The present invention generally relates to systems and methods for executing scripts (a sequence of declarative operations) on large data sets. Some implementations store descriptions of previously-executed operations and associated input and output data sets. When executing similar operations on the same, a subset of, a superset of, or any fragment of data subsequently, some implementations detect duplication of operations and access previously-stored output data sets in order to re-use data and reduce the amount of execution, thus avoiding time-consuming duplicative computations.