System, method, and computer program product for efficiently translating relational tuples to object-oriented objects

• US 5,893,108 A
• Filed: 08/28/1997
• Issued: 04/06/1999
• Est. Priority Date: 12/29/1994
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Parvathaneny, Bhaskar, Srinivasan, Venkatachary
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): Corrielus, Jean M.
• Application Number:
  US08/919,176
• Time in Patent Office: 586 Days
• Field of Search: 707/1, 707/103, 711/118
• US Class Current: 1/1
• CPC Class Codes: G06F 16/289 Object oriented databases
• CPC Class Codes: Y10S 707/99944 Object-oriented database structure

Abstract

A procedure for translating tuples received from a relational database management system (RDBMS) to object-oriented objects is described. The procedure operates by instantiating one or more application objects, and then setting base attributes of the application objects using information in the tuples. One or more intermediate objects are created using information in the tuples to represent those application objects having relationship attributes requiring dereferencing. Relationship attributes in the application objects are then set by swizzling the intermediate objects (rather than by swizzling the application objects themselves).

Claims

1. A computer program product comprising a computer readable medium having computer program logic recorded thereon for enabling a processor in a computer system to provide access to a database management system from an object-oriented environment, the database management system including a plurality of tuples, said computer program product comprising:

receiving means for enabling said processor to receive an object query from the object oriented environment;

first generating means for enabling said processor to generate a set of relational database queries in response to receiving the object query, said set of relational database queries used to retrieve tuples from the database management system;

second generating means for enabling said processor to generate one or more application objects in response to receiving said tuples from the database management system, said second generating means comprising;

application object instantiation means for enabling said processor to instantiate said one or more application objects;

base attribute setting means for enabling said processor to set base attributes of said one or more application objects using information in said tuples;

intermediate object creating means for enabling said processor to create one or more intermediate objects using information in said tuples to represent relationship attributes of said one or more application objects requiring dereferencing; and

relationship attribute setting means for enabling said processor to set relationship attributes in said one or more application objects by swizzling said intermediate objects.

2. The computer program product of claim 1, wherein said base attribute setting means comprises:

means for enabling said processor to set base attributes of said application objects using information in said tuples which map to said base attributes.

3. The computer program product of claim 1, wherein said intermediate object creating means comprises:

means for enabling said processor to select one of said application objects having relationship attributes requiring dereferencing;

means for enabling said processor to generate an intermediate object having a self pointer field, a self key field, a foreign pointer field, and a foreign key field;

means for enabling said processor to set said self pointer field to point to said selected application object; and

means for enabling said processor to set said self key field to be equal to a primary key of a tuple that maps to said selected application object.

4. The computer program product of claim 3, wherein said intermediate object creating means further comprises:

means for enabling said processor to set said foreign key field equal to a foreign key stored in said tuple.

5. The computer program product of claim 4, wherein said relationship attribute setting means comprises:

means for enabling said processor to identify a second intermediate object having a self key field equal to said foreign key field of said first intermediate object; and

means for enabling said processor to set said foreign pointer field of said first intermediate object equal to a self pointer field of said second intermediate object.

6. The computer program product of claim 5, wherein said relationship attribute setting means further comprises:

means for enabling said processor to set a relationship attribute of said selected application object equal to said foreign pointer field of said first intermediate object.

7. The computer program product of claim 1, wherein said application object instantiation means comprises:

means for enabling said processor to select one of said tuples;

means for enabling said processor to reference an object table to determine whether an application object associated with said selected tuple already exists; and

means for enabling said processor to instantiate a new application object for said selected tuple if one does not already exist.

8. The computer program product of claim 7, wherein said application object instantiation means further comprises:

means for enabling said processor to create a new entry in said object table to represent said new application object.

9. The computer program product of claim 1, wherein said intermediate object creating means comprises:

means for enabling said processor to generate a first intermediate object to represent a first application object of a first class, said first application object having a relationship attribute requiring dereferencing according to a many-to-many relationship, said first intermediate object having a self pointer field, a self key field, and an array of foreign pointers field;

means for enabling said processor to generate a second intermediate object to represent a second application object of a second class, said second application object having a relationship attribute requiring dereferencing according to said many-to-many relationship, said second intermediate object having a self pointer field, a self key field, and an array of foreign pointers field;

means for enabling said processor to set said self pointer fields in said first and second intermediate objects to point to said first and second application objects, respectively; and

means for enabling said processor to set said self key fields in said first and second intermediate objects to be equal to primary keys of tuples that map to said first and second application objects, respectively.

10. The computer program product of claim 9, wherein said first and second classes are the same.

11. The computer program product of claim 9, wherein said intermediate object creating means further comprises:

means for enabling said processor to generate IT (intermediate table) intermediate objects to represent tuples read from an intermediate table; and

IT intermediate object initializing means for enabling said processor to initialize said IT intermediate objects from information contained in said intermediate table tuples such that each IT intermediate object indicates a link between an application object of said first class and an application object of said second class.

12. The computer program product of claim 11 in which each intermediate table tuple stores a first primary key identifying an application object of said first class, and a second primary key identifying an application object of said second class, wherein said IT intermediate object initializing means comprises:

means for enabling said processor to store in said IT intermediate objects first and second primary keys from intermediate table tuples respectively mapping to said IT intermediate objects.

13. The computer program product of claim 11, wherein said relationship attribute setting means comprises:

means for enabling said processor to initialize said array of foreign pointers field in said first and second intermediate objects by referring to information in said IT intermediate objects;

means for enabling said processor to set a relationship attributes array in said first application object equal to said array of foreign pointers field in said first intermediate object; and

means for enabling said processor to set a relationship attributes array in said second application object equal to said array of foreign pointers field in said second intermediate object.

