PostgreSQL Query Plans for Aggregating Data

This text discusses data aggregation operations in databases, including grouping rows by a certain column, calculating sums, maximum or minimum values of a column, and selecting distinct values of a column. It explains the use-cases of different aggregation nodes such as Aggregate, HashAggregate, GroupAggregate, Unique, and how they are used in query plans. The text also covers parallelized aggregation nodes and their role in handling large datasets. Various examples are provided to illustrate these concepts using a flight tickets mid-sized database.