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MyCat分库分表的案例分析

发布时间：2021-12-30 04:03:58 所属栏目：MySql教程 来源：互联网
导读：这篇文章主要为大家展示了MyCat分库分表的示例分析，内容简而易懂，条理清晰，希望能够帮助大家解决疑惑，下面让小编带领大家一起研究并学习一下MyCat分库分表的示例分析这篇文章吧。 一、当前分片信息配置 schema.xml ?xml version=1.0? !DOCTYPE mycat:sc
这篇文章主要为大家展示了“MyCat分库分表的示例分析”，内容简而易懂，条理清晰，希望能够帮助大家解决疑惑，下面让小编带领大家一起研究并学习一下“MyCat分库分表的示例分析”这篇文章吧。
 
一、当前分片信息配置
 
schema.xml
 
<?xml version="1.0"?>
<!DOCTYPE mycat:schema SYSTEM "schema.dtd">
<mycat:schema xmlns:mycat="http://io.mycat/">
        <schema name="mycatdb" checkSQLschema="false" sqlMaxLimit="100">
           <table name="user04" dataNode="dn$1-3,dn$13-15,dn$25-27" rule="sharding-by-murmur-user04-id"></table>
        </schema>
<!-- <dataNode name="dn1$0-743" dataHost="localhost1" database="db$0-743"
/> -->
        <dataNode name="dn1" dataHost="node1" database="testdb01" />
        <dataNode name="dn2" dataHost="node1" database="testdb02" />
        <dataNode name="dn3" dataHost="node1" database="testdb03" />
       
        <dataNode name="dn13" dataHost="node2" database="testdb13" />
        <dataNode name="dn14" dataHost="node2" database="testdb14" />
        <dataNode name="dn15" dataHost="node2" database="testdb15" />
        
        <dataNode name="dn25" dataHost="node3" database="testdb25" />
        <dataNode name="dn26" dataHost="node3" database="testdb26" />
        <dataNode name="dn27" dataHost="node3" database="testdb27" />
        
        <!--<dataNode name="dn4" dataHost="sequoiadb1" database="SAMPLE" />
 <dataNode name="jdbc_dn1" dataHost="jdbchost" database="db1" />
<dataNode name="jdbc_dn2" dataHost="jdbchost" database="db2" />
<dataNode name="jdbc_dn3" dataHost="jdbchost" database="db3" /> -->
<dataHost name="node1" maxCon="1000" minCon="10" balance="1"
                          writeType="0" dbType="mysql" dbDriver="native" switchType="1"  slaveThreshold="100">
                <heartbeat>select user()</heartbeat>
                <!-- can have multi write hosts -->
                <writeHost host="192.168.8.31" url="192.168.8.31:3306" user="root"  password="mysql"></writeHost>
        </dataHost>
        <dataHost name="node2" maxCon="1000" minCon="10" balance="1"
                          writeType="0" dbType="mysql" dbDriver="native" switchType="1"  slaveThreshold="100">
                <heartbeat>select user()</heartbeat>
                <!-- can have multi write hosts -->
                <writeHost host="192.168.8.32" url="192.168.8.32:3306" user="root"  password="mysql"></writeHost>
        </dataHost>
        <dataHost name="node3" maxCon="1000" minCon="10" balance="1"
                          writeType="0" dbType="mysql" dbDriver="native" switchType="1"  slaveThreshold="100">
                <heartbeat>select user()</heartbeat>
                <!-- can have multi write hosts -->
                <writeHost host="192.168.8.33" url="192.168.8.33:3306" user="root"  password="mysql"></writeHost>
        </dataHost>
</mycat:schema>
rule.xml
 
<tableRule name="sharding-by-murmur-user04-id">
                <rule>
                        <columns>id</columns>
                        <algorithm>murmur-id</algorithm>
                </rule>
</tableRule>
<function name="murmur-id" class="io.mycat.route.function.PartitionByMurmurHash">
                <property name="seed">0</property><!-- 默认是 0 -->
                <property name="type">0</property><!-- 默认是 0, 表示 integer,非 0 表示 string-->
                <property name="count">9</property><!-- 要分片的数据库节点数量，必须指定，否则没法分片 -->
                <property name="virtualBucketTimes">160</property><!-- 一个实际的数据库节点被映射为这么多虚拟节点，默认是 160 倍，也就是虚拟节点数是物理节点数
的 160 倍 -->        
</function>
当前user04进行hash分区，共9个分片，存放在9个物理库。
 
