Persistent stream for processing time consuming and reusable queries in an object oriented database management system

• US 5,161,225 A
• Filed: 10/23/1989
• Issued: 11/03/1992
• Est. Priority Date: 10/23/1989
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Priven, Michael P., Abraham, Robert L.
• Primary Examiner(s): Heckler, Thomas M.
• Application Number:
  US07/425,747
• Time in Patent Office: 1,107 Days
• Field of Search: 364/DIG. 1 MS File, 364/DIG. 2 MS File, 395/600
• US Class Current: 1/1
• CPC Class Codes: G06F 16/289 Object oriented databases
• CPC Class Codes: Y10S 707/99932 Access augmentation or optimizing
• CPC Class Codes: Y10S 707/99944 Object-oriented database structure

Abstract

Time consuming and reusable queries are handled in an object oriented database management system by providing a persistent stream object class. The persistent stream object class is a subclass of the stream class which is typically provided to encapsulate the results of a query. The persistent stream class inherits all the attributes and methods of the stream class but also includes a "save" method for saving the results of a query. When a query names a persistent stream as it object, the query results are saved. The query may also be performed in background or batch mode. All time consuming and reusable queries are performed by sending a query message to the persistent stream class, to thereby automatically save the query results.

Claims

1. An object oriented database management system comprising:

a data storage device;

a database of data objects stored in said data storage device;

a data processor connected to said data storage device;

an object oriented database manager operating in said data processor, for performing queries of said database of data objects, said database manager including a stream class and a persistent stream class of objects;

said stream class of objects comprising a plurality of stream class attributes and at least one stream class method, said stream class attributes comprising a list of data objects which result from a query performed by said object oriented database manager; and

said persistent stream class of objects comprising a plurality of persistent stream class attributes and at least one persistent stream class method, said persistent stream class being organized as a subclass of said stream class to thereby inherit said stream class attributes and said at least one stream class method, said at least one persistent stream class method further comprising a save method for saving the list of data objects which result from a query performed by said object oriented database manager in said data storage device.

2. The object oriented database management system of claim 1 wherein said save method comprises:

means for allocating a location in said data storage device for saving therein the list of data objects which result from a query;

means for obtaining the list of data objects which result from a query;

means for saving the list of data objects which results from a query in the allocated location; and

means for indicating that the list of data objects which result from a query have been obtained and saved.

3. The object oriented database management system of claim 2 wherein said means for obtaining comprises means for serially obtaining each data object in said database which results from the query.

4. The object oriented database management system of claim 3 wherein said means for saving comprises means for saving each data object in said database which results from the query, in the allocated location in the data storage device.

5. The object oriented database management system of claim 2 wherein said persistent stream class attributes further comprise a first indicator of whether the list of data objects which result from a query have been saved in said data storage device, and a second indicator of the location in said data storage device where the list of data objects which result from a query have been saved, and wherein said means for indicating comprises means for setting said first indicator and means for placing the allocated location into said second indicator.

6. The object oriented database management system of claim 1 wherein said database manager further comprises:

means for accepting a query to be performed on said database of data objects;

means for determining whether an accepted query is to be saved;

means for sending a query message to said persistent stream class object if an accepted query is to be saved; and

means for sending a query message to said stream class if an accepted query is not to be saved.

7. The object oriented database management system of claim 6 wherein said determining means comprises means for accepting an indication that an accepted query is to be performed immediately;

and means for determining that an accepted query is not to be saved if the accepted query is to be performed immediately.

8. The object oriented database management system of claim 6 wherein said determining means comprises means for accepting an indication that the accepted query is to be reused;

and means for determining that an accepted query is to be saved if the accepted query is to be reused.

9. The, object oriented database management system of claim 6 wherein said determining means comprises means for estimating the time required for processing an accepted query, and means for determining that an accepted query is to be saved if the estimated processing time exceeds a predetermined time.

10. The object oriented database management system of claim 1 wherein said data storage device comprises a nonvolatile data storage device.

11. The object oriented database management system of claim 10 wherein said nonvolatile data storage device comprises a direct access storage device.

12. The object oriented database management system of claim 1 wherein said persistent stream class attributes further comprise a list of query criteria for a query.

13. The object oriented database management system of claim 1 wherein said persistent stream class attributes further comprise a first indicator of whether the list of data objects which result from a query have been saved in said data storage device, and a second indicator of the location in said data storage device where the list of data objects which result from a query have been saved.

14. The object oriented database management system of claim 1 wherein said at least one stream class method comprises create, open, get, close and delete methods.

15. A process for saving query results in an object oriented database management system comprising a data storage device having a database of data objects stored therein and a data processor connected to the data storage device and having an object oriented database manager operating therein for performing queries of said database, said query saving process comprising the steps of:

providing a stream class of objects comprising a plurality of stream class attributes and at least one stream class method, said stream class attributes comprising a list of data objects which result from a query performed by the object oriented database manager;

providing a persistent stream class of objects comprising a plurality of persistent stream attributes and at least one persistent stream class method, said at least one persistent stream class method comprising a save method for saving the list of data objects which result from a query in said data storage device; and

arranging said persistent stream class to be a subclass of said stream class, said persistent stream class thereby inheriting said stream class attributes and said at least one stream class method.

16. The query result saving process of claim 15 wherein said save method performs the steps of:

allocating a location in said data storage device for saving therein the list of data objects which result from a query;

obtaining the list of data objects which result from a query;

saving the list of data objects which results from a query in the allocated location; and

indicating that the list of data objects which result from a query have been obtained and saved.

17. The query result saving process of claim 16 wherein said obtaining step comprises the step of repeatedly obtaining each data object in said database which results from the query.

18. The query result saving process of claim 17 wherein said saving step comprises the step of serially saving each data object in said database which results from the query, in the allocated location in the data storage device.

19. The query result saving process of claim 16 wherein said persistent stream class attributes further comprise a first indicator of whether the list of data objects which result from a query have been saved in said data storage device, and a second indicator of the location in said data storage device where the list of data objects which result from a query have been saved, and wherein said indicating step comprises the step of setting said first indicator, and placing the allocated location into said second indicator.

20. The query result saving process of claim 15 further comprising the steps of:

accepting queries to be performed on said database of data objects;

determining whether an accepted query is to be saved;

sending a query message to said persistent stream class if an accepted query is to be saved; and

sending a query message to said stream class if an accepted query is not to be saved.

21. The query result saving process of claim 20 wherein said determining step comprises the steps of:

accepting an indication that an accepted query is to be performed immediately; and

determining that an accepted query is not to be saved if the accepted query is to be performed immediately.

22. The query result saving process of claim 20 wherein said determining step comprises the steps of:

accepting an indication that an accepted query is to be reused; and

determining that an accepted query is to be saved if the accepted query is to be reused.

23. The query result saving process of claim 20 wherein said determining step comprises the steps of:

estimating the time required for processing an accepted query; and

determining that an accepted query is to be saved if the estimated processing time exceeds a predetermined time.

24. The query result saving process of claim 15 wherein said persistent stream class attributes further comprise a list of query criteria for a query.

25. The query result saving process of claim 15 wherein said persistent stream class attributes further comprise a first indicator of whether the list of data objects which result from a query have been saved in said data storage device, and a second indicator of the location in said data storage device where the list of data objects which result from a query have been saved.