Query processing for SQL updates

摘要

A rich set of concepts and techniques has been developed in the context of query processing for the efficient and robust execution of queries. So far, this work has mostly focused on issues related to data-retrieval queries, with a strong backing on relational algebra. However, update operations can also exhibit a number of query processing issues, depending on the complexity of the operations and the volume of data to process. Such issues include lookup and matching of values, navigational vs. set-oriented algorithms and trade-offs between plans that do serial or random I/Os.In this paper we present an overview of the basic techniques used to support SQL DML (Data Manipulation Language) in Microsoft SQL Server. Our focus is on the integration of update operations into the query processor, the query execution primitives required to support updates, and the update-specific considerations to analyze and execute update plans. Full integration of update processing in the query processor provides a robust and flexible framework and leverages existing query processing techniques.