group by 和count distinctselect count(t.order_no) from (select order_no from order_snap group by order_no) t;原理 shuffle到一个reducer的数据太大
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297 序列化/反序列化二叉树1234567891011121314151617181920212223242526272829303132333435private static final String spliter = ","; private static final String NN
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