That's the just transform function in DataFrame
/**
* Concise syntax for chaining custom transformations.
* {{{
* def featurize(ds: DataFrame) = ...
*
* df
* .transform(featurize)
* .transform(...)
* }}}
* @since 1.6.0
*/
def transform[U](t: DataFrame
oogle Cloud Dataflow provides distributed dataset which called PCollection,
and syntactic sugar based on PCollection is provided in the form of
"apply". Note that "apply" is different from spark api "map" which passing
each element of the source through a function func. I wonder can spark
support
