D-Wave Qubits 2025 - Constrained Quadratic Model for Optimizing Join Orders, Ibrahim Sabek, USC

At Qubits 2025, Ibrahim Sabek, assistant professor at USC Viterbi School of Engineering, explored the application of constrained quadratic models in optimizing database join orders. This session underscored the capabilities of quantum computing in solving combinatorial optimization problems, enhancing database query performance, and streamlining data operations for large-scale applications.

The query planner is a critical component of any database management system, responsible for
selecting the most cost-effective execution plan. A key challenge in query optimization is
determining the most efficient sequence for joining multiple relations in a database join query. Since the search space grows exponentially, finding the optimal join order is an NP-hard combinatorial optimization problem, making it increasingly difficult to obtain good solutions as the number of relations increases. While dynamic programming (DP) approaches can yield optimal solutions for small join queries, they become impractical for larger queries due to their exponential computational complexity. In this talk, he will present our recent efforts to optimize join orders in database applications using quantum computing. Our approach leverages a hybrid framework that combines classical heuristics with quantum processing to accelerate the search for optimal solutions. By formulating join order optimization as a Quadratic Unconstrained Binary Optimization (QUBO) problem, we implement it using the Constrained Quadratic Model (CQM), a hybrid classical quantum solver that integrates classical heuristics with D-Wave’s quantum annealer. Additionally,
we introduce the first Quantum-augmented Query Optimizer (Q2O), which incorporates quantum
computing into the end-to-end database workflow in a real-time setup. Experimental results
demonstrate that our approach enables faster query planning, achieving up to a 13x speedup in query execution.

About Qubits:
D-Wave’s annual quantum computing conference highlighted how quantum solutions are addressing real-world challenges in logistics, manufacturing, financial services, life sciences, and more. The conference featured groundbreaking work in quantum-fueled AI, optimization, and materials science, along with insights into the latest quantum hardware and software from D-Wave’s development team. Attendees had the chance to participate in hands-on technical sessions designed to accelerate the adoption of quantum computing in your organization.

Quantum isn’t decades away. It’s here today. Quantum Realized, brought to you by D-Wave.

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