tAggregateRow – accepts input data even if it is not sorted
tAggregateSortedRow– accepts only sorted input , if data is not sorted before this component, job goes into infinite loop.
Hence tSortRow component must be used before taggregatesortedrow if input data to this component is not sorted already.
tAggregateRow – Number of input rows to this component, need not be specified.
tAggregateSortedRow– Number of input rows to this component, must be specified.
if not sure about no of rows that are going to flow from this component to next component then you can specify -1 there.
3. standard deviation and union(geometry) :- these two operations are available only in taggregateRow. But who uses them :p ?