二、数据查看
 
node1
 
mysql> select * from testdb01.user04;
+----+--------+
| id | name   |
+----+--------+
|  8 | steven |
| 14 | steven |
| 16 | steven |
| 17 | steven |
| 34 | steven |
| 49 | steven |
+----+--------+
6 rows in set (0.00 sec)
mysql> select * from testdb02.user04;
+----+--------+
| id | name   |
+----+--------+
|  9 | steven |
| 10 | steven |
| 44 | steven |
| 45 | steven |
| 46 | steven |
| 48 | steven |
+----+--------+
6 rows in set (0.06 sec)
mysql> select * from testdb03.user04;
+----+--------+
| id | name   |
+----+--------+
| 11 | steven |
| 24 | steven |
| 33 | steven |
| 35 | steven |
| 40 | steven |
+----+--------+
5 rows in set (0.07 sec)
node2
 
mysql> select * from testdb13.user04;
+----+--------+
| id | name   |
+----+--------+
| 20 | steven |
| 25 | steven |
| 38 | steven |
| 39 | steven |
+----+--------+
4 rows in set (0.07 sec)
mysql> select * from testdb14.user04;
+----+--------+
| id | name   |
+----+--------+
|  1 | steven |
| 41 | steven |
| 50 | steven |
+----+--------+
3 rows in set (0.03 sec)
mysql> select * from testdb15.user04;
+----+--------+
| id | name   |
+----+--------+
| 12 | steven |
| 18 | steven |
| 32 | steven |
| 36 | steven |
+----+--------+
4 rows in set (0.12 sec)
node3
 
mysql> select * from testdb25.user04;
+----+--------+
| id | name   |
+----+--------+
|  6 | steven |
| 13 | steven |
| 19 | steven |
| 23 | steven |
| 27 | steven |
| 28 | steven |
| 29 | steven |
| 31 | steven |
| 37 | steven |
+----+--------+
9 rows in set (0.05 sec)
mysql> select * from testdb26.user04;
+----+--------+
| id | name   |
+----+--------+
|  4 | steven |
|  5 | steven |
| 15 | steven |
| 22 | steven |
| 42 | steven |
+----+--------+
5 rows in set (0.01 sec)
mysql> select * from testdb27.user04;
+----+--------+
| id | name   |
+----+--------+
|  2 | steven |
|  3 | steven |
|  7 | steven |
| 21 | steven |
| 26 | steven |
| 30 | steven |
| 43 | steven |
| 47 | steven |
+----+--------+
8 rows in set (0.06 sec)
下面增加9个分片，重新进行配置
 
三、配置schema.xml，rule.xml
 
复制schema.xml、rule.xml并重命名为newSchema.xml、newRule.xml放于conf目录下，修改newSchema.xml和newRule.xml配置文件为扩容后的mycat配置参数(表的节点数、数据源、路由规则）
 
newSchema.xml
 
<?xml version="1.0"?>
<!DOCTYPE mycat:schema SYSTEM "schema.dtd">
<mycat:schema xmlns:mycat="http://io.mycat/">
        <schema name="mycatdb" checkSQLschema="false" sqlMaxLimit="100">
           <table name="user04" dataNode="dn$1-6,dn$13-18,dn$25-30" rule="sharding-by-murmur-user04-id"></table>
        </schema>
<!-- <dataNode name="dn1$0-743" dataHost="localhost1" database="db$0-743"
/> -->
        <dataNode name="dn1" dataHost="node1" database="testdb01" />
        <dataNode name="dn2" dataHost="node1" database="testdb02" />
        <dataNode name="dn3" dataHost="node1" database="testdb03" />
        <dataNode name="dn4" dataHost="node1" database="testdb04" />
        <dataNode name="dn5" dataHost="node1" database="testdb05" />
        <dataNode name="dn6" dataHost="node1" database="testdb06" />
        
