1. A computer program product for stratified sampling of a plurality of records, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable by a processor to, in a mapreduce framework: partition a plurality of records into a plurality of splits, wherein each split includes at least a portion of the plurality of records; provide at least one split of the plurality of splits to a mapper, wherein the mapper scans the input data set, transforms each input record using a map function, and extracts a grouping key in parallel; assign at least a portion the records of the at least one split to a group, wherein each assignment to the group is based on a strata of the assigned record; filter the records of the group, wherein each filtering is based on a comparison of a weight of a record to a local threshold of the mapper; shuffle the group to a reducer; and provide a stratified sampling of the plurality of records based on the group.