What's wrong with Map+ Reduce? Join combines inputs of different types Split produces outputs of different types Parse a document, output text and references Can be done with Map+Reduce Ugly to program Hard to avoid performance penalty Some merge joins very expensive Need to materialize entire cross product to diskWhat’s wrong with Map+Reduce? • Join combines inputs of different types • “Split” produces outputs of different types – Parse a document, output text and references • Can be done with Map+Reduce – Ugly to program – Hard to avoid performance penalty – Some merge joins very expensive • Need to materialize entire cross product to disk