Method and apparatus for object oriented storage and retrieval of data from a relational database

• US 20030204514A1
• Filed: 02/26/2003
• Published: 10/30/2003
• Est. Priority Date: 05/14/1997
• Status: Active Grant

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: Portal Software, Inc. (Oracle Corporation)
• Inventors: Labuda, David S., Owens, Gary L.
• Granted Patent: US 7,089,262 B2
• Time in Patent Office: Days
• US Class Current: 707/100
• CPC Class Codes: G06F 16/289 Object oriented databases
• CPC Class Codes: G06Q 40/02 Banking, e.g. interest calculation or account maintenance credit or loans G06Q40/03
• CPC Class Codes: Y10S 707/99934 Query formulation, input preparation, or translation
• CPC Class Codes: Y10S 707/99943 Generating database or data structure, e.g. via user interface
• CPC Class Codes: Y10S 707/99944 Object-oriented database structure

Abstract

Systems and methods for accessing a relational database through an object-oriented querying interface are provided. A class of objects that are to be stored in the relational database are defined. One or more relational database tables are created and a mapping is produced that maps each data member of an object to one or more columns in a relational database table. Additionally, object-oriented paradigms like inheritance may be supported and the allocation of storage for array elements may be deferred until necessary.

Claims

1. In a computer system, a method of storing objects in a relational database, comprising the steps of:

defining a class of objects that are to be stored in the relational database, the objects of the class having at least one data member;

mapping each data member to at least one column in at least one relational database table; and

creating the at least one relational database table to store the objects of the class.

2. The method of claim 1, wherein the defining step comprises the step of generating a hierarchical tree that represents a definition of the data members of the class of objects.

3. The method of claim 1, wherein the hierarchical tree stores a hierarchy of classes including the class.

4. The method of claim 1, wherein the creating step comprises the steps of:

generating SQL statements for creating the at least one relational database table; and

sending the SQL statements to a relational database management system.

5. The method of claim 1, further comprising the step of instantiating an object of the class by instantiating a container object to store data members of the object.

6. The method of claim 5, wherein the container object is created utilizing a hierarchical tree that represents a definition of the data members of the class of objects.

7. The method of claim 1, further comprising the step of defining a subclass of objects that are to be stored in the relational database, the objects of the subclass inheriting the data members of the class of objects and having at least one additional data member.

8. The method of claim 7, further comprising the step of generating a hierarchical tree that comprises a definition of the at least one additional data member.

9. The method of claim 7, further comprising the steps of:

generating SQL statements for creating an additional relational database table to store the at least one additional data member; and

sending the SQL statements to a relational database management system.

10. The method of claim 1, wherein the at least one data member of the objects of the class comprise an array.

11. The method of claim 1, wherein the defining step comprises the step of receiving input of characteristics of data members.

12. The method of claim 1, wherein a characteristic indicates the data member is mandatory, optional, or read only.

13. The method of claim 1, wherein a characteristic indicates a default value for the data member.

14. In a computer system, a method of querying a relational database, comprising the steps of:

receiving a first query that is object-oriented and specifies information about objects of interest;

instantiating a query container object that comprises a query template based on the first query, an array for any arguments in the template query, and an array for any results in the template query;

utilizing the query container object, translating the first query into a second query in a relational database query language for accessing the specified information about the objects of interest that are stored by a relational database management system;

sending the second query to the relational database management system; and

receiving the specified information about the objects of interest from the relational database management system.

15. The method of claim 14, further comprising the step of utilizing a hierarchical tree to map data members of objects of interest to columns in the relational database.

16. The method of claim 14, further comprising the step of instantiating a results container object to store the specified information about the objects of interest.

17. In a computer system, a method of deferring allocation of storage for array elements of objects comprising the steps of:

receiving a request to instantiate an object of a class where the class has a definition that specifies a default value for each data member of an array element;

allocating storage space for the object without storage space for an array element if the instantiation request does not specify an initial value for any of the data members of the array element;

receiving a request to modify a data member of the array element;

determining if storage space for the array element has been allocated;

if storage space for the array element has not been allocated, allocating storage space for the array element and initializing each data member of the array element to the specified default value; and

modifying the data member of the array element as specified in the modification request.

18. The method of claim 17, wherein each array element is stored as a row in a relational database table.

19. A computer system for storing objects in a relational database, comprising:

an object-oriented application for receiving a definition of a class of objects that are to be stored in the relational database, the objects being stored in a temporary storage;

a memory for the temporary storage of the objects;

an object server for retrieving the objects from the memory and issuing statements in a relational database query language to store data of the objects; and

a relational database management system for receiving the statements and storing the data of the objects in persistent storage as relational database tables.

20. The system of claim 19, further comprising a hierarchical tree that represents the definition of the class of objects including data members.

21. The system of claim 20, wherein the hierarchical tree stores a mapping from each data member of the class of objects to at least one column in the relational database tables.

22. The system of claim 20, wherein the hierarchical tree stores a hierarchy of classes including the class.