如何在Hive中生成所有n-gram

小编典典

如何在Hive中生成所有n-gram

sql

我想使用HiveQL创建一个n-gram列表。我的想法是使用带正则表达式和split函数的正则表达式-但这不起作用，但是：

select split('This is my sentence', '(\\S+) +(?=(\\S+))');

输入是表格的一列

|sentence                 |
|-------------------------|
|This is my sentence      |
|This is another sentence |

输出应该是：

["This is","is my","my sentence"]
["This is","is another","another sentence"]

Hive中有一个n-gram udf，但是该函数直接计算n-gram的频率-我想改为列出所有n-gram的列表。

在此先多谢！

阅读 200

2021-03-10

共1个答案

小编典典

这可能不是最佳的解决方案，但却是可行的解决方案。用定界符分割句子（在我的示例中是一个或多个空格或逗号），然后爆炸并合并以得到n-
gram，然后使用collect_set（如果需要唯一的n-gram）或n组合n-gram数组collect_list：

with src as 
(
select source_data.sentence, words.pos, words.word
  from
      (--Replace this subquery (source_data) with your table
       select stack (2,
                     'This is my sentence', 
                     'This is another sentence'
                     ) as sentence
      ) source_data 
        --split and explode words
        lateral view posexplode(split(sentence, '[ ,]+')) words as pos, word
)

select s1.sentence, collect_set(concat_ws(' ',s1.word, s2.word)) as ngrams 
      from src s1 
           inner join src s2 on s1.sentence=s2.sentence and s1.pos+1=s2.pos              
group by s1.sentence;

结果：

OK
This is another sentence        ["This is","is another","another sentence"]
This is my sentence             ["This is","is my","my sentence"]
Time taken: 67.832 seconds, Fetched: 2 row(s)

2021-03-10