Relational Databases for Biologists Tutorial – ISMB02

As an example of how queries are executed, consider the query shown in Figure 5. In Figure 6, the processes used to execute the query are shown along with the flow of data between the various processes for a Gamma configuration consisting of two processors with disks and two processors without disks. Since the two input rela- tions A and B are partitioned across the disks attached to processors P1 and P2, selection and scan operators are ini- tiated on both processors P1 and P2. The split tables for both the select and scan operators each contain two entries since two processors are being used...