To optimize query parallelism techniques, substantial workloads are required with specific query plans and customized output size for each operator (denoted as cardinality constraint). To this end, a rich body of query-aware database generators (QAG) are proposed. However, the complex data dependencies hidden behind queries make previous QAGs suffer from deficiencies in supporting complex operators and controlling the generation errors. In this paper, we design a new generator Mirage supporting well for complex operators with low error bounds for cardinality constraints. First, Mirage leverages Query Rewriting and Set Transforming Rules to decouple dependencies between key and non-key columns, which could help generate each of them individually. Then, for the non-key columns, Mirage abstracts cardinality constraints of operators as placement requirements within each column's domain, and further models the generation problem as a classic bin packing problem. Finally, for the key columns, Mirage proposes a uniform representation of join cardinality constraints for all types of PK-FK joins and partitions the data according to the matching status between PK and F K columns. Then, it formulates the key population as a Constraint Programming problem, which can be solved by an existing CP Solver. The experiments show that Mirage conquers all previous work in either operator support or generation error.

Generating synthetic workloads is essential and critical to the performance evaluation of database systems. When benchmarking database performance for a specific application, the similarity between synthetic workloads and real application workloads determines the credibility of the evaluation results. However, it meets a great challenge to catch workload characteristics for a target online transaction processing (OLTP) application considering the complexity of transaction executions. To address this problem, we propose a workload duplicator (Lauca) that can generate synthetic workloads with highly similar performance metrics compared to a specific application on both centralized and distributed databases. By carefully studying the application-driven workload generation problem, we presentTransaction Logic,Data Access DistributionandPartition Access Distributionto characterize runtime workloads and propose novel generation algorithms to guarantee the high fidelity of synthetic workloads. To the best of our knowledge, Lauca is the first application-driven transactional workload generator. We conduct extensive experiments based on TPC-C, SmallBank and YCSB on both centralized and distributed databases. The experimental results show that Lauca consistently generates high-quality synthetic workloads.

Query-aware synthetic data generation is an essential and highly challenging task, important for database management system (DBMS) testing, database application testing and application-driven benchmarking. Prior studies on query-aware data generation suffer common problems of limited parallelization, poor scalability, and excessive memory consumption, making these systems unsatisfactory to terabyte scale data generation. In order to fill the gap between the existing data generation techniques and the emerging demands of enormous query-aware test databases, we design and implement a new data generator, called Touchstone. Touchstone adopts the random sampling algorithm instantiating query parameters and the new data generation schema generating the test database, to achieve fully parallel data generation, linear scalability and austere memory consumption. It has full support of outer joins as well as non-equi-joins for application-oriented data generation. Our experimental results show that Touchstone consistently outperforms the state-of-the-art solution on TPC-H workload by a 1000 speedup without sacrificing simulation fidelity.