Bitmap-based count distinct query rewrite in a relational SQL algebra
US11379476B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Oct 15, 2019 |
| Grant date | Jul 5, 2022 |
| Priority date | — |
| Expiry date | Apr 10, 2040 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F16/2454
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
Techniques are described for storing and maintaining, in a materialized view, bitmap data that represents a bitmap of each possible distinct value of an expression and rewriting a query for a count of distinct values of the expression using the materialized view. The materialized view contains bitmap data that represents a bitmap of each possible distinct value of a first expression, and aggregate values of additional expressions, and is stored in memory or on disk by a database system. The database system receives a query that requests a number of distinct values, of the first expression, and an aggregate value for an additional expression. In response, the database system, rewrites the query to: compute the number of distinct values by counting the bits in the bitmap data of the materialized view that are set to the first value, and obtains the aggregate value for the additional expression in the materialized view.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.