The present invention generally relates to data processing and, more particularly, to managing operation of user-defined functions on a partitioned database. One embodiment provides a computer-implemented method for managing execution of a query against a partitioned database having a plurality of data partitions. The method comprises, for each of the plurality of data partitions, examining data of the data partition, and on the basis of examined data, implementing a modified form of a user-defined function on the data partition. The method further comprises executing the query referring to the user-defined function against the plurality of data partitions, wherein execution of the query on each data partition invokes execution of the respective modified form of the user-defined function against the data of the respective data partition.