Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/16854#discussion_r104329474
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/DataFrameReader.scala ---
@@ -399,6 +395,56 @@ class DataFrameReader private[sql](sparkSession:
SparkSession) extends Logging {
}
/**
+ * Loads an `Dataset[String]` storing CSV rows and returns the result as
a `DataFrame`.
+ *
+ * If the schema is not specified using `schema` function and
`inferSchema` option is enabled,
+ * this function goes through the input once to determine the input
schema.
+ *
+ * If the schema is not specified using `schema` function and
`inferSchema` option is disabled,
+ * it determines the columns as string types and it reads only the first
line to determine the
+ * names and the number of fields.
+ *
+ * @param csvDataset input Dataset with one CSV row per record
+ * @since 2.2.0
+ */
+ def csv(csvDataset: Dataset[String]): DataFrame = {
+ val parsedOptions: CSVOptions = new CSVOptions(
+ extraOptions.toMap,
+ sparkSession.sessionState.conf.sessionLocalTimeZone)
+ val filteredLines = CSVUtils.filterCommentAndEmpty(csvDataset,
parsedOptions)
+ val maybeFirstLine = filteredLines.take(1).headOption
--- End diff --
why call `take(1)`?
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