        <dataNode name="dn13" dataHost="node2" database="testdb13" />
        <dataNode name="dn14" dataHost="node2" database="testdb14" />
        <dataNode name="dn15" dataHost="node2" database="testdb15" />
        <dataNode name="dn16" dataHost="node2" database="testdb16" />
        <dataNode name="dn17" dataHost="node2" database="testdb17" />
        <dataNode name="dn18" dataHost="node2" database="testdb18" />
        <dataNode name="dn25" dataHost="node3" database="testdb25" />
        <dataNode name="dn26" dataHost="node3" database="testdb26" />
        <dataNode name="dn27" dataHost="node3" database="testdb27" />
        <dataNode name="dn28" dataHost="node3" database="testdb28" />
        <dataNode name="dn29" dataHost="node3" database="testdb29" />
        <dataNode name="dn30" dataHost="node3" database="testdb30" />
        <!--<dataNode name="dn4" dataHost="sequoiadb1" database="SAMPLE" />
 <dataNode name="jdbc_dn1" dataHost="jdbchost" database="db1" />
<dataNode name="jdbc_dn2" dataHost="jdbchost" database="db2" />
<dataNode name="jdbc_dn3" dataHost="jdbchost" database="db3" /> -->
<dataHost name="node1" maxCon="1000" minCon="10" balance="1"
                          writeType="0" dbType="mysql" dbDriver="native" switchType="1"  slaveThreshold="100">
                <heartbeat>select user()</heartbeat>
                <!-- can have multi write hosts -->
                <writeHost host="192.168.8.31" url="192.168.8.31:3306" user="root"  password="mysql"></writeHost>
        </dataHost>
        <dataHost name="node2" maxCon="1000" minCon="10" balance="1"
                          writeType="0" dbType="mysql" dbDriver="native" switchType="1"  slaveThreshold="100">
                <heartbeat>select user()</heartbeat>
                <!-- can have multi write hosts -->
                <writeHost host="192.168.8.32" url="192.168.8.32:3306" user="root"  password="mysql"></writeHost>
        </dataHost>
        <dataHost name="node3" maxCon="1000" minCon="10" balance="1"
                          writeType="0" dbType="mysql" dbDriver="native" switchType="1"  slaveThreshold="100">
                <heartbeat>select user()</heartbeat>
                <!-- can have multi write hosts -->
                <writeHost host="192.168.8.33" url="192.168.8.33:3306" user="root"  password="mysql"></writeHost>
        </dataHost>
</mycat:schema>
newRule.xml
 
<tableRule name="sharding-by-murmur-user04-id">
                <rule>
                        <columns>id</columns>
                        <algorithm>murmur-id</algorithm>
                </rule>
</tableRule>
<function name="murmur-id" class="io.mycat.route.function.PartitionByMurmurHash">
                <property name="seed">0</property><!-- 默认是 0 -->
                <property name="type">0</property><!-- 默认是 0, 表示 integer,非 0 表示 string-->
                <property name="count">18</property><!-- 要分片的数据库节点数量，必须指定，否则没法分片 -->
                <property name="virtualBucketTimes">160</property><!-- 一个实际的数据库节点被映射为这么多虚拟节点，默认是 160 倍，也就是虚拟节点数是物理节点数
的 160 倍 -->        
</function>
将分片数量改为18
 
四、修改migrateTables.properties
 
#schema1=tb1,tb2,...
#schema2=all（写all或者不写将对此schema下拆分节点变化的拆分表全部进行重新路由）
#...
#sample
#TESTDB=travelrecord,company,goods
mycatdb=user04
五、重新分区
 
