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Type:
Improvement
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Status: Open
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Priority:
Major
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Resolution: Unresolved
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Affects Version/s: 1.4.0
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Fix Version/s: None
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Component/s: API / DataSet, API / DataStream, API / Scala
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Labels:None
A collect function is a method that takes a Partial Function as its parameter and applies it to all the elements in the collection to create a new collection which satisfies the Partial Function.
It can be found on all core scala collection classes as well as on spark's rdd interface
To understand its utility imagine the following scenario :
Given a DataStream that produces events of type Purchase and View
Transform this stream into a stream of purchase amounts over 1000 euros.
Currently an implementation might look like
val x = dataStream .filter(_.isInstanceOf[Purchase]) .map(_.asInstanceOf[Purchase]) .filter(_.amount > 1000) .map(_.amount)
Or alternatively you could do this
dataStream.flatMap(_ match {
case p: Purchase if p.amount > 1000 => Some(p.amount)
case _ => None
})
But with collect implemented it could look like
dataStream.collect {
case p: Purchase if p.amount > 1000 => p.amount
}
Which is a lot nicer to both read and write
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