14. The computer program product of claim 1, further comprising means for storing a mapping schema which maps a schema for the database management system into a schema for the object oriented environment, and wherein said generating means generating one or more application objects comprises means for examining the mapping schema to determine attributes which are base attributes and which require dereferencing, the means for examining making the determination in response to receiving the object query.

15. The computer program product of claim 14, wherein the database management system is a relational database management system.

16. The computer program product of claim 15, wherein each intermediate object includes a foreign key pointer field for each of the foreign keys included in a relational table which maps to a class corresponding to said one or more application objects.

17. A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform method steps for providing access to a database management system from an object-oriented environment, the database management system including a plurality of tuples, said method steps comprising:

receiving an object query from the object oriented environment;

generating a set of relational database queries in response to receiving the object query;

retrieving tuples from the database management system using said set of relational database queries;

generating one or more application objects in response to receiving said tuples from the database management system, the step of generating comprising the steps of;

(1) instantiating said one or more application objects;

(2) setting base attributes of said one or more application objects using information in said tuples;

(3) creating one or more intermediate objects using information in said tuples to represent relationship attributes of said one or more application objects requiring dereferencing; and

(4) setting relationship attributes in said one or more application objects by swizzling said intermediate objects.

18. The program storage device of claim 17, wherein step (2) comprises the step of:

setting base attributes of said application objects using information in said tuples which map to said base attributes.

19. The program storage device of claim 17, wherein step (3) comprises the steps of:

(a) selecting one of said application objects having relationship attributes requiring dereferencing;

(b) generating an intermediate object having a self pointer field, a self key field, a foreign pointer field, and a foreign key field;

(c) setting said self pointer field to point to said selected application object; and

(d) setting said self key field to be equal to a primary key of a tuple that maps to said selected application object.

20. The program storage device of claim 19, wherein step (3) further comprises the step of:

(e) repeating steps (a)-(d) for each of said application objects having relationship attributes requiring dereferencing.

21. The program storage device of claim 19, wherein step (3) further comprises the step of:

(e) setting said foreign key field equal to a foreign key stored in said tuple.

22. The program storage device of claim 21, wherein step (4) comprises the steps of:

(a) identifying a second intermediate object having a self key field equal to said foreign key field of said first intermediate object; and

(b) setting said foreign pointer field of said first intermediate object equal to a self pointer field of said second intermediate object.

23. The program storage device of claim 22, wherein step (4) further comprises the step of:

(c) setting a relationship attribute of said selected application object equal to said foreign pointer field of said first intermediate object.

24. The program storage device of claim 17, wherein step (1) comprises the steps of:

(a) selecting one of said tuples;

(b) referencing an object table to determine whether an application object associated with said selected tuple already exists; and

(c) instantiating a new application object for said selected tuple if one does not already exist.

25. The program storage device of claim 24, wherein step (1) further comprises the step of:

(d) repeating steps (a)-(c) for each of said tuples.

26. The program storage device of claim 24, wherein step (1) further comprises the step of:

(d) creating a new entry in said object table to represent said new application object.

27. The program storage device of claim 17, wherein step (3) comprises the steps of:

(a) generating a first intermediate object to represent a first application object of a first class, said first application object having a relationship attribute requiring dereferencing according to a many-to-many relationship, said first intermediate object having a self pointer field, a self key field, and an array of foreign pointers field;

(b) generating a second intermediate object to represent a second application object of a second class, said second application object having a relationship attribute requiring dereferencing according to said many-to-many relationship, said second intermediate object having a self pointer field, a self key field, and an array of foreign pointers field;

(c) setting said self pointer fields in said first and second intermediate objects to point to said first and second application objects, respectively; and

(d) setting said self key fields in said first and second intermediate objects to be equal to primary keys of tuples that map to said first and second application objects, respectively.

28. The program storage device of claim 27, wherein said first and second classes are the same.

29. The program storage device of claim 27, wherein step (3) further comprises the steps of:

(e) generating IT (intermediate table) intermediate objects to represent tuples read from an intermediate table; and

(f) initializing said IT intermediate objects from information contained in said intermediate table tuples such that each IT intermediate object indicates a link between an application object of said first class and an application object of said second class.

30. The program storage device of claim 29 in which each intermediate table tuple stores a first primary key identifying an application object of said first class, and a second primary key identifying an application object of said second class, wherein step (f) comprises the step of:

storing in said IT intermediate objects first and second primary keys from intermediate table tuples respectively mapping to said IT intermediate objects.

31. The program storage device of claim 29, wherein step (4) comprises the steps of:

(a) initializing said array of foreign pointers field in said first and second intermediate objects by referring to information in said IT intermediate objects;

(b) setting a relationship attributes array in said first application object equal to said array of foreign pointers field in said first intermediate object; and

(c) setting a relationship attributes array in said second application object equal to said array of foreign pointers field in said second intermediate object.

32. The program storage device of claim 17, further comprising the step of storing a mapping schema which maps a schema for the database management system into a schema for the object oriented environment, and wherein the step of generating one or more application objects comprises the step of examining the mapping schema to determine attributes which are base attributes and which require dereferencing, the step of examining being performed in response to receiving the object query.

33. The program storage device of claim 32, wherein the database management system is a relational database management system.

34. The program storage device of claim 33, wherein each intermediate object includes a foreign key pointer field for each of the foreign keys included in a relational table which maps to a class corresponding to said one or more application objects.