Spark Dataframe验证镶木地板写入的列名(标量) [英] Spark Dataframe validating column names for parquet writes (scala)

问题描述

我正在使用从JSON事件流转换而来的数据帧处理事件，这些数据最终以Parquet格式写出.

I'm processing events using Dataframes converted from a stream of JSON events which eventually gets written out as as Parquet format.

但是，某些JSON事件在键中包含空格，我想在将其转换为Parquet之前记录并过滤/删除数据框中的此类事件，因为，; {}()\ n \ t =被认为是特殊的如以下 [1] 中所列的Parquet模式(CatalystSchemaConverter)中的字符，因此不应在列名称中使用这些字符.

However, some of the JSON events contains spaces in the keys which I want to log and filter/drop such events from the data frame before converting it to Parquet because ,;{}()\n\t= are considered special characters in Parquet schema (CatalystSchemaConverter) as listed in [1] below and thus should not be allowed in the column names.

如何在Dataframe中对列名称进行此类验证，并完全删除此类事件，而又不会错失Spark Streaming作业.

How can I do such validations in Dataframe on the column names and drop such an event altogether without erroring out the Spark Streaming job.

[1] Spark的CatalystSchemaConverter

[1] Spark's CatalystSchemaConverter

def checkFieldName(name: String): Unit = {
    // ,;{}()\n\t= and space are special characters in Parquet schema
    checkConversionRequirement(
      !name.matches(".*[ ,;{}()\n\t=].*"),
      s"""Attribute name "$name" contains invalid character(s) among " ,;{}()\\n\\t=".
         |Please use alias to rename it.
       """.stripMargin.split("\n").mkString(" ").trim)
  }

推荐答案

对于在 pyspark 中遇到此问题的每个人:重命名列后，这甚至都发生在我身上.在一些迭代之后，我可以使它工作的一种方法是:

For everyone experiencing this in pyspark: this even happened to me after renaming the columns. One way I could get this to work after some iterations is this:

file = "/opt/myfile.parquet"
df = spark.read.parquet(file)
for c in df.columns:
    df = df.withColumnRenamed(c, c.replace(" ", ""))

df = spark.read.schema(df.schema).parquet(file)

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