[GitHub] [spark] HyukjinKwon commented on a change in pull request #27031: [SPARK-30373][SQL] Avoid unnecessary sort for ParquetUtils.splitFiles

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HyukjinKwon commented on a change in pull request #27031: [SPARK-30373][SQL] Avoid unnecessary sort for ParquetUtils.splitFiles
URL: https://github.com/apache/spark/pull/27031#discussion_r361915141
 
 

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 File path: sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetUtils.scala
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 @@ -112,15 +114,26 @@ object ParquetUtils {
       metadata: Seq[FileStatus],
       commonMetadata: Seq[FileStatus])
 
-  private def splitFiles(allFiles: Seq[FileStatus]): FileTypes = {
-    val leaves = allFiles.toArray.sortBy(_.getPath.toString)
 
 Review comment:
   It was actually @liancheng's advice (wow 5 years ago). Sorting it will gives you a deterministic result. Relying on the native listing order doesn't look a great idea. From a cursory look, HDFS's vs Java's `File.list` (by `RawLocalFileSystem`) behaviours look inconsistent as an example.
   
   In addition, sorting itself won't cause a lot of performance penalty given most of performance penalty comes from listing up files, and given that the number of files should be, really, really high which isn't a pretty common case.

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