Sort all valid elements according to a list of attribute values.
attributes: The list of attribute names to use for sorting
ascending:Optional boolean values that flags, if the given list of attributes should be sorted in ascending or descending order. Default value is descending.
Note: Because of the non-decreasing order of time in a data stream sorting is only possible inside a relation with equal start and end timestamp.Output is only created after an element is read with a higher start time stamp than the highest end timestamp!
So in the following example, output is created after reading the last "a"-value.
a [0,10] --> no output
c [0,10] --> no output
b [0,10] --> no output
a [10,20] --> Output of three tuples a [0,10], b [0,10], c [0,10]