保存DataFrame时如何避免生成crc文件和SUCCESS文件? [英] How to avoid generating crc files and SUCCESS files while saving a DataFrame?

问题描述

我使用以下代码将 spark DataFrame 保存到 JSON 文件

I am using the following code to save a spark DataFrame to JSON file

unzipJSON.write.mode("append").json("/home/eranw/Workspace/JSON/output/unCompressedJson.json")

输出结果为:

part-r-00000-704b5725-15ea-4705-b347-285a4b0e7fd8
.part-r-00000-704b5725-15ea-4705-b347-285a4b0e7fd8.crc
part-r-00001-704b5725-15ea-4705-b347-285a4b0e7fd8
.part-r-00001-704b5725-15ea-4705-b347-285a4b0e7fd8.crc
_SUCCESS
._SUCCESS.crc

1. 如何生成单个 JSON 文件而不是每行一个文件?
2. 如何避免 *crc 文件?
3. 如何避免 SUCCESS 文件?

推荐答案

如果你想要单个文件，你需要在调用 write 之前对单个分区做一个coalesce，所以:

If you want a single file, you need to do a coalesce to a single partition before calling write, so:

unzipJSON.coalesce(1).write.mode("append").json("/home/eranw/Workspace/JSON/output/unCompressedJson.json")

就个人而言，我发现输出文件的数量取决于您在调用 write 之前拥有的分区数量这一点很烦人 - 特别是如果您使用 write 执行 writecode>partitionBy - 但据我所知，目前没有其他方法.

Personally, I find it rather annoying that the number of output files depend on number of partitions you have before calling write - especially if you do a write with a partitionBy - but as far as I know, there are currently no other way.

我不知道是否有一种方法可以禁用 .crc 文件 - 我不知道有一种方法 - 但是您可以通过在 Spark 上下文的 hadoop 配置中设置以下内容来禁用 _SUCCESS 文件.

I don't know if there is a way to disable the .crc files - I don't know of one - but you can disable the _SUCCESS file by setting the following on the hadoop configuration of the Spark context.

sc.hadoopConfiguration.set("mapreduce.fileoutputcommitter.marksuccessfuljobs", "false")

请注意，您可能还想通过以下方式禁用元数据文件的生成:

Note, that you may also want to disable generation of the metadata files with:

sc.hadoopConfiguration.set("parquet.enable.summary-metadata", "false")

显然，生成元数据文件需要一些时间(参见 这篇博文) 但实际上并不那么重要(根据 这个).就个人而言，我总是禁用它们，我没有遇到任何问题.

Apparently, generating the metadata files takes some time (see this blog post) but aren't actually that important (according to this). Personally, I always disable them and I have had no issues.

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