Database Systems: Concepts, Design and Applications

11.7. Pipelining and Materialization

When a query is composed of several relational algebra operators, the result of one operator is sometimes pipelined to another operator without creating a temporary relation to hold the intermediate result. When the input relation to a unary operation (for example, selection or projection) is pipelined into it, it is sometimes said that the operation is applied on-the-fly. Pipelining (or on-the-fly processing) is sometimes used to improve the performance of the queries. As we know that the results of intermediate algebra operations are stored on the secondary storage or disk, which are temporarily written. If the output of an operator operation is saved in a temporary relation for processing by the next operator, ...