Gbase 8a数据库集群，V8版本不支持一个session事务内对同一个表的多次DML操作，必须先commmit或rollback才可以。在V95版本里，提供了这个功能。
事务配置参数
管理节点增加或修改如下配置
gcluster_transaction_disable=0
数据节点增加或修改如下配置
gbase_tx_log_mode=USE,STANDARD_TRANS
测试用例
如下提供一个事务内，对单表和多表做多个变动的样例。 其中多表更新一旦有并发时，请一定注意【死锁】问题，毕竟严格角度讲，8a支持的事务还是非常非常弱的。
单表多次DML变动
如下演示了一个表，开启事务后，连续做insert,update,delete,load的效果。
[gbase@localhost ~]$ gccli testdb Gbase client 9.5.2.26.121440. Copyright (c) 2004-2020, Gbase. All Rights Reserved. gbase> set autocommit=0; Query OK, 0 rows affected (Elapsed: 00:00:00.00) gbase> select * from t1; +------+ | id | +------+ | 99 | +------+ 1 row in set (Elapsed: 00:00:00.01) gbase> insert into t1 values(1); Query OK, 1 row affected (Elapsed: 00:00:00.00) gbase> select * from t1; +------+ | id | +------+ | 99 | | 1 | +------+ 2 rows in set (Elapsed: 00:00:00.01) gbase> rollback; Query OK, 0 rows affected (Elapsed: 00:00:00.51) gbase> select * from t1; +------+ | id | +------+ | 99 | +------+ 1 row in set (Elapsed: 00:00:00.01) gbase> insert into t1 values(1); Query OK, 1 row affected (Elapsed: 00:00:00.00) gbase> select * from t1; +------+ | id | +------+ | 99 | | 1 | +------+ 2 rows in set (Elapsed: 00:00:00.01) gbase> update t1 set id=98 where id=99; Query OK, 1 row affected (Elapsed: 00:00:00.08) Rows matched: 1 Changed: 1 Warnings: 0 gbase> select * from t1; +------+ | id | +------+ | 98 | | 1 | +------+ 2 rows in set (Elapsed: 00:00:00.00) gbase> rollback; Query OK, 0 rows affected (Elapsed: 00:00:00.51) gbase> select * from t1; +------+ | id | +------+ | 99 | +------+ 1 row in set (Elapsed: 00:00:00.01) gbase> insert into t1 values(1); Query OK, 1 row affected (Elapsed: 00:00:00.00) gbase> load data infile 'sftp://gbase:gbase1234@10.0.2.101/home/gbase/t.txt' into table t1; Query OK, 1 row affected (Elapsed: 00:00:01.17) Task 1028 finished, Loaded 1 records, Skipped 0 records gbase> select * from t1; +------+ | id | +------+ | 99 | | 8888 | | 1 | +------+ 3 rows in set (Elapsed: 00:00:00.01) gbase> rollback; Query OK, 0 rows affected (Elapsed: 00:00:00.52) gbase> select * from t1; +------+ | id | +------+ | 99 | +------+ 1 row in set (Elapsed: 00:00:00.01) gbase> insert into t1 values(1); Query OK, 1 row affected (Elapsed: 00:00:00.00) gbase> select * from t1; +------+ | id | +------+ | 99 | | 1 | +------+ 2 rows in set (Elapsed: 00:00:00.00) gbase> load data infile 'sftp://gbase:gbase1234@10.0.2.101/home/gbase/t.txt' into table t1; Query OK, 1 row affected (Elapsed: 00:00:01.06) Task 1029 finished, Loaded 1 records, Skipped 0 records gbase> select * from t1; +------+ | id | +------+ | 99 | | 1 | | 8888 | +------+ 3 rows in set (Elapsed: 00:00:00.01) gbase> commit; Query OK, 0 rows affected (Elapsed: 00:00:00.03) gbase> select * from t1; +------+ | id | +------+ | 99 | | 1 | | 8888 | +------+ 3 rows in set (Elapsed: 00:00:00.00) gbase> rollback; Query OK, 0 rows affected (Elapsed: 00:00:00.50) gbase> select * from t1; +------+ | id | +------+ | 99 | | 1 | | 8888 | +------+ 3 rows in set (Elapsed: 00:00:00.00)
多表各自多次DML变动
如下演示一个事务内，对多个表各自做DML操作的效果。
gbase> set autocommit=0; Query OK, 0 rows affected (Elapsed: 00:00:00.00) gbase> insert into t2 select * from t1; Query OK, 3 rows affected (Elapsed: 00:00:00.06) Records: 3 Duplicates: 0 Warnings: 0 gbase> select * from t2; +------+---------------------+ | id | name | +------+---------------------+ | 1 | 2019-08-23 10:02:23 | | 3 | third | | 456 | '456456' | +------+---------------------+ 3 rows in set (Elapsed: 00:00:00.01) gbase> update t1 set name='333333' where id=3; Query OK, 1 row affected (Elapsed: 00:00:00.02) Rows matched: 1 Changed: 1 Warnings: 0 gbase> select * from t1; +------+---------------------+ | id | name | +------+---------------------+ | 1 | 2019-08-23 10:02:23 | | 3 | 333333 | | 456 | '456456' | +------+---------------------+ 3 rows in set (Elapsed: 00:00:00.01) gbase> update t2,t1 set t2.name=t1.name where t1.id=t2.id; Query OK, 3 rows affected (Elapsed: 00:00:00.18) Rows matched: 3 Changed: 3 Warnings: 0 gbase> select * from t2; +------+---------------------+ | id | name | +------+---------------------+ | 1 | 2019-08-23 10:02:23 | | 3 | 333333 | | 456 | '456456' | +------+---------------------+ 3 rows in set (Elapsed: 00:00:00.00) gbase> update t2,t1 set t2.name=t1.name where t1.id=t2.id; Query OK, 3 rows affected (Elapsed: 00:00:00.28) Rows matched: 3 Changed: 3 Warnings: 0 gbase> select * from t2; +------+---------------------+ | id | name | +------+---------------------+ | 1 | 2019-08-23 10:02:23 | | 3 | 333333 | | 456 | '456456' | +------+---------------------+ 3 rows in set (Elapsed: 00:00:00.00) gbase> select * from t1; +------+---------------------+ | id | name | +------+---------------------+ | 1 | 2019-08-23 10:02:23 | | 3 | 333333 | | 456 | '456456' | +------+---------------------+ 3 rows in set (Elapsed: 00:00:00.01) gbase> commit; Query OK, 0 rows affected (Elapsed: 00:00:00.10)
总结
非必要的前提下，还是不建议使用事务功能，特别是并发使用。
对同一个表，一个事务内的多次更新可以支持，但多个连接session的同一个表的并发更新还是不支持的。
