title: Access unique key (writeJobUUID) in parquet filename when saving PySpark DataFrame
body: <p>I'm looking for a way to access the unique part(s) of the parquet filename when saving a Spark DataFrame as Parquet with PySpark.</p>
  
  <p>Just read in <a href="https://stackoverflow.com/questions/36107581/change-output-filename-prefix-for-dataframe-write">Change output filename prefix for DataFrame.write()</a> that changing the output filename prefix for DataFrame.write() is not possible, though I like to know if there is a way to access the values used in RecordWriter to build up the filename.</p>
  
  <p>I had a look at the <a href="https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetRelation.scala#L491-L515" rel="nofollow noreferrer">a source code</a>, and saw that it's configuration.get("spark.sql.sources.writeJobUUID"), does this property gets initialized earlier, and is it also accessible through PySpark?</p>
  
  <p>I'd like to use it for logging purposes, to match a specific Spark job to the parquet files written (so I can e.g. remove all output by a specific job in different output partitions).</p>