猪中的组串联等价物?

问题描述

试图在 Pig 上完成这项工作.(寻找相当于 MySQL 的 group_concat())

Trying to get this done on Pig. (Looking for the group_concat() equivalent of MySQL)

例如，在我的表中，我有这个:(3fields- userid, clickcount,pagenumber)

In my table, for example, I have this: (3fields- userid, clickcount,pagenumber)

155 | 2 | 12
155 | 3 | 133
155 | 1 | 144
156 | 6 | 1
156 | 7 | 5

所需的输出是:

155| 2,3,1 | 12,133,144

156| 6,7 | 1,5

我怎样才能在 PIG 上实现这一点?

How can I achieve this on PIG?

推荐答案

grouped = GROUP table BY userid;
   X = FOREACH grouped GENERATE group as userid, 
                                table.clickcount as clicksbag, 
                                table.pagenumber as pagenumberbag;

现在 X 将是:

{(155,{(2),(3),(1)},{(12),(133),(144)},
 (156,{(6),(7)},{(1),(5)}}

现在您需要使用 内置 UDF BagToTuple:

output = FOREACH X GENERATE userid, 
                            BagToTuple(clickbag) as clickcounts, 
                            BagToTuple(pagenumberbag) as pagenumbers;

output 现在应该包含您想要的内容.您也可以将输出步骤合并到合并步骤中:

output should now contain what you want. You can merge the output step into the merge step as well:

    output = FOREACH grouped GENERATE group as userid, 
                     BagToTuple(table.clickcount) as clickcounts, 
                     BagToTuple(table.pagenumber) as pagenumbers;

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