Immutable Bookmarks for Large Objects in a Database

• US 20070299816A1
• Filed: 06/27/2006
• Published: 12/27/2007
• Est. Priority Date: 06/27/2006
• Status: Active Grant

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: Oracle International Corporation (Oracle Corporation)
• Inventors: Krishnaprasad, Muralidhar, Arora, Geeta
• Granted Patent: US 7,630,957 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 16/2219 Large Object storage; Management thereof
• CPC Class Codes: Y10S 707/99932 Access augmentation or optimizing

Abstract

User-level bookmarks are initially created at a specified offset in a large object (LOB) of a database and automatically updated to reflect a new offset, if necessary, after database updates. By logically linking the bookmark to a data element, the bookmark continues to point to the same logical data element as it did before the update. An API provides the functionality of immutable bookmarks by automatically changing the offset of the bookmark following sliding inserts or deletions of data to the database.

Claims

1. In a database that utilizes bookmarks to access user selected data stored in a database, a method for maintaining the association between the bookmarks and the user selected data comprising:

associating a bookmark with an offset;

reorganizing the database such that the user selected data is stored at an updated offset; and

associating the bookmark with the updated offset.

2. The method of claim 1 further comprising automatically maintaining association between the bookmark and the updated offset whereby the bookmark is immutable when viewed.

3. The method of claim 1 further comprising updating an offset associated with the bookmark to match the offset associated with the user selected data.

4. The method of claim 3 wherein updating the offset associated with the bookmark comprises updating an entry in bookmark dictionary when reorganizing the database.

5. The method of claim 4 wherein updating the entry in the bookmark dictionary comprises updating a page in a LOB.

6. The method of claim 4 wherein updating the entry in the bookmark dictionary comprises updating a table not visible to a user.

7. The method of claim 3 wherein updating the offset associated with the bookmark comprises updating a hash table.

8. The method of claim 3 wherein updating the offset associated with the bookmark comprises associating an offset with the bookmark in accordance with (p−

x+y), where p denotes an initial offset, x denotes the number of deleted bytes, and y denotes the number of inserted bytes between the start of the LOB and the offset associated with the bookmark.

9. The method of claim 1 wherein user selected data stored in the database comprises a LOB.

11. The method of claim 1 wherein user selected data stored in the database comprises a BLOB.

12. The method of claim 11 further comprising updating the offset associated with the bookmark to match a binary offset associated with the user selected data in the BLOB.

13. The method of claim 1 wherein user selected data stored in the database comprises a CLOB.

14. The method of claim 13 further comprising updating the offset associated with the bookmark to match the character offset associated with the user selected data.

15. The method of claim 1 wherein user selected data stored in the database comprises a large varchar.

16. The method of claim 1 further comprising defining a relative bookmark having an offset relative to the bookmark associated with the user selected data.

17. The method of claim 1 further comprising removing the bookmark when a range of data that includes the user selected data is deleted from the database.

10. The method of claim 10 further comprising updating the offset associated with the bookmark to match a binary offset associated with the user selected data in the LOB.

18. In a relational database having a plurality of large datatypes and a plurality of bookmarks, each of which point to user selected data stored at a specific offset within the database, a system for updating at least one of the bookmarks in response to a database reorganization, the system comprising:

means for storing the database;

means, coupled to the storing means and operating on a server, for managing the database; and

an application program interface, coupled to the managing means, adapted to create a bookmark logically linked to user selected data stored in one of the plurality of large datatypes and to associate an offset with the bookmark.

19. The system of claim 18 wherein the application program interface further comprises means for changing the offset associated with the bookmark during database reorganization.

20. The system of claim 18 wherein the application program interface further comprises means for calculating a new offset associated with the bookmark to maintain a logical linkage with user selected data after reorganization of the database.

21. The system of claim 20 wherein the database reorganization comprises the insertion of additional bytes.

22. The system of claim 21 wherein the database reorganization comprises the deletion of bytes.

23. The system of claim 18 wherein the application program interface further comprises means for changing the offset associated with the bookmark during database update in accordance with (p−

x+y), where p denotes an initial offset, x denotes the number of deleted bytes, and y denotes the number of inserted bytes between the start of the LOB and the offset associated with the bookmark

24. The system of claim 18 wherein the application program interface further comprises a hash table for changing the offset associated with the bookmark during database update.

25. The system of claim 18 wherein the application program interface further comprises a bookmark dictionary for maintaining the offset associated with the bookmark to maintain the logical linkage with the user selected data following update of the database.

26. The system of claim 18 wherein the application program interface further comprises a plurality of bookmark dictionaries for maintaining the offset associated with a plurality of bookmark to maintain the logical linkage between each of the plurality of bookmarks with the user selected data during database update, each of said plurality of bookmark dictionaries associated with one of a plurality of LOBs.

27. A method for adding bookmarks to a relational database having a plurality of large objects (LOBs), the method comprising:

defining a bookmark by associating the bookmark at an initial offset in a LOB;

in response to a database reorganization, calculating an updated offset for the bookmark; and

updating the initial offset associated with the bookmark to reflect the updated offset.

28. The method of claim 27 further comprising logically linking the bookmark with user specified data.

29. The method of claim 28 wherein the user specified data comprises an Extensible Markup Language (XML) document.

30. The method of claim 27 wherein the bookmark is immutable.

31. A machine-readable medium including instructions executable by one or more processors, the machine-readable medium comprising:

one or more instructions for defining a bookmark by associating the bookmark at an initial offset in a database;

one or more instructions for calculating an updated offset for the bookmark; and

one or more instructions for updating the initial offset associated with the bookmark to reflect the updated offset.

32. An information storage medium having a plurality of instructions adapted to direct an information processing device to perform a set of steps including:

defining an immutable bookmark by associating the bookmark with data stored at a location in a database;

updating the database such that the data is stored at an updated location in the database; and

associating the bookmark with the updated location.

33. The information storage medium of claim 32, wherein the bookmark association comprises associating the bookmark with an offset in a large object (LOB).

34. The information storage medium of claim 32, wherein the bookmark association comprises associating the bookmark with an offset in a character large object (CLOB).

35. The information storage medium of claim 32 having a plurality of instructions further adapted to updating the offset associated with the bookmark, said adapting comprising updating an entry in bookmark dictionary.