Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/16481#discussion_r95299609
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/DataSource.scala
---
@@ -413,17 +413,22 @@ case class DataSource(
relation
}
- /** Writes the given [[DataFrame]] out to this [[DataSource]]. */
+ /**
+ * Writes the given [[DataFrame]] out to this [[DataSource]].
+ *
+ * @param isForWriteOnly Whether to just write the data without
returning a [[BaseRelation]].
+ */
def write(
mode: SaveMode,
- data: DataFrame): BaseRelation = {
+ data: DataFrame,
+ isForWriteOnly: Boolean = false): Option[BaseRelation] = {
if
(data.schema.map(_.dataType).exists(_.isInstanceOf[CalendarIntervalType])) {
throw new AnalysisException("Cannot save interval data type into
external storage.")
}
providingClass.newInstance() match {
case dataSource: CreatableRelationProvider =>
- dataSource.createRelation(sparkSession.sqlContext, mode,
caseInsensitiveOptions, data)
+ Some(dataSource.createRelation(sparkSession.sqlContext, mode,
caseInsensitiveOptions, data))
--- End diff --
it would be really weird if `CreatableRelationProvider.createRelation` can
return a relation with different schema from the written `data`. Is it safe to
assume the schema won't change? cc @marmbrus @yhuai @liancheng
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