A question that database administrators (DBAs) routinely need to answer is how long a batch query workload will take to complete. This question arises, for example, while planning the execution of different report-generation workloads to fit within available time windows. To answer this question accurately, we need to take into account that the typical workload in a database system consists of mixes of concurrent queries. Interactions among different queries in these mixes need to be modeled, rather than the conventional approach of considering each query separately. This paper presents a new approach for estimating workload completion times that takes the significant impact of query interactions into account. This approach builds performance models using an experiment-driven technique, by sampling the space of possible query mixes and fitting statistical models to the observed performance at these samples. No prior assumptions are made about the internal workings of the database system or the cause of query interactions, making the models robust and portable. We show that a careful choice of sampling and statistical modeling strategies can result in accurate models, and we present a novel interaction-aware workload simulator that uses these models to estimate workload completion times. An experimental evaluation with complex TPC-H queries on IBM DB2 shows that this approach consistently predicts workload completion times with less than 20% error.

While planning the execution of report-generation workloads, database administrators often need to know how long different query workloads will take to run. Database systems run mixes of multiple queries of different types concurrently. Hence, estimating the completion time of a query workload requires reasoning about query mixes and inter-query interactions in the mixes; rather than considering queries or query types in isolation. This paper presents a novel approach for estimating workload completion time based on experiment-driven modeling and simulation of the impact of inter-query interactions. A preliminary evaluation of this approach with TPC-H queries on IBM DB2 shows how our approach can consistently predict workload completion times with good accuracy.

The typical workload in a database system consists of a mixture of multiple queries of different types, running concurrently and interacting with each other. Hence, optimizing performance requires reasoning about query mixes and their interactions, rather than considering individual queries or query types. In this paper, we show the significant impact that query interactions can have on workload performance. We present a new approach based on planning experiments and statistical modeling to capture the impact of query interactions. This approach requires no prior assumptions about the internal workings of the database system or the nature or cause of query interactions, making it portable across systems. As a concrete demonstration of the potential of capturing, modeling, and exploiting query interactions, we develop a novel interaction-aware query scheduler that targets report-generation workloads in Business Intelligence (BI) settings. Under certain assumptions, the schedule found by this scheduler is within a constant factor of optimal. An experimental evaluation with TPC-H queries on IBM DB2 demonstrates that our scheduler consistently outperforms (up to 4x) conventional schedulers that do not account for query interactions.

The typical workload in a database system consists of a mixture of multiple queries of different types, running concurrently and interacting with each other. Hence, optimizing performance requires reasoning about query mixes and their interactions, rather than considering individual queries or query types. In this paper, we use such a reasoning approach to develop a query scheduler. We treat the database system as a black box and experimentally build a model to estimate the performance of different query mixes. Our scheduler uses this model to decide which query mixes to schedule, with the goal of maximizing throughput. We experimentally demonstrate the effectiveness of our scheduler using queries from the TPC-H benchmark on DB2.