Oracle Corporation
Group-by efficiency though functional dependencies and non-blocking aggregation functions

Abstract:

Techniques described herein proposes a Dependent Grouping Column Rewrite that simplifies a grouping operation by excluding dependent grouping columns from a group by clause. A non-blocking aggregation function is applied to dependent grouping columns in at least select clauses. Such a simplified grouping operation reduces memory pressure, speeds up grouping operations, and saves compute time, as grouping columns that have no additional effect on the grouping operation are excluded from processing (e.g., hashing and key matching).