mycat 离散分片 -> 程序指定分区的分片

1。程序指定分区的分片

此规则是在运行阶段有应用自主决定路由到那个分片。

此方法为直接依据字符子串（必须是数字）计算分区号（由应用传递參数。显式指定分区号）。

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2，加入配置文件

在function.xml里面进行配置：

        <function name="sharding-by-substring-040302" class="org.opencloudb.route.function.PartitionDirectBySubString">
                <property name="startIndex">0</property>
                <property name="size">1</property>
                <property name="partitionCount">8</property>
                <property name="defaultPartition">0</property>
        </function>

    比如id=0-100000020在此配置中代表依据id中从startIndex=0，開始，截取siz=1位数字即0，0就是获取的分区，假设没传默认分配到defaultPartition

        <tableRule name="tr-sharding-substr-mc040302">
                 <rule>
                         <columns>CODE</columns>
                          <algorithm>sharding-by-substring-040302</algorithm>
                </rule>
        </tableRule>

在schema.xml里面进行配置：

    <table name="ORDER040302" primaryKey="ID" dataNode="dn21,dn22" rule="tr-sharding-substr-mc040302"/>

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3，建表而且录入数据

    CREATE TABLE ORDER040302(ID INT NOT NULL AUTO_INCREMENT PRIMARY KEY,CODE VARCHAR(64),SN VARCHAR(64),CREATE_TIME DATETIME);
    mysql> CREATE TABLE ORDER040302(ID INT NOT NULL AUTO_INCREMENT PRIMARY KEY,CODE VARCHAR(64),SN VARCHAR(64),CREATE_TIME DATETIME);
    Query OK, 0 rows affected (0.05 sec)

    mysql>
    INSERT INTO ORDER040302(ID,CODE,SN,CREATE_TIME) VALUES(1,'0-10000020','beijing_03-10000020',NOW());
    INSERT INTO ORDER040302(ID,CODE,SN,CREATE_TIME) VALUES(2,'1-10000020','shanghai_10-10000020',NOW());
    mysql> explain INSERT INTO ORDER040302(ID,CODE,SN,CREATE_TIME) VALUES(1,'0-10000020','beijing_03-10000020',NOW());
    +-----------+----------------------------------------------------------------------------------------------------+
    | DATA_NODE | SQL                                                                                                |
    +-----------+----------------------------------------------------------------------------------------------------+
    | dn21      | INSERT INTO ORDER040302(ID,CODE,SN,CREATE_TIME) VALUES(1,'0-10000020','beijing_03-10000020',NOW()) |
    +-----------+----------------------------------------------------------------------------------------------------+
    1 row in set (0.00 sec)

    mysql>
    mysql> INSERT INTO ORDER040302(ID,CODE,SN,CREATE_TIME) VALUES(1,'0-10000020','beijing_03-10000020',NOW());
    Query OK, 1 row affected (0.01 sec)

    mysql>
    mysql> explain INSERT INTO ORDER040302(ID,CODE,SN,CREATE_TIME) VALUES(2,'1-10000020','shanghai_10-10000020',NOW());
    +-----------+-----------------------------------------------------------------------------------------------------+
    | DATA_NODE | SQL                                                                                                 |
    +-----------+-----------------------------------------------------------------------------------------------------+
    | dn22      | INSERT INTO ORDER040302(ID,CODE,SN,CREATE_TIME) VALUES(2,'1-10000020','shanghai_10-10000020',NOW()) |
    +-----------+-----------------------------------------------------------------------------------------------------+
    1 row in set (0.00 sec)

    mysql> INSERT INTO ORDER040302(ID,CODE,SN,CREATE_TIME) VALUES(2,'1-10000020','shanghai_10-10000020',NOW());
    Query OK, 1 row affected (0.00 sec)

    mysql> 

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4，对insert操作流程进行分析，參考mycat.log对路由过程做完整的分析

查看后台mycat.log分析例如以下：

開始获取连接：
    02/13 00:40:18.173  DEBUG [$_NIOREACTOR-1-RW] (ServerQueryHandler.java:56) -ServerConnection [id=1, schema=TESTDB, host=127.0.0.1, user=test,txIsolation=3, autocommit=true, schema=TESTDB]INSERT INTO ORDER040302(ID,CODE,SN,CREATE_TIME) VALUES(2,'1-10000020','shanghai_10-10000020',NOW())

開始路由匹配：
    02/13 00:40:18.175  DEBUG [$_NIOREACTOR-1-RW] (NonBlockingSession.java:113) -ServerConnection [id=1, schema=TESTDB, host=127.0.0.1, user=test,txIsolation=3, autocommit=true, schema=TESTDB]INSERT INTO ORDER040302(ID,CODE,SN,CREATE_TIME) VALUES(2,'1-10000020','shanghai_10-10000020',NOW()), route={
       1 -> dn22{INSERT INTO ORDER040302(ID,CODE,SN,CREATE_TIME) VALUES(2,'1-10000020','shanghai_10-10000020',NOW())}

