Hung-chih Yang, Ali Dasdan, Ruey-Lung Hsiao, Douglas Stott Parker Jr.. Map-reduce-merge: simplified relational data processing on large clusters. In Chee Yong Chan, Beng Chin Ooi, Aoying Zhou, editors, Proceedings of the ACM SIGMOD International Conference on Management of Data, Beijing, China, June 12-14, 2007. pages 1029-1040, ACM, 2007. [doi]
Map-Reduce is a programming model that enables easy development of scalable parallel applications to process a vast amount of data on large clusters of commodity machines. Through a simple interface with two functions, map and reduce, this model facilitates parallel implementation of many real-world tasks such as data processing jobs for search engines and machine learning.
However,this model does not directly support processing multiple related heterogeneous datasets. While processing relational data is a common need, this limitation causes difficulties and/or inefficiency when Map-Reduce is applied on relational operations like joins.
We improve Map-Reduce into a new model called Map-Reduce-Merge. It adds to Map-Reduce a Merge phase that can efficiently merge data already partitioned and sorted (or hashed) by map and reduce modules. We also demonstrate that this new model can express relational algebra operators as well as implement several join algorithms.