修改 bin 目录下的 dataMigrate.sh 脚本文件，
 
../bin/dataMigrate.sh
 
[root@mycat conf]# ../bin/dataMigrate.sh
"/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.161-2.b14.el7.x86_64/jre/bin/java" -DMYCAT_HOME="/usr/local/mycat" -classpath "/usr/local/mycat/conf:/usr/local/mycat/lib/classes:/usr/local/mycat/lib/asm-4.0.jar:/usr/local/mycat/lib/commons-collections-3.2.1.jar:/usr/local/mycat/lib/commons-lang-2.6.jar:/usr/local/mycat/lib/curator-client-2.11.0.jar:/usr/local/mycat/lib/curator-framework-2.11.0.jar:/usr/local/mycat/lib/curator-recipes-2.11.0.jar:/usr/local/mycat/lib/disruptor-3.3.4.jar:/usr/local/mycat/lib/dom4j-1.6.1.jar:/usr/local/mycat/lib/druid-1.0.26.jar:/usr/local/mycat/lib/ehcache-core-2.6.11.jar:/usr/local/mycat/lib/fastjson-1.2.12.jar:/usr/local/mycat/lib/guava-19.0.jar:/usr/local/mycat/lib/hamcrest-core-1.3.jar:/usr/local/mycat/lib/hamcrest-library-1.3.jar:/usr/local/mycat/lib/jline-0.9.94.jar:/usr/local/mycat/lib/joda-time-2.9.3.jar:/usr/local/mycat/lib/jsr305-2.0.3.jar:/usr/local/mycat/lib/kryo-2.10.jar:/usr/local/mycat/lib/leveldb-0.7.jar:/usr/local/mycat/lib/leveldb-api-0.7.jar:/usr/local/mycat/lib/log4j-1.2.17.jar:/usr/local/mycat/lib/log4j-1.2-api-2.5.jar:/usr/local/mycat/lib/log4j-api-2.5.jar:/usr/local/mycat/lib/log4j-core-2.5.jar:/usr/local/mycat/lib/log4j-slf4j-impl-2.5.jar:/usr/local/mycat/lib/mapdb-1.0.7.jar:/usr/local/mycat/lib/minlog-1.2.jar:/usr/local/mycat/lib/mongo-java-driver-2.11.4.jar:/usr/local/mycat/lib/Mycat-server-1.6.6.1-release.jar:/usr/local/mycat/lib/mysql-binlog-connector-java-0.16.1.jar:/usr/local/mycat/lib/mysql-connector-java-5.1.35.jar:/usr/local/mycat/lib/netty-3.7.0.Final.jar:/usr/local/mycat/lib/netty-buffer-4.1.9.Final.jar:/usr/local/mycat/lib/netty-common-4.1.9.Final.jar:/usr/local/mycat/lib/objenesis-1.2.jar:/usr/local/mycat/lib/reflectasm-1.03.jar:/usr/local/mycat/lib/sequoiadb-driver-1.12.jar:/usr/local/mycat/lib/slf4j-api-1.6.1.jar:/usr/local/mycat/lib/univocity-parsers-2.2.1.jar:/usr/local/mycat/lib/velocity-1.7.jar:/usr/local/mycat/lib/wrapper.jar:/usr/local/mycat/lib/zookeeper-3.4.6.jar" -server -Xms2G -Xmx2G -XX:MaxPermSize=64M -XX:+AggressiveOpts -XX:MaxDirectMemorySize=2G io.mycat.util.dataMigrator.DataMigrator -tempFileDir= -isAwaysUseMaster=true -mysqlBin= -cmdLength=110*1024 -charset=utf8 -deleteTempFileDir=true -threadCount= -delThreadCount= -queryPageSize=
OpenJDK 64-Bit Server VM warning: ignoring option MaxPermSize=64M; support was removed in 8.0
2018-11-23 17:25:57:664 [1]-> creating migrator schedule and temp files for migrate...
 +---------------------------------------------[mycatdb:user04] migrate info---------------------------------------------+
 |tableSize      = 50                                                                                                    |
 |migrate before = [dn1, dn2, dn3, dn13, dn14, dn15, dn25, dn26, dn27]                                                   |
 |migrate after  = [dn1, dn2, dn3, dn4, dn5, dn6, dn13, dn14, dn15, dn16, dn17, dn18, dn25, dn26, dn27, dn28, dn29, dn30]|
 |rule function  = PartitionByMurmurHash                                                                                 |
 +-----------------------------------------------------------------------------------------------------------------------+
 +----------------[mycatdb:user04] migrate schedule----------------+
 |dn13[4] -> [0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0]|
 |dn14[3] -> [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 2, 0]|
 |dn15[4] -> [0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0]|
 |dn1[6]  -> [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 1, 0, 0, 0, 1]|
 |dn25[9] -> [0, 0, 0, 0, 0, 0, 5, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 1]|