匹配好路由后，直接往相应的dn21节点開始运行insert数据录入操作：
    02/13 00:40:18.180  DEBUG [$_NIOREACTOR-1-RW] (NonBlockingSession.java:229) -release connection MySQLConnection [id=17, lastTime=1455295218162, user=root, schema=db3, old shema=db3, borrowed=true, fromSlaveDB=false, threadId=199, charset=latin1, txIsolation=3, autocommit=true, attachment=dn22{INSERT INTO ORDER040302(ID,CODE,SN,CREATE_TIME) VALUES(2,'1-10000020','shanghai_10-10000020',NOW())}, respHandler=SingleNodeHandler [node=dn22{INSERT INTO ORDER040302(ID,CODE,SN,CREATE_TIME) VALUES(2,'1-10000020','shanghai_10-10000020',NOW())}, packetId=0], host=10.254.1.11, port=3327, statusSync=null, writeQueue=0, modifiedSQLExecuted=true]

连接释放：
    02/13 00:40:18.180  DEBUG [$_NIOREACTOR-1-RW] (PhysicalDatasource.java:403) -release channel MySQLConnection [id=17, lastTime=1455295218162, user=root, schema=db3, old shema=db3, borrowed=true, fromSlaveDB=false, threadId=199, charset=latin1, txIsolation=3, autocommit=true, attachment=null, respHandler=null, host=10.254.1.11, port=3327, statusSync=null, writeQueue=0, modifiedSQLExecuted=false]
    02/13 00:40:24.390  DEBUG [Timer1] (SQLJob.java:85) -con query s

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5，运行简单的查询，假设指定分片字段ID字段，则走分片查询单个分片节点

mycat命令台显示结果：

    mysql> explain select * from ORDER040302 t1 where CODE= '0-10000020';
    +-----------+------------------------------------------------------------------+
    | DATA_NODE | SQL                                                              |
    +-----------+------------------------------------------------------------------+
    | dn21      | SELECT * FROM ORDER040302 t1 WHERE CODE = '0-10000020' LIMIT 100 |
    +-----------+------------------------------------------------------------------+
    1 row in set (0.00 sec)

    mysql> select * from ORDER040302 t1 where CODE= '0-10000020';
    +----+------------+---------------------+---------------------+
    | ID | CODE       | SN                  | CREATE_TIME         |
    +----+------------+---------------------+---------------------+
    |  1 | 0-10000020 | beijing_03-10000020 | 2016-02-13 00:40:27 |
    +----+------------+---------------------+---------------------+
    1 row in set (0.01 sec)

    mysql>

查看后台mycat日志信息：

    02/13 00:44:46.717  DEBUG [$_NIOREACTOR-1-RW] (ServerQueryHandler.java:56) -ServerConnection [id=1, schema=TESTDB, host=127.0.0.1, user=test,txIsolation=3, autocommit=true, schema=TESTDB]explain select * from ORDER040302 t1 where CODE= '0-10000020'
    02/13 00:44:46.718  DEBUG [$_NIOREACTOR-1-RW] (EnchachePool.java:76) -SQLRouteCache  miss cache ,key:TESTDB select * from ORDER040302 t1 where CODE= '0-10000020'
    02/13 00:44:46.719  DEBUG [$_NIOREACTOR-1-RW] (EnchachePool.java:59) -SQLRouteCache add cache ,key:TESTDB select * from ORDER040302 t1 where CODE= '0-10000020' value:select * from ORDER040302 t1 where CODE= '0-10000020', route={
       1 -> dn21{SELECT *
    FROM ORDER040302 t1
    WHERE CODE = '0-10000020'
    LIMIT 100}
    }

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6。假设分片字段范围的查询，则走全部节点去检索。哪怕仅仅有一条数据在一个分片上。route路由也是走全部的分片进行检索查询

    mysql> explain select * from ORDER040302 t1 where CODE likt '0-1%';
    +-----------+---------------------------------------------------+
    | DATA_NODE | SQL                                               |
    +-----------+---------------------------------------------------+
    | dn21      | SELECT * FROM ORDER040302 t1 WHERE CODE LIMIT 100 |
    | dn22      | SELECT * FROM ORDER040302 t1 WHERE CODE LIMIT 100 |
    +-----------+---------------------------------------------------+
    2 rows in set (0.00 sec)

    mysql> 

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7，假设不走分片字段的查询。即使是单个数据。也要route路由全部的分片，走全部的分片进行查询

    mysql> explain select * from ORDER040302 t1 where SN='beijing_03-10000020';
    +-----------+-------------------------------------------------------------------------+
    | DATA_NODE | SQL                                                                     |
    +-----------+-------------------------------------------------------------------------+
    | dn21      | SELECT * FROM ORDER040302 t1 WHERE SN = 'beijing_03-10000020' LIMIT 100 |
    | dn22      | SELECT * FROM ORDER040302 t1 WHERE SN = 'beijing_03-10000020' LIMIT 100 |
    +-----------+-------------------------------------------------------------------------+
    2 rows in set (0.00 sec)

    mysql>