在Google Cloud Dataflow中使用带有复杂PCollection类型的TextIO.Write [英] Using TextIO.Write with a complicated PCollection type in Google Cloud Dataflow

问题描述

我的PCollection看起来像这样：

I have a PCollection that looks like this:

PCollection<KV<KV<String, EventSession>, Long>> windowed_counts

我的目标是将其作为文本文件写出来。我想用
之类的东西：

My goal is to write this out as a text file. I thought to use something like:

windowed_counts.apply( TextIO.Write.to( "output" ));

但我很难正确设置Coders。这是我认为可行的：

but am having a hard time getting the Coders setup correctly. This is what I thought would work:

    KvCoder kvcoder = KvCoder.of(KvCoder.of(StringUtf8Coder.of(), AvroDeterministicCoder.of(EventSession.class) ), TextualLongCoder.of());
    TextIO.Write.Bound io = TextIO.Write.withCoder( kvcoder );
    windowed_counts.apply( io.to( "output" ));

其中TextualLongCoder是我自己的AtomicCoder子类，类似于TextualIntegerCoder。 EventSession类注释为使用AvroDeterministicCoder作为其默认编码器。

where TextualLongCoder is my own subclass of AtomicCoder, analogous to TextualIntegerCoder. The EventSession class is annotated to use AvroDeterministicCoder as it's default coder.

但有了这个，我得到包含非文本字符等的乱码输出。有人可以建议你如何将这个特定的PCollection写成文本吗？我确信这里有一些显而易见的东西......

But with this I get garbled output that includes non-textual character, etc. Can anybody advice on how you would write this particular PCollection out as text? I'm sure there's something obvious I'm missing here...

推荐答案

您是否尝试过创建转换后的转换？ PCollection KV< KV< String，EventSession> ;, Long> 到 PCollection of String s然后将其写入文本文件？

Did you try creating a transform that will convert a PCollection of KV<KV<String, EventSession>, Long> to a PCollection of Strings and then writing it into a text file?

我发现它是最灵活的方式满足我的需求

I found it to be most flexible way for my needs

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