MyCat：第六章：MyCAT自增字段和返回生成的主键ID的经验分享

MyCAT自增字段和返回生成的主键ID的经验分享 说明： 1、mysql本身对非自增长主键，使用last_insert_id()是不会返回结果的，只会返回0. 2、mysql只会对定义自增长主键，可以用last_insert_id()返回主键值。

mycat目前提供了自增长主键功能，但是如果对应的mysql节点上数据表，没有定义auto_increment， 那么在mycat层调用last_insert_id()也是不会返回结果的。 正确使用方式如下： 1、mysql定义自增主键 CREATE TABLE `tt2` (   `id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,   `nm` INT(10) UNSIGNED NOT NULL,   PRIMARY KEY (`id`) ) ENGINE=MYISAM AUTO_INCREMENT=6 DEFAULT CHARSET=utf8; 2、mycat定义自增 [root@test conf]# vim schema.xml <?xml version="1.0"?> <!DOCTYPE mycat:schema SYSTEM "schema.dtd"> <mycat:schema xmlns:mycat="http://org.opencloudb/">

        <schema name="TESTDB" checkSQLschema="false" sqlMaxLimit="100">             <!-- random sharding using mod sharind rule -->         <!-- autoIncrement="true" 属性-->             <table name="tt2" primaryKey="id" autoIncrement="true" dataNode="dn1,dn2,dn3,dn4,dn5" rule="mod-long" />             <table name="mycat_sequence" primaryKey="name" dataNode="dn1"/>         </schema>

        <dataNode name="dn1" dataHost="localhost1" database="db1" />         <dataNode name="dn2" dataHost="localhost1" database="db2" />         <dataNode name="dn3" dataHost="localhost1" database="db3" />         <dataNode name="dn4" dataHost="localhost1" database="db4" />         <dataNode name="dn5" dataHost="localhost1" database="db5" />

        <dataHost name="localhost1" maxCon="1000" minCon="20" balance="0" writeType="0" dbType="mysql" dbDriver="native">                 <heartbeat>select user()</heartbeat>                 <writeHost host="hostM1" url="127.0.0.1:3366" user="root" password="123456">                 </writeHost>         </dataHost> </mycat:schema>

3、mycat对应sequence_db_conf.properties增加相应设置； 4、mycat的对应mycat_sequence增加对应记录。 5、链接mycat，测试结果如下： 127.0.0.1/root:[TESTDB> insert into tt2(nm) values (99); Query OK, 1 row affected (0.14 sec)

127.0.0.1/root:[TESTDB> select last_insert_id(); +------------------+ | LAST_INSERT_ID() | +------------------+ |              101 | +------------------+ 1 row in set (0.01 sec)

127.0.0.1/root:[TESTDB> insert into tt2(nm) values (99); Query OK, 1 row affected (0.00 sec)

127.0.0.1/root:[TESTDB> select last_insert_id(); +------------------+ | LAST_INSERT_ID() | +------------------+ |              102 | +------------------+ 1 row in set (0.00 sec)

127.0.0.1/root:[TESTDB> insert into tt2(nm) values (99); Query OK, 1 row affected (0.00 sec)

127.0.0.1/root:[TESTDB> select last_insert_id(); +------------------+ | LAST_INSERT_ID() | +------------------+ |              103 | +------------------+ 1 row in set (0.00 sec)

127.0.0.1/root:[TESTDB> insert into tt2(nm) values (99); Query OK, 1 row affected (0.01 sec)

127.0.0.1/root:[TESTDB> select last_insert_id(); +------------------+ | LAST_INSERT_ID() | +------------------+ |              104 | +------------------+ 1 row in set (0.00 sec)

127.0.0.1/root:[TESTDB> insert into tt2(nm) values (99); Query OK, 1 row affected (0.00 sec)

127.0.0.1/root:[TESTDB> select last_insert_id(); +------------------+ | LAST_INSERT_ID() | +------------------+ |              105 | +------------------+ 1 row in set (0.00 sec)

127.0.0.1/root:[TESTDB> insert into tt2(nm) values (99); Query OK, 1 row affected (0.00 sec)

127.0.0.1/root:[TESTDB> select last_insert_id(); +------------------+ | LAST_INSERT_ID() | +------------------+ |              106 | +------------------+ 1 row in set (0.00 sec)