stratosphere/stratosphere — pull request #544 by aljoscha (2014-03-07 19:48:10+00:00)
Title: Fix bug in MapNode

MapNode is responsible for PlainMapOperatorBase and not for
MapOperatorBase, but this is a mess right now.

Maybe we should think about cleaning the situation a bit. CollectorMap is the same as FlatMap, only the function in the interface is called map instead of flatMap. I know that this is because of historic reasons but it is still a mess because we handle all three types through the layers. For example, some code in PactCompiler looks like this:

```java
else if (c instanceof MapOperatorBase) {
n = new CollectorMapNode((MapOperatorBase) c);
}
else if (c instanceof PlainMapOperatorBase) {
n = new MapNode((PlainMapOperatorBase) c);
}
else if (c instanceof FlatMapOperatorBase) {
n = new FlatMapNode((FlatMapOperatorBase) c);
}
```