Query Processing: Relational Operations and Models

This lecture covers the fundamentals of query processing in data-intensive systems, focusing on relational operations such as selections, projections, and joins. It begins with an overview of the query processing steps, including parsing, rewriting, and optimizing SQL queries. The instructor explains two primary processing models: the iterator model and the materialization model, detailing how each operates and their respective advantages and disadvantages. The iterator model processes tuples one at a time, while the materialization model processes all tuples at once, which can be more efficient for certain workloads. The lecture also delves into the implementation of relational operators, discussing access methods like sequential scans and index scans. The instructor illustrates how selections can be optimized using indexes and discusses the importance of selectivity in query performance. Finally, the lecture introduces various join algorithms, including nested-loop joins, hash joins, and sort-merge joins, emphasizing their cost implications and efficiency in different scenarios.