Question

我有一个Hive表，用于跟踪在一个进程的各个阶段中移动的对象的状态。该表如下所示：

hive> desc journeys;
object_id           string                                      
journey_statuses    array<string>

以下是记录的典型示例：

12345678    ["A","A","A","B","B","B","C","C","C","C","D"]

表中的记录是使用Hive 0.13的collect_list生成的，状态有一个订单（如果订单不重要，我会使用collect_set）。对于每个object_id，我想缩短旅程按照它们出现的顺序返回旅程状态。

我写了一个从stdin读取的快速Python脚本：

#!/usr/bin/env python
import sys
import itertools

for line in sys.stdin:
    inputList = eval(line.strip())
    readahead = iter(inputList)
    next(readahead)
    result = []
    for id, (a, b) in enumerate(itertools.izip(inputList, readahead)):
        if id == 0:
          result.append(a)
        if a != b:
          result.append(b)
    print result

我计划在Hive transform电话中使用此功能。它似乎在本地运行时有效：

$ echo '["A","A","A","B","B","B","C","C","C","C","D"]' | python abbreviate_list.py
['A', 'B', 'C', 'D']

但是，当我添加文件并尝试在Hive中执行时，会返回错误：

hive> add file abbreviateList.py;                                                                           
Added resource: abbreviateList.py

hive> select
    >   object_id,
    >   transform(journey_statuses) using 'python abbreviateList.py' as journey_statuses_abbreviated
    > from journeys;
NoViableAltException( ... wall of Java error messages ... )
FAILED: ParseException line 3:2 cannot recognize input near 'transform' '(' 'journey_statuses' in select expression

你能看出我做错了吗？

Answer 1

显然，您无法选择其他不在转换中的字段（在您的示例中为object_id）。这个其他的SO问题似乎间接地解决了这个问题：

How can select a column and do a TRANSFORM in Hive?

理论上，您可以修改Python以接受object_id作为输入参数，如果需要将其包含在输出中，则将其作为另一个输出字段的直通。

具有python转换功能的Hive：＆＃34;无法识别转换附近的输入＆＃39;＆＃34;错误

1 个答案: