Interactive query performance is becoming an important criterion for online systems where delivering query results in a timely fashion is critical. Pipelined execution is a promising query execution style that can produce the initial portion of the result early and in a continuous fashion. In this paper we propose techniques for delivering results faster in a pipelined query plan. We distinguish between two cases. For cases where the tuples in the query result are of the same importance we propose a dynamic rate-based pipeline scheduling policy that produces more results during the early stages of query execution. For cases where the result tuples have varying degrees of importance, we propose a dynamic tuple regulation algorithm that produces more important tuples during the early stages of query execution. Experimental results show that the proposed approaches significantly improve the interactive behavior in both cases.
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