配置单元中有两个属性与skew join相关。

<property>
    <name>hive.skewjoin.mapjoin.map.tasks</name>
    <value>10000</value>
    <description>
        Determine the number of map task used in the follow up map join job for a skew join.
        It should be used together with hive.skewjoin.mapjoin.min.split to perform a fine grained control.
    </description>
</property>
<property>
    <name>hive.skewjoin.mapjoin.min.split</name>
    <value>33554432</value>
    <description>
        Determine the number of map task at most used in the follow up map join job for a skew join by specifying
        the minimum split size. It should be used together with hive.skewjoin.mapjoin.map.tasks to perform a fine grained control.
    </description>
</property>

但我还是不明白这两者之间到底是什么关系 hive.skewjoin.mapjoin.map.tasks 定义Map任务数和 hive.skewjoin.mapjoin.min.split 最后还定义了map任务的数量。