgresql-9.5,Mysql,Postgresql,Auto Increment,Postgresql 9.5,我有一段MySQL: CREATE TABLE seq_test ( id INT PRIMARY KEY AUTO_INCREMENT, name TEXT ); INSERT INTO seq_test(id, name) VALUES (1, 'one'); INSERT INTO seq_test(name) VALUES ('two'); 当我尝试在PostgreSQL中编写此代码时: CREATE TABLE seq_test ( id SERIAL PRIMARY
CREATE TABLE seq_test (
id INT PRIMARY KEY AUTO_INCREMENT,
name TEXT
);
INSERT INTO seq_test(id, name) VALUES (1, 'one');
INSERT INTO seq_test(name) VALUES ('two');
当我尝试在PostgreSQL中编写此代码时:
CREATE TABLE seq_test (
id SERIAL PRIMARY KEY,
name TEXT
);
INSERT INTO seq_test(id, name) VALUES (1, 'one');
INSERT INTO seq_test(name) VALUES ('two');
我得到以下错误:
[23505] ERROR: duplicate key value violates unique constraint "seq_test_pkey"
Detail: Key (id)=(1) already exists.
这是因为在PostgreSQL中,插入一个不会增加下一次插入的id。如何创建符合MySQL行为的表
这当然是一个人工示例,但我正在将一个大型代码库从MySQL移植到PostgreSQL,我无法控制的部分代码使用了两种样式,即带ID和不带ID,它们在MySQL中工作,但在PostgreSQL中不工作
一个丑陋的破解方法是总是选择setval'my_table_id_seq',从my_table中选择count*,真的…没有不好的解决方案:要么坚持串行功能,要么自己处理
但你让我感兴趣,我想出了一个稍微不那么粗俗的解决办法,我希望是:创造一个触发器来完成所有肮脏的工作
触发函数
添加了通知,以便我们可以看到发生了什么:
CREATE OR REPLACE FUNCTION update_seq_val_seq_test()
RETURNS TRIGGER AS $$
BEGIN
RAISE NOTICE 'id is %', NEW.id;
IF NEW.id > currval('seq_test_id_seq' :: REGCLASS)
THEN
RAISE NOTICE 'curval is %', currval('seq_test_id_seq' :: REGCLASS);
PERFORM setval('seq_test_id_seq' :: REGCLASS, (NEW.id) :: BIGINT);
RAISE NOTICE 'new curval is %', currval('seq_test_id_seq' :: REGCLASS); END IF;
RETURN NULL;
END;
$$
LANGUAGE 'plpgsql' COST 1;
设置触发器
扣动扳机
快速脏测试
tests2=# insert into seq_test (name) values ('first');
NOTICE: id is 30
INSERT 0 1
tests2=# select * from seq_test;
id | name
----+-------
30 | first
(1 row)
tests2=# select currval('seq_test_id_seq'::regclass);
currval
---------
30
(1 row)
tests2=# insert into seq_test (id, name) values (31, 'thirty one');
NOTICE: id is 31
NOTICE: curval is 30
NOTICE: new curval is 31
INSERT 0 1
tests2=# select currval('seq_test_id_seq'::regclass);
currval
---------
31
(1 row)
tests2=# select * from seq_test;
id | name
----+------------
30 | first
31 | thirty one
(2 rows)
tests2=# insert into seq_test (name) values ('thirty dunno what');
NOTICE: id is 32
INSERT 0 1
tests2=# insert into seq_test (id, name) values (21, 'back to the future');
NOTICE: id is 21
INSERT 0 1
tests2=# select currval('seq_test_id_seq'::regclass);
currval
---------
32
(1 row)
tests2=# select * from seq_test;
id | name
----+--------------------
30 | first
31 | thirty one
32 | thirty dunno what
21 | back to the future
(4 rows)
tests2=# insert into seq_test (name) values ('thirty dunno what++');
NOTICE: id is 33
INSERT 0 1
tests2=# select * from seq_test;
id | name
----+---------------------
30 | first
31 | thirty one
32 | thirty dunno what
21 | back to the future
33 | thirty dunno what++
(5 rows)
所以,现在Postgres更像你希望的那样处理这个案例,但是有很多事情需要为你检查:批量插入、回滚是如何工作的,这个触发器是如何影响性能的,对你来说还有更多的乐趣。@muistoshort:不幸的是,对于提供ID的代码,我无能为力。不管怎样,撇开实用性不谈,在这种情况下,让PostgreSQL表现得像MySQL最简单的方法是什么?
tests2=# insert into seq_test (name) values ('first');
NOTICE: id is 30
INSERT 0 1
tests2=# select * from seq_test;
id | name
----+-------
30 | first
(1 row)
tests2=# select currval('seq_test_id_seq'::regclass);
currval
---------
30
(1 row)
tests2=# insert into seq_test (id, name) values (31, 'thirty one');
NOTICE: id is 31
NOTICE: curval is 30
NOTICE: new curval is 31
INSERT 0 1
tests2=# select currval('seq_test_id_seq'::regclass);
currval
---------
31
(1 row)
tests2=# select * from seq_test;
id | name
----+------------
30 | first
31 | thirty one
(2 rows)
tests2=# insert into seq_test (name) values ('thirty dunno what');
NOTICE: id is 32
INSERT 0 1
tests2=# insert into seq_test (id, name) values (21, 'back to the future');
NOTICE: id is 21
INSERT 0 1
tests2=# select currval('seq_test_id_seq'::regclass);
currval
---------
32
(1 row)
tests2=# select * from seq_test;
id | name
----+--------------------
30 | first
31 | thirty one
32 | thirty dunno what
21 | back to the future
(4 rows)
tests2=# insert into seq_test (name) values ('thirty dunno what++');
NOTICE: id is 33
INSERT 0 1
tests2=# select * from seq_test;
id | name
----+---------------------
30 | first
31 | thirty one
32 | thirty dunno what
21 | back to the future
33 | thirty dunno what++
(5 rows)