PostgreSQL事务特性之ROLLBACK

一、回滚DDL

1. 回滚表的创建

postgres=# begin;
BEGIN
postgres=# create table test (id int, name text);
CREATE TABLE
postgres=# \dt
        List of relations
 Schema | Name | Type  |  Owner   
--------+------+-------+----------
 public | test | table | postgres
(1 row)

postgres=# rollback ;
ROLLBACK
postgres=# \dt
No relations found.

2. 回滚表结构的修改

postgres=# create table test (id int, name text);
CREATE TABLE
postgres=# begin ;   
BEGIN
postgres=# alter table test add column score int;
ALTER TABLE
postgres=# \d test 
     Table "public.test"
 Column |  Type   | Modifiers 
--------+---------+-----------
 id     | integer | 
 name   | text    | 
 score  | integer | 

postgres=# rollback ;
ROLLBACK
postgres=# \d test 
     Table "public.test"
 Column |  Type   | Modifiers 
--------+---------+-----------
 id     | integer | 
 name   | text    |

3. 回滚表的删除

postgres=# begin;
BEGIN
postgres=# drop table test ;
DROP TABLE
postgres=# \dt
No relations found.
postgres=# rollback ;
ROLLBACK
postgres=# \dt
        List of relations
 Schema | Name | Type  |  Owner   
--------+------+-------+----------
 public | test | table | postgres
(1 row)

4. 回滚表的清空

postgres=# insert into test values (1, 'a');
INSERT 0 1
postgres=# select * from test ;
 id | name 
----+------
  1 | a
(1 row)

postgres=# begin ;
BEGIN
postgres=# truncate test ;
TRUNCATE TABLE
postgres=# select * from test ;
 id | name 
----+------
(0 rows)

postgres=# rollback ;
ROLLBACK
postgres=# select * from test ;
 id | name 
----+------
  1 | a
(1 row)

5. 回滚索引的创建

postgres=# begin ;
BEGIN
postgres=# create index on test (id);
CREATE INDEX
postgres=# \d test
     Table "public.test"
 Column |  Type   | Modifiers 
--------+---------+-----------
 id     | integer | 
 name   | text    | 
Indexes:
    "test_id_idx" btree (id)

postgres=# rollback ;
ROLLBACK
postgres=# \d test 
     Table "public.test"
 Column |  Type   | Modifiers 
--------+---------+-----------
 id     | integer | 
 name   | text    |

6. 回滚索引的删除

postgres=# create index on test (id);
CREATE INDEX
postgres=# \d test
     Table "public.test"
 Column |  Type   | Modifiers 
--------+---------+-----------
 id     | integer | 
 name   | text    | 
Indexes:
    "test_id_idx" btree (id)

postgres=# begin ;
BEGIN
postgres=# drop index test_id_idx ;
DROP INDEX
postgres=# \d test 
     Table "public.test"
 Column |  Type   | Modifiers 
--------+---------+-----------
 id     | integer | 
 name   | text    | 

postgres=# rollback ;
ROLLBACK
postgres=# \d test
     Table "public.test"
 Column |  Type   | Modifiers 
--------+---------+-----------
 id     | integer | 
 name   | text    | 
Indexes:
    "test_id_idx" btree (id)

注意如果索引的创建和删除加了CONCURRENTLY，则不能放在事务里

postgres=# drop index test_id_idx ;
DROP INDEX
postgres=# \d test 
     Table "public.test"
 Column |  Type   | Modifiers 
--------+---------+-----------
 id     | integer | 
 name   | text    | 

postgres=# begin ;
BEGIN
postgres=# CREATE INDEX CONCURRENTLY ON test (id);
ERROR:  CREATE INDEX CONCURRENTLY cannot run inside a transaction block
postgres=# rollback ;
ROLLBACK
postgres=# \d test 
     Table "public.test"
 Column |  Type   | Modifiers 
--------+---------+-----------
 id     | integer | 
 name   | text    |

二、回滚DML

1. 回滚insert

postgres=# select * from test ;
 id | name 
----+------
  1 | a
(1 row)

postgres=# begin ;
BEGIN
postgres=# insert into test values (2, 'b');
INSERT 0 1
postgres=# select * from test ;
 id | name 
----+------
  1 | a
  2 | b
(2 rows)

postgres=# rollback ;
ROLLBACK
postgres=# select * from test ;
 id | name 
----+------
  1 | a
(1 row)

2. 回滚update

postgres=# select * from test ;
 id | name 
----+------
  1 | a
(1 row)

postgres=# begin ;
BEGIN
postgres=# update test set id = 2 where id = 1;
UPDATE 1
postgres=# select * from test ;
 id | name 
----+------
  2 | a
(1 row)

postgres=# rollback ;
ROLLBACK
postgres=# select * from test ;
 id | name 
----+------
  1 | a
(1 row)

3. 回滚delete

postgres=# select * from test ;
 id | name 
----+------
  1 | a
(1 row)

postgres=# begin ;
BEGIN
postgres=# delete from test where id = 1;
DELETE 1
postgres=# select * from test ;          
 id | name 
----+------
(0 rows)

postgres=# rollback ;
ROLLBACK
postgres=# select * from test ;
 id | name 
----+------
  1 | a
(1 row)