Github user marmbrus commented on a diff in the pull request:
https://github.com/apache/spark/pull/12080#discussion_r58424444
--- Diff: sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala ---
@@ -449,6 +450,17 @@ class Dataset[T] private[sql](
def isLocal: Boolean = logicalPlan.isInstanceOf[LocalRelation]
/**
+ * Returns true if the underlying query will be executed continuously as
new data comes in.
+ * Methods that return bounded values, e.g. [[count()]], [[collect()]]
will throw
+ * an exception if a Dataset is streaming.
--- End diff --
How about?
```
Returns true if this [[Dataset]] contains one or more sources that
continuously return data as it arrives.
A [[Dataset]] that reads data from a streaming source must be executed as a
[[ContinuousQuery]] using
the `startStream()` method in [[DataFrameWriter]]. Methods that return a
single answer, (e.g., `count()` or
`collect()`) will throw an [[AnalysisException]] when there is a streaming
source present.
```
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