 |dn26[5] -> [0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 1, 0, 0, 1, 1, 0]|
 |dn27[8] -> [0, 0, 0, 0, 0, 0, 0, 0, 5, 0, 0, 0, 1, 1, 0, 0, 0, 0]|
 |dn2[6]  -> [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 1, 0, 0]|
 |dn3[5]  -> [0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0]|
 +-----------------------------------------------------------------+
2018-11-23 17:26:10:896 [2]-> start migrate data...
[mycatdb:user04] dn1->dn26 completed in 740ms
[mycatdb:user04] dn1->dn17 completed in 792ms
[mycatdb:user04] dn1->dn30 completed in 472ms
[mycatdb:user04] dn2->dn17 completed in 474ms
[mycatdb:user04] dn2->dn18 completed in 400ms
[mycatdb:user04] dn2->dn25 completed in 458ms
[mycatdb:user04] dn2->dn28 completed in 388ms
[mycatdb:user04] dn3->dn16 completed in 477ms
[mycatdb:user04] dn3->dn25 completed in 410ms
[mycatdb:user04] dn3->dn29 completed in 423ms
[mycatdb:user04] dn13->dn4 completed in 455ms
[mycatdb:user04] dn13->dn17 completed in 483ms
[mycatdb:user04] dn14->dn27 completed in 496ms
[mycatdb:user04] dn14->dn29 completed in 449ms
[mycatdb:user04] dn15->dn6 completed in 399ms
[mycatdb:user04] dn15->dn17 completed in 395ms
[mycatdb:user04] dn15->dn25 completed in 512ms
[mycatdb:user04] dn25->dn13 completed in 486ms
[mycatdb:user04] dn25->dn16 completed in 473ms
[mycatdb:user04] dn25->dn18 completed in 375ms
[mycatdb:user04] dn25->dn30 completed in 395ms
[mycatdb:user04] dn25->dn27 completed in 482ms
[mycatdb:user04] dn26->dn17 completed in 422ms
[mycatdb:user04] dn26->dn14 completed in 495ms
[mycatdb:user04] dn26->dn25 completed in 440ms
[mycatdb:user04] dn26->dn28 completed in 438ms
[mycatdb:user04] dn26->dn29 completed in 424ms
[mycatdb:user04] dn27->dn15 completed in 438ms
[mycatdb:user04] dn27->dn25 completed in 404ms
[mycatdb:user04] dn27->dn26 completed in 396ms
2018-11-23 17:26:18:106 [3]-> cleaning redundant data...
[mycatdb:user04] clean dataNode dn2 completed in 97ms
[mycatdb:user04] clean dataNode dn3 completed in 130ms
[mycatdb:user04] clean dataNode dn2 completed in 201ms
[mycatdb:user04] clean dataNode dn3 completed in 279ms
[mycatdb:user04] clean dataNode dn1 completed in 243ms
[mycatdb:user04] clean dataNode dn1 completed in 274ms
[mycatdb:user04] clean dataNode dn3 completed in 200ms
[mycatdb:user04] clean dataNode dn1 completed in 187ms
[mycatdb:user04] clean dataNode dn2 completed in 199ms
[mycatdb:user04] clean dataNode dn2 completed in 183ms
[mycatdb:user04] clean dataNode dn15 completed in 120ms
[mycatdb:user04] clean dataNode dn15 completed in 146ms
[mycatdb:user04] clean dataNode dn13 completed in 155ms
[mycatdb:user04] clean dataNode dn13 completed in 223ms
[mycatdb:user04] clean dataNode dn14 completed in 166ms
[mycatdb:user04] clean dataNode dn14 completed in 234ms
[mycatdb:user04] clean dataNode dn15 completed in 221ms
[mycatdb:user04] clean dataNode dn25 completed in 111ms
[mycatdb:user04] clean dataNode dn27 completed in 118ms
[mycatdb:user04] clean dataNode dn25 completed in 152ms
[mycatdb:user04] clean dataNode dn26 completed in 186ms
[mycatdb:user04] clean dataNode dn27 completed in 149ms
[mycatdb:user04] clean dataNode dn26 completed in 182ms
[mycatdb:user04] clean dataNode dn25 completed in 183ms
[mycatdb:user04] clean dataNode dn26 completed in 208ms
[mycatdb:user04] clean dataNode dn25 completed in 164ms
[mycatdb:user04] clean dataNode dn27 completed in 207ms
[mycatdb:user04] clean dataNode dn25 completed in 242ms
[mycatdb:user04] clean dataNode dn26 completed in 179ms
[mycatdb:user04] clean dataNode dn26 completed in 129ms
2018-11-23 17:26:21:423 [4]-> validating tables migrate result...
 +------migrate result-------+
 |[mycatdb:user04] -> success|
 +---------------------------+
2018-11-23 17:26:22:385 migrate data complete in 24736ms
六、重命名newSchema.xml和newRule.xml
 
