Efficient extraction of XML content stored in a LOB

• US 20050228828A1
• Filed: 02/15/2005
• Published: 10/13/2005
• Est. Priority Date: 04/09/2004
• Status: Active Grant

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: Oracle International Corporation (Oracle Corporation)
• Inventors: Sedlar, Eric, Thusoo, Ashish, Chandrasekar, Sivasankaran, Murthy, Ravi, Agarwal, Nipun, Mukkamalla, Sreedhar
• Granted Patent: US 7,366,735 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 16/81 Indexing, e.g. XML tags; Data structures therefor; Storage structures
• CPC Class Codes: G06F 16/835 Query processing
• CPC Class Codes: G06F 16/84 Mapping; Conversion
• CPC Class Codes: Y10S 707/99942 Manipulating data structure, e.g. compression, compaction, compilation
• CPC Class Codes: Y10S 707/99943 Generating database or data structure, e.g. via user interface
• CPC Class Codes: Y10S 707/99945 Object-oriented database structure processing
• CPC Class Codes: Y10S 707/99948 Application of database or data structure, e.g. distributed, multimedia, or image

Abstract

A method and system are provided for extracting a valid, self-contained fragment for a node in a XML document stored in a database management system. An XML index is used to identify a location in which XML fragment data corresponding to the node is located. Ancestors of the node are identified and examined for any information needed for the proper interpretation of the fragment. If an ancestor node contains such needed information, this information is patched into the XML fragment to ensure that the fragment is a valid, self-contained XML fragment.

Claims

1. A method for providing a self-contained XML fragment for a node in an XML document managed by a database management system, the method comprising the computer-implemented steps of:

receiving a request for an XML fragment, wherein the request includes an XML path expression;

identifying a node, in an XML document managed by the database management system, that matches the XML path expression;

extracting a first XML fragment corresponding to the identified node;

identifying ancestor nodes for the identified node;

for each identified ancestor node, determining if the ancestor node includes information needed for proper interpretation of the first XML fragment, and if the ancestor node does include needed information, inserting a second XML fragment containing the needed information into the first XML fragment; and

providing the first XML fragment in response to the request.

2. The method of claim 1 wherein the database management system includes an index that indexes the XML documents stored in the database management system, and wherein the step of identifying a node in an XML document comprises using the index to identify the node.

3. The method of claim 2 wherein the index includes path, value and order indexes.

4. The method of claim 1 wherein the step of extracting a first XML fragment includes:

determining a location of stored XML data corresponding to the identified node; and

reading XML data from the determined location.

5. The method of claim 4 wherein the step of determining a location of stored XML data corresponding to the identified node includes reading location information from an index that indexes the XML documents stored in the database management system.

6. The method of claim 2 wherein the step of extracting a first XML fragment includes:

constructing an XML fragment using information in the index.

7. The method of claim 3, wherein the step of identifying ancestor nodes includes using the order index.

8. The method of claim 1 wherein the information needed for proper interpretation of the first XML fragment is a namespace declaration.

9. The method of claim 8 wherein the step of determining if the ancestor node includes information needed for proper interpretation includes determining if the namespace declaration was declared in a previously considered ancestor node.

10. The method of claim 8 wherein the step of determining if the ancestor node includes information needed for proper interpretation includes determining if the namespace declaration was declared in first XML fragment.

11. The method of claim 1 wherein the step of determining if an ancestor node includes information needed for proper interpretation is performed for each ancestor node in order from a closest ancestor node to a root ancestor node.

12. The method of claim 11 wherein the information needed for proper interpretation of the first XML fragment is a namespace declaration, and if a namespace declaration in an ancestor node matches a namespace declaration in ancestor node already considered, it is determined that the namespace declaration is not needed for proper interpretation.

13. A computer-readable medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 1.

14. A computer-readable medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 2.

15. A computer-readable medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 3.

16. A computer-readable medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 4.

17. A computer-readable medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 5.

18. A computer-readable medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 6.

19. A computer-readable medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 7.

20. A computer-readable medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 8.

21. A computer-readable medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 9.

22. A computer-readable medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 10.

23. A computer-readable medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 11.

24. A computer-readable medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 12.

25. A method comprising the computer-implemented steps of:

receiving a request for an XML fragment, wherein the request includes an XML path expression;

within a database management system, using an index to identify a node that matches the XML path expression;

wherein the node resides in an XML document managed by the database management system;

wherein the XML document is stored within one or more base structures managed by the database management system;

determining whether the node is for a simple element; and

if the node is for a simple element, then performing the steps of constructing the XML fragment for the node based on information contained in the index without accessing the one or more base structures; and

providing the XML fragment in response to the request.

26. A computer -readable medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 25.