srowen commented on a change in pull request #23830: Decrease processing
overhead on DataFrameReader CSV calls with specif…
URL: https://github.com/apache/spark/pull/23830#discussion_r257853015
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File path: sql/core/src/main/scala/org/apache/spark/sql/DataFrameReader.scala
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@@ -508,7 +508,9 @@ 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)
+ filteredLines.take(1).headOption else None
Review comment:
This indent is off. I might just add the braces and newline for clarity.
Please see https://spark.apache.org/contributing.html ; this one probably
needs a JIRA and other modifications.
But more to the point this changes the logic of `linesWithoutHeader`. This
seems to skip handling the header too.
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