1. One or more computer-readable storage devices comprising computer-executable instructions for optimizing a performance of a data processing job, the computer-executable instructions directed to steps comprising: selecting a computer-executable program that includes a first set of operations to carry out the data processing job; augmenting at least some operations, of the first set of operations, in the computer-executable program to comprise computer-executable instructions for collecting execution statistics quantifying execution of the augmented operations, the execution statistics being indicative of at least the runtime performance of the first set of operations; receiving at least some of the execution statistics prior to the data processing job having been completed; selecting, based on the received execution statistics, a second set of operations that are semantically equivalent to the first set of operations, the semantically equivalent second set of operations different but functionally equivalent to the first set of operations and configured to provide a same result as the first set of operations; and proceeding with the data processing job with the second set of operations.