学习目标：学习openGauss事务控制
课程内容：
事务是用户定义的一个数据库操作序列，这些操作要么全做要么全不做，是一个不可分割的工作单位
部分学习内容如下：
课程作业：
1.以默认方式启动事务1，修改事务隔离级别，查看transaction_isolation
omm=# start transaction;
START TRANSACTION
omm=# select * from pg_class limit 1;
relname | relnamespace | reltype | reloftype | relowner | relam | relfilenode | reltablespace | relpages | reltuples | r
elallvisible | reltoastrelid | reltoastidxid | reldeltarelid | reldeltaidx | relcudescrelid | relcudescidx | relhasindex | rel
isshared | relpersistence | relkind | relnatts | relchecks | relhasoids | relhaspkey | relhasrules | relhastriggers | relhassu
bclass | relcmprs | relhasclusterkey | relrowmovement | parttype | relfrozenxid | relacl | reloptions | relrepliden
t | relfrozenxid64 | relbucket | relbucketkey
--------------+--------------+---------+-----------+----------+-------+-------------+---------------+----------+-----------+--
-------------+---------------+---------------+---------------+-------------+----------------+--------------+-------------+----
---------+----------------+---------+----------+-----------+------------+------------+-------------+----------------+---------
-------+----------+------------------+----------------+----------+--------------+-------------------+------------+------------
18 | 2840 | 0 | 0 | 0 | 0 | 0 | t | f
| p | r | 29 | 0 | f | f | f | f | f
| 0 | f | f | n | 0 | {omm=arwdDxt/omm} | | n
--+----------------+-----------+--------------
pg_statistic | 11 | 11334 | 0 | 10 | 0 | 13689 | 0 | 18 | 476 |
| 7891 | |
(1 row)
omm=# end;
COMMIT
omm=# start transaction isolation level repeatable read read write;
START TRANSACTION
omm=# show transaction_isolation;
transaction_isolation
-----------------------
repeatable read
(1 row)
omm=# rollback;
ROLLBACK
2.以读写方式启动事务2，创建新表，修改事务为只读事务，查看transaction_read_only，并向表中插入记录
omm=# start transaction isolation level read committed read write;
omm=# START TRANSACTION
create table product(id int,name char(20));
CREATE TABLE
omm=# set local transaction isolation level read committed read only;
SET
omm=# show transaction_isolation;
transaction_isolation
-----------------------
read committed
(1 row)
omm=# insert into product values(1,'open');
ERROR: cannot execute INSERT in a read-only transaction
omm=# rollback;
ROLLBACK
3.启动事务3，对表进行增删改查，并用到创建savepoint，回滚savepoint和删除savepoint
omm=# start transaction;
START TRANSACTION
omm=# insert into products values(0);
INSERT 0 1
omm=# savepoint my_point;
omm=# SAVEPOINT
insert into products values(1);
INSERT 0 1
omm=# rollback to savepoint my_point;
ROLLBACK
omm=# select * from products;
id
----
0
(1 row)
omm=# release savepoint my_point;
RELEASE
omm=# insert into products values(5);
INSERT 0 1
omm=# select * from products;
id
----
0
5
(2 rows)
omm=# commit;
COMMIT
4.清理数据
omm=# drop table products;
DROP TABLE
