Hash-based database grouping system and method
US5511190A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 20, 1995 |
| Grant date | Apr 23, 1996 |
| Priority date | — |
| Expiry date | Jan 20, 2015 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S707/99931
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A structured query language (SQL) grouping and aggregation system and method that incorporates hash-based techniques, several overflow handling strategies and statistics-based process-selection criteria. The method can execute SQL group-by queries on distributed database tables or tables stored locally to the database management system (DBMS) processor executing the grouping method. Hash-based techniques allow groupings and aggregates to be generated on the fly through the use of partial aggregates maintained in primary memory. Where primary memory is limited, groups and aggregates are still generated for as many groups as can be maintained in primary memory, while various overflow procedures are provided for buffering ungrouped data and writing that data to an overflow disk file for later processing. In one overflow procedure, raw data from groups that cannot be aggregated in primary memory are buffered then written to the overflow disk file. In a second overflow procedure, ungroupable raw data is formatted the same as data being aggregated in the group table, buffered, and then written to the overflow file. In a third overflow procedure, ungroupable raw data is partially aggregat…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.