HyukjinKwon commented on a change in pull request #23830:
[SPARK-26935][SQL]Skip DataFrameReader's CSV first line scan when not used
URL: https://github.com/apache/spark/pull/23830#discussion_r258362101
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File path: sql/core/src/main/scala/org/apache/spark/sql/DataFrameReader.scala
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@@ -508,7 +508,12 @@ class DataFrameReader private[sql](sparkSession:
SparkSession) extends Logging {
sparkSession.sessionState.conf.sessionLocalTimeZone)
val filteredLines: Dataset[String] =
CSVUtils.filterCommentAndEmpty(csvDataset, parsedOptions)
- val maybeFirstLine: Option[String] = filteredLines.take(1).headOption
+ val maybeFirstLine: Option[String] =
+ if (userSpecifiedSchema.isEmpty || parsedOptions.headerFlag) {
Review comment:
not a big deal but I think you can use `isDefined` instead of `isEmpty`.
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