分片（水平拆分）

4.全局表

业务使用场景：
如果你的业务中有些数据类似于数据字典，比如配置文件的配置，
常用业务的配置或者数据量不大很少变动的表，这些表往往不是特别大，
而且大部分的业务场景都会用到，那么这种表适合于Mycat全局表，无须对数据进行切分，
要在所有的分片上保存一份数据即可，Mycat 在Join操作中，业务表与全局表进行Join聚合会优先选择相同分片内的全局表join，
避免跨库Join，在进行数据插入操作时，mycat将把数据分发到全局表对应的所有分片执行，在进行数据读取时候将会随机获取一个节点读取数据。

cd /data/mycat/conf
cp schema.xml schema.xml.intfile

vi schema.xml
<?xml version="1.0"?>
<!DOCTYPE mycat:schema SYSTEM "schema.dtd">
<mycat:schema xmlns:mycat="http://io.mycat/">
<schema name="TESTDB" checkSQLschema="false" sqlMaxLimit="100" dataNode="sh1">
        <table name="t_area" dataNode="sh1,sh2" primaryKey="id"  type="global" />
</schema>
    <dataNode name="sh1" dataHost="oldguo1" database= "taobao" />
    <dataNode name="sh2" dataHost="oldguo2" database= "taobao" />
    <dataHost name="oldguo1" maxCon="1000" minCon="10" balance="1"  writeType="0" dbType="mysql"  dbDriver="native" switchType="1">
        <heartbeat>select user()</heartbeat>
    <writeHost host="db1" url="192.168.31.205:3307" user="root" password="123">
            <readHost host="db2" url="192.168.31.205:3309" user="root" password="123" />
    </writeHost>
    <writeHost host="db3" url="192.168.31.206:3307" user="root" password="123">
            <readHost host="db4" url="192.168.31.206:3309" user="root" password="123" />
    </writeHost>
    </dataHost>
    <dataHost name="oldguo2" maxCon="1000" minCon="10" balance="1"  writeType="0" dbType="mysql"  dbDriver="native" switchType="1">
        <heartbeat>select user()</heartbeat>
    <writeHost host="db1" url="192.168.31.205:3308" user="root" password="123">
            <readHost host="db2" url="192.168.31.205:3310" user="root" password="123" />
    </writeHost>
    <writeHost host="db3" url="192.168.31.206:3308" user="root" password="123">
            <readHost host="db4" url="192.168.31.206:3310" user="root" password="123" />
    </writeHost>
    </dataHost>
</mycat:schema>

准备数据

mysql -S /data/3307/mysql.sock -e "use taobao;create table t_area (id int not null primary key auto_increment,name varchar(20) not null);"
mysql -S /data/3308/mysql.sock -e "use taobao;create table t_area (id int not null primary key auto_increment,name varchar(20) not null);"

mycat restart
mysql -uroot -p123456 -h127.0.0.1 -P8066

use TESTDB
insert into t_area(id,name) values(1,'a');
insert into t_area(id,name) values(2,'b');
insert into t_area(id,name) values(3,'c');
insert into t_area(id,name) values(4,'d');

检查

mysql -S /data/3307/mysql.sock -e "use taobao;select * from t_area;"
+----+------+
| id | name |
+----+------+
|  1 | a    |
|  2 | b    |
|  3 | c    |
|  4 | d    |
+----+------+

mysql -S /data/3308/mysql.sock -e "use taobao;select * from t_area;"
+----+------+
| id | name |
+----+------+
|  1 | a    |
|  2 | b    |
|  3 | c    |
|  4 | d    |
+----+------+