在 Pig 中将多个地图组合在一起 [英] Combining Multiple Maps together in Pig

问题描述

我第一次使用猪.我已经得到了我想要的答案，但采用了奇怪的嵌套格式:

I am using pig for the first time. I've gotten to the point where I have exactly the answer I want, but in a weirdly nested format:

{(price,49),(manages,"1d74426f-2b0a-4777-ac1b-042268cab09c")}

我希望输出是一个单一的地图，没有任何包装:

I'd like the output to be a single map, without any wrapping:

[price#49, manages#"1d74426f-2b0a-4777-ac1b-042268cab09c"]

我已经设法使用 TOMAP 做到了这一点，但我不知道如何合并和扁平化它.

I've managed to use TOMAP to get this far, but I can't figure out how to merge and flatten it away.

{([price_specification#{"amount":49,"currency":"USD"}]),([manages#"newest-nodes/1d74426f-2b0a-4777-ac1b-042268cab09c"])}

我该怎么办?

推荐答案

遗憾的是，没有内置函数可以为您执行此操作.您必须编写自己的 UDF.幸运的是，这很简单.

Unfortunately, there are no built-in functions to do this for you. You'll have to write your own UDF. Fortunately, this is a simple one.

exec 方法将类似于:

public Map<String, Object> exec(Tuple input) {
    Map<String, Object> m = new HashMap<String, Object>();
    for (int i = 0; i < input.size(); i++)
        m.putAll((Map<String, Object>) input.get(i));

    return m;
}

UDF 可以将任意数量的映射作为参数.

The UDF could take any number of maps as arguments.

请注意，如果两个或多个映射共享一个密钥，则遇到的最后一个将是保留的，其他的将被覆盖.

Note that if two or more maps share a key, then the final one encountered will be the one that is kept and the others get overwritten.

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