扩容成功后，将newSchema.xml和newRule.xml重命名为schema.xml和rule.xml并替换掉原文件，重启mycat服务，整个扩容过程完成。
 
七、验证数据
 
node1
 
mysql> select * from testdb01.user04;
+----+--------+
| id | name   |
+----+--------+
| 16 | steven |
| 49 | steven |
+----+--------+
2 rows in set (0.01 sec)
mysql> select * from testdb02.user04;
+----+--------+
| id | name   |
+----+--------+
| 46 | steven |
| 48 | steven |
+----+--------+
2 rows in set (0.00 sec)
mysql> select * from testdb03.user04;
+----+--------+
| id | name   |
+----+--------+
| 24 | steven |
| 40 | steven |
+----+--------+
2 rows in set (0.00 sec)
mysql> select * from testdb04.user04;
+----+--------+
| id | name   |
+----+--------+
| 20 | steven |
| 25 | steven |
| 39 | steven |
+----+--------+
3 rows in set (0.00 sec)
mysql> select * from testdb05.user04;
Empty set (0.01 sec)
mysql> select * from testdb06.user04;
+----+--------+
| id | name   |
+----+--------+
| 32 | steven |
| 36 | steven |
+----+--------+
2 rows in set (0.00 sec)
node2
 
mysql> select * from testdb13.user04;
+----+--------+
| id | name   |
+----+--------+
|  6 | steven |
| 19 | steven |
| 23 | steven |
| 28 | steven |
| 29 | steven |
+----+--------+
5 rows in set (0.01 sec)
mysql> select * from testdb14.user04;
+----+--------+
| id | name   |
+----+--------+
|  5 | steven |
+----+--------+
1 row in set (0.00 sec)
mysql> select * from testdb15.user04;
+----+--------+
| id | name   |
+----+--------+
|  7 | steven |
| 26 | steven |
| 30 | steven |
| 43 | steven |
| 47 | steven |
+----+--------+
5 rows in set (0.01 sec)
mysql> select * from testdb16.user04;
+----+--------+
| id | name   |
+----+--------+
| 33 | steven |
| 37 | steven |
+----+--------+
2 rows in set (0.00 sec)
mysql> select * from testdb17.user04;
+----+--------+
| id | name   |
+----+--------+
| 10 | steven |
| 12 | steven |
| 14 | steven |
| 15 | steven |
| 34 | steven |
| 38 | steven |
+----+--------+
6 rows in set (0.01 sec)
mysql> select * from testdb18.user04;
+----+--------+
| id | name   |
+----+--------+
| 31 | steven |
| 45 | steven |
+----+--------+
2 rows in set (0.00 sec)
node3
 
