猪:位置数从对不对？

Question

我的猪剧本里有一个元组：

((,v1,fb,fql))

我知道我可以从左边选择元素，如$0 (空白)，$1 ("v1")等等，但是我可以从右边选择元素吗？元组将是不同的长度，但我总是想得到最后一个元素。

Answer 1

但是，您可以编写一个python来提取它：

# Make sure to include the appropriate ouputSchema
def getFromBack(TUPLE, pos):
    # gets elements from the back of TUPLE 
    # You can also do TUPLE[-pos], but this way it starts at 0 which is closer
    # to Pig
    return TUPLE[::-1][pos]

    # This works the same way as above, but may be faster
    # return TUPLE[-(pos + 1)]

并用于：

register 'myudf.py' using jython as pythonUDFs ;

B = FOREACH A GENERATE pythonUDFs.getFromBack(T, 0) ;