Optimization and Evaluation of Nested Queries and Procedures
Ravindra Guravannavar
TL;DR
This paper addresses optimizing nested SQL queries and procedural code by proposing heuristics for sort order selection and techniques for batching parameters, resulting in significant performance improvements.
Contribution
It introduces practical heuristics for optimizing nested queries and a method for automating parameter batching in procedural database code.
Findings
Heuristics effectively improve query optimization.
Parameter batching significantly enhances performance.
Experimental results show notable performance gains.
Abstract
Many database applications perform complex data retrieval and update tasks. Nested queries, and queries that invoke user-defined functions, which are written using a mix of procedural and SQL constructs, are often used in such applications. A straight-forward evaluation of such queries involves repeated execution of parameterized sub-queries or blocks containing queries and procedural code. An important problem that arises while optimizing nested queries as well as queries with joins, aggregates and set operations is the problem of finding an optimal sort order from a factorial number of possible sort orders. We show that even a special case of this problem is NP-Hard, and present practical heuristics that are effective and easy to incorporate in existing query optimizers. We also consider iterative execution of queries and updates inside complex procedural blocks such as…
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Taxonomy
TopicsAdvanced Database Systems and Queries · Data Management and Algorithms · Web Data Mining and Analysis