mysql> select * from testdb25.user04;
+----+--------+
| id | name   |
+----+--------+
|  2 | steven |
| 18 | steven |
| 22 | steven |
| 35 | steven |
| 44 | steven |
+----+--------+
5 rows in set (0.01 sec)
mysql> select * from testdb26.user04;
+----+--------+
| id | name   |
+----+--------+
|  3 | steven |
| 17 | steven |
+----+--------+
2 rows in set (0.00 sec)
mysql> select * from testdb27.user04;
+----+--------+
| id | name   |
+----+--------+
| 21 | steven |
| 27 | steven |
| 41 | steven |
+----+--------+
3 rows in set (0.00 sec)
mysql> select * from testdb28.user04;
+----+--------+
| id | name   |
+----+--------+
|  9 | steven |
| 42 | steven |
+----+--------+
2 rows in set (0.00 sec)
mysql> select * from testdb29.user04;
+----+--------+
| id | name   |
+----+--------+
|  1 | steven |
|  4 | steven |
| 11 | steven |
| 50 | steven |
+----+--------+
4 rows in set (0.00 sec)
mysql> select * from testdb30.user04;
+----+--------+
| id | name   |
+----+--------+
|  8 | steven |
| 13 | steven |
+----+--------+
2 rows in set (0.00 sec)
可以看到user04分片由原来的9个分片变成了18个分片，验证完毕。
 
下面我们将缩减分片至9个分片
 
八、配置schema.xml，rule.xml
 
复制schema.xml、rule.xml并重命名为newSchema.xml、newRule.xml放于conf目录下，修改newSchema.xml和newRule.xml配置文件为缩容后的mycat配置参数(表的节点数、数据源、路由规则）
 
        <!--<dataNode name="dn4" dataHost="sequoiadb1" database="SAMPLE" />
 <dataNode name="jdbc_dn1" dataHost="jdbchost" database="db1" />
<dataNode name="jdbc_dn2" dataHost="jdbchost" database="db2" />
<dataNode name="jdbc_dn3" dataHost="jdbchost" database="db3" /> -->
<dataHost name="node1" maxCon="1000" minCon="10" balance="1"
                          writeType="0" dbType="mysql" dbDriver="native" switchType="1"  slaveThreshold="100">
                <heartbeat>select user()</heartbeat>
                <!-- can have multi write hosts -->
                <writeHost host="192.168.8.31" url="192.168.8.31:3306" user="root"  password="mysql"></writeHost>
        </dataHost>
        <dataHost name="node2" maxCon="1000" minCon="10" balance="1"
                          writeType="0" dbType="mysql" dbDriver="native" switchType="1"  slaveThreshold="100">
                <heartbeat>select user()</heartbeat>
                <!-- can have multi write hosts -->
                <writeHost host="192.168.8.32" url="192.168.8.32:3306" user="root"  password="mysql"></writeHost>
        </dataHost>
        <dataHost name="node3" maxCon="1000" minCon="10" balance="1"
                          writeType="0" dbType="mysql" dbDriver="native" switchType="1"  slaveThreshold="100">
                <heartbeat>select user()</heartbeat>
                <!-- can have multi write hosts -->
                <writeHost host="192.168.8.33" url="192.168.8.33:3306" user="root"  password="mysql"></writeHost>
        </dataHost>
</mycat:schema>
newRule.xml
 
<tableRule name="sharding-by-murmur-user04-id">
                <rule>
                        <columns>id</columns>
                        <algorithm>murmur-id</algorithm>
                </rule>
</tableRule>
<function name="murmur-id" class="io.mycat.route.function.PartitionByMurmurHash">
                <property name="seed">0</property><!-- 默认是 0 -->
                <property name="type">0</property><!-- 默认是 0, 表示 integer,非 0 表示 string-->
                <property name="count">9</property><!-- 要分片的数据库节点数量，必须指定，否则没法分片 -->
                <property name="virtualBucketTimes">160</property><!-- 一个实际的数据库节点被映射为这么多虚拟节点，默认是 160 倍，也就是虚拟节点数是物理节点数
的 160 倍 -->        
</function>
九、重新分区
 
 +------migrate result-------+
 |[mycatdb:user04] -> success|
 +---------------------------+
2018-11-23 17:47:18:102 migrate data complete in 16057ms
十、重命名newSchema.xml和newRule.xml
 
缩容成功后，将newSchema.xml和newRule.xml重命名为schema.xml和rule.xml并替换掉原文件，重启mycat服务，整个缩容过程完成。
 
