Method and apparatus for optimizing a merge-join operation across heterogeneous databases
US5903893A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 15, 1997 |
| Grant date | May 11, 1999 |
| Priority date | — |
| Expiry date | Sep 15, 2017 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F16/2456
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
An improved join operation is performed between data in at least two tables, with one of the tables stored in a remote database (hereafter "remote table") and another table stored in a local database (hereafter "local table"). The entry values in both the local table and the remote table are accessible in an ordered manner, based upon an order of the entry values. The method of the join operation generally includes the steps of: determining a count of a number of entry values that reside in the local table that are to be joined with entry values in the remote table; comparing the count with a threshold value, and (i) if the count exceeds the threshold value, issuing a query to the remote table to fetch a range of entry values therefrom, the range determined by the range of entry values to be joined from the local table; and (ii) if the count does not exceed the threshold value, issuing a query to the remote table to fetch each specific entry value that matches the entry values to be joined from the local table.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.