Reducing the domain of a subquery by retrieving constraints from the outer query

US10642832B1 · kind B1 · utility

Assignee

• Tableau Software, Inc. · US

Inventors

• Thomas Neumann · Munich, DE
• Viktor Leis · Munich, DE
• Alfons Kemper · Munich, DE

Key dates

• Filing date: Sep 15, 2017
• Grant date: May 5, 2020
• Expiry date: Aug 31, 2038

Classification

• Technology area (CPC H): Electricity
• CPC primary: H03M7/705
• WIPO field: Computer technology
• WIPO sector: Electrical engineering

Abstract

A database engine receives a human-readable database query that includes a subquery, and parses the database query to build an operator tree. The operator tree includes a subtree corresponding to the subquery. The database engine estimates the number of rows that will accessed when the subtree is executed and estimates the fraction of the cardinality of rows that will be filtered out by subsequent operations in the operator tree. In accordance with a determination that the estimated fraction exceeds a first threshold, the database engine inserts a domain constraint into the subtree that restricts rows retrieved by execution of the subtree, thereby forming a modified operator tree. The database engine executes the modified operator tree to form a final result set corresponding to the database query and returns the final result set.