十一、验证数据
 
node1
 
mysql> select * from testdb01.user04;
+----+--------+
| id | name   |
+----+--------+
|  8 | steven |
| 14 | steven |
| 16 | steven |
| 17 | steven |
| 34 | steven |
| 49 | steven |
+----+--------+
6 rows in set (0.00 sec)
mysql> select * from testdb02.user04;
+----+--------+
| id | name   |
+----+--------+
|  9 | steven |
| 10 | steven |
| 44 | steven |
| 45 | steven |
| 46 | steven |
| 48 | steven |
+----+--------+
6 rows in set (0.00 sec)
mysql> select * from testdb03.user04;
+----+--------+
| id | name   |
+----+--------+
| 11 | steven |
| 24 | steven |
| 33 | steven |
| 35 | steven |
| 40 | steven |
+----+--------+
5 rows in set (0.01 sec)
mysql> select * from testdb04.user04;
Empty set (0.00 sec)
mysql> select * from testdb05.user04;
Empty set (0.01 sec)
mysql> select * from testdb06.user04;
Empty set (0.00 sec)
node2
 
mysql> select * from testdb13.user04;
+----+--------+
| id | name   |
+----+--------+
| 20 | steven |
| 25 | steven |
| 38 | steven |
| 39 | steven |
+----+--------+
4 rows in set (0.00 sec)
mysql> select * from testdb14.user04;
+----+--------+
| id | name   |
+----+--------+
|  1 | steven |
| 41 | steven |
| 50 | steven |
+----+--------+
3 rows in set (0.00 sec)
mysql> select * from testdb15.user04;
+----+--------+
| id | name   |
+----+--------+
| 12 | steven |
| 18 | steven |
| 32 | steven |
| 36 | steven |
+----+--------+
4 rows in set (0.00 sec)
mysql> select * from testdb16.user04;
Empty set (0.00 sec)
mysql> select * from testdb17.user04;
Empty set (0.00 sec)
mysql> select * from testdb18.user04;
Empty set (0.00 sec)
node3
 
mysql> select * from testdb25.user04;
+----+--------+
| id | name   |
+----+--------+
|  6 | steven |
| 13 | steven |
| 19 | steven |
| 23 | steven |
| 27 | steven |
| 28 | steven |
| 29 | steven |
| 31 | steven |
| 37 | steven |
+----+--------+
9 rows in set (0.01 sec)
mysql> select * from testdb26.user04;
+----+--------+
| id | name   |
+----+--------+
|  4 | steven |
|  5 | steven |
| 15 | steven |
| 22 | steven |
| 42 | steven |
+----+--------+
5 rows in set (0.01 sec)
mysql> select * from testdb27.user04;
+----+--------+
| id | name   |
+----+--------+
|  2 | steven |
|  3 | steven |
|  7 | steven |
| 21 | steven |
| 26 | steven |
| 30 | steven |
| 43 | steven |
| 47 | steven |
+----+--------+
8 rows in set (0.01 sec)
mysql> select * from testdb28.user04;
Empty set (0.00 sec)
mysql> select * from testdb29.user04;
Empty set (0.00 sec)
mysql> select * from testdb30.user04;
Empty set (0.00 sec)
缩容之后，user04的所有数据变成了9个分片，其他分片没有存放数据，验证完毕。
 
遇到的问题：
 
由于测试环境之前用作一主两从测试环境，开启了gtid_mode，所以出现报错：
 
ERROR 1840 (HY000) at line 3 in file: '/usr/local/mycat/temp/mycatdb-user04/dn1(old)-dn17(new)/user04.sql': @@GLOBAL.GTID_PURGED can only be set when @@GLOBAL.GTID_EXECUTED is empty. -> mysql -h292.168.8.32 -P3306 -uroot -pmysql -Dtestdb17  -f --default-character-set=utf8 -e "source /usr/local/mycat/temp/mycatdb-user04/dn1(old)-dn17(new)/user04.sql"
 
解决方法：关闭gtid_mode
 
另外，扩容也可以采用停机方法，备份逻辑表所有数据，重新进行分片，然后再导入备份的数据，从而完成扩容的目的。
 
以上是“MyCat分库分表的示例分析”这篇文章的所有内容，感谢各位的阅读！

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