FAILED.NullPointerException在HIVE QUERY中为null。HIVE QUERY中的NullPointerException为空。

Question

以下是我正在使用的HIVE查询，我还使用了一个Ranking函数。我在我的本地机器上运行这个查询。

SELECT numeric_id, location, Rank(location), followers_count
FROM (
SELECT  numeric_id, location, followers_count
FROM twitter_data
DISTRIBUTE BY numeric_id, location
SORT BY numeric_id, location, followers_count desc
) a
WHERE Rank(location)<10;

我的Rank函数如下。

package org.apache.hadoop.hive.contrib.udaf.ex;

import org.apache.hadoop.hive.ql.exec.UDF;



public final class Rank extends UDF{
    private int  counter;
    private String last_key;
    public int evaluate(final String key){
      if ( !key.equalsIgnoreCase(this.last_key) ) {
         this.counter = 0;
         this.last_key = key;
      }
      return this.counter++;
    }
}

我创建了上述文件的Jar，然后在运行hive查询之前，做了以下步骤。我试着用runnable jar来做，也试着用简单的来创建。

ADD JAR /home/adminpc/Downloads/Project_input/Rank.jar;
CREATE TEMPORARY FUNCTION Rank AS 'org.apache.hadoop.hive.contrib.udaf.ex.Rank';

这是我执行Hive查询后的结果------。

hive> SELECT numeric_id, location, Rank(location), followers_count
    > FROM (
    > SELECT  numeric_id, location, followers_count
    > FROM twitter_data
    > DISTRIBUTE BY numeric_id, location
    > SORT BY numeric_id, location, followers_count desc
    > ) a
    > WHERE Rank(location)<1;
FAILED: NullPointerException null

Answer 1

你的UDF似乎并没有保护输入表中的空值，特别是：检查当位置为空时，会发生什么。