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)

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)