Effectively and efficiently supporting XML sequence type and XQuery sequence natively in a SQL system

• US 20060224576A1
• Filed: 04/04/2005
• Published: 10/05/2006
• Est. Priority Date: 04/04/2005
• Status: Active Grant

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: Oracle International Corporation (Oracle Corporation)
• Inventors: Warner, James W., Krishnaprasad, Muralidhar, Liu, Zhen Hua
• Granted Patent: US 8,463,801 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 16/86 Mapping to a database

Abstract

Techniques for effectively and efficiently supporting XML sequence type and XQuery sequence natively in a SQL system are described. According to one aspect, SQL functions that correctly handle XML sequences are provided. Thus, XML sequences are handled effectively. According to another aspect, rules for simplifying an abstract syntax tree (AST) that represents one or more such SQL functions are provided. For each such SQL function that is represented in an AST that represents a SQL query, one or more rules that are relevant to that SQL function are determined. Relevant rules are applied to the representation of the SQL function within the AST. Through the application of the rules to the representations of the SQL functions within the AST, the AST is modified in a manner that simplifies the AST prior to the evaluation of the AST at query execution time. Thus, XML sequences are handled efficiently.

Claims

1. A method of processing a Structured Query Language (SQL) query containing an invocation of XQuery, comprising:

processing a query that contains at least one SQL function that either (a) has an input parameter that is of Extensible Markup Language (XML) sequence type or (b) has an output parameter that is of XML sequence type; and

evaluating the SQL function.

2. The method of claim 1, wherein an input parameter of the SQL function is a SQL scalar value, wherein an output parameter of the SQL function is an instance that (a) is of XML sequence type and (b) is a sequence of an XQuery atomic value, and wherein the SQL scalar value is equal to the XQuery atomic value.

3. The method of claim 1, wherein an output parameter of the SQL function is a SQL scalar value, wherein an input parameter of the SQL function is an instance that (a) is of XML sequence type and (b) is a sequence of one XQuery atomic value, and wherein the SQL scalar value is equal to the XQuery atomic value.

4. The method of claim 1, wherein a first input parameter of the SQL function is a first integer, wherein a second input parameter of the SQL function is a second integer, wherein an output parameter of the SQL function is an instance that (a) is of XML sequence type and (b) is a sequence of XQuery integer atomic values, wherein the first XQuery integer atomic value in the sequence is equal to the first integer, wherein the last XQuery integer atomic value in the sequence is equal to the second integer, and wherein the XQuery atomic values that occur between the first XQuery atomic value and the last XQuery atomic value in the sequence are respectively equal to the integers that exist, in the integer domain, between the first integer and the second integer.

5. The method of claim 1, wherein an input parameter of the SQL function is a first instance that (a) is of XML sequence type and (b) is a sequence of items, wherein an output parameter of the SQL function is a second instance that is of XML content type, and wherein for each particular item in the sequence of items, the second instance contains a separate node that corresponds to the particular item.

6. The method of claim 1, wherein an output parameter of the SQL function is a first instance that (a) is of XML sequence type and (b) is a sequence of items, wherein an input parameter of the SQL function is a second instance that is of XML content type, and wherein for each particular item in the sequence of items, the second instance contains a separate node that corresponds to the particular item.

7. The method of claim 1, wherein an output parameter of the SQL function is an instance that (a) is of XML sequence type and (b) is a sequence of items, and wherein for each particular input parameter in a set of two or more input parameters of the SQL function, the ordered collection contains a separate item that corresponds to the particular input parameter.

8. The method of claim 1, wherein an output parameter of the SQL function is a first instance that (a) is of XML sequence type and (b) is a sequence of items, wherein an input parameter of the SQL function is a SQL collection of XMLType instances, and wherein for each particular XMLType(content) or XMLType(document) instance in the input SQL collection of instances, the output sequence contains a separate item that corresponds to the particular instance, and wherein for each particular XMLType(sequence) instance in the input SQL collection, the output sequence contains all items that contained in that XMLType(sequence) instance.

9. The method of claim 1, wherein an input parameter of the SQL function is a first instance that (a) is of XML sequence type and (b) is a sequence of items, wherein an output parameter of the SQL function is a SQL collection of XMLType instances, wherein each XMLType instance in the output SQL collection of instances is of XML sequence type, and wherein for each particular item in the input sequence of items, the output SQL collection contains a separate instance that corresponds to the particular item.

10. The method of claim 1, wherein a first input parameter of the SQL function is an object that (a) is of XML sequence type and (b) is a first sequence of items, wherein a second input parameter of the SQL function is an XPath expression, wherein an output parameter of the SQL function is an instance that (a) is of XML sequence type and (b) is a second sequence of items, and wherein for each particular node that (a) is represented within the first sequence of items and (b) occurs hierarchically at a location indicated by the XPath expression, the second sequence of items contains a separate item that corresponds to the particular node.

11. The method of claim 1, wherein an input parameter of the SQL function is a first object that (a) is of XML sequence type and (b) is a sequence of a first node, wherein an output parameter of the SQL function is a second object that is of XML content type, and wherein the second object contains a second node that is a text value of the first node.

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 1.

12. A method of simplifying an abstract syntax tree that represents a query, comprising:

determining whether the abstract syntax tree includes a representation of a first Structured Query Language (SQL) function that either (a) has an input parameter that is of Extensible Markup Language (XML) sequence type or (b) has an output parameter that is of XML sequence type; and

in response to a determination that the abstract syntax tree includes the representation, determining one or more rules that apply to the first SQL function; and

prior to evaluating the abstract syntax tree to execute the query, modifying the abstract syntax tree by applying the one or more rules to the first SQL function in the abstract syntax tree.

13. The method of claim 12, wherein determining the one or more rules that apply to the first SQL function comprises:

determining whether an input parameter of the first SQL function is a null value;

determining whether the first SQL function is a member of a specified set of SQL functions; and

in response to a determination that (a) an input parameter of the first SQL function is a null value and (b) the first SQL function is a member of the specified set of SQL functions, including, within the one or more rules, a rule which, when applied, replaces the first SQL function with a null value.

14. The method of claim 12, wherein determining the one or more rules that apply to the first SQL function comprises:

determining whether an input parameter of the first SQL function is a SQL CASE expression;

determining whether the first SQL function is a member of a specified set of SQL functions; and

in response to a determination that (a) an input parameter of the first SQL function is a SQL CASE expression and (b) the first SQL function is a member of the specified set of SQL functions, including, within the one or more rules, a rule which, when applied, replaces the first SQL function with a SQL CASE expression that contains the first SQL function as a return expression.

15. The method of claim 12, wherein determining the one or more rules that apply to the first SQL function comprises:

determining whether an input parameter of the first SQL function is a SQL subquery;

determining whether the first SQL function is a member of a specified set of SQL functions; and

in response to a determination that (a) an input parameter of the first SQL function is a SQL subquery and (b) the first SQL function is a member of the specified set of SQL functions, including, within the one or more rules, a rule which, when applied, replaces the first SQL function with a SQL query that contains the first SQL function in a select list of the SQL query.

16. The method of claim 12, wherein determining the one or more rules that apply to the first SQL function comprises:

determining whether the first SQL function converts an input parameter that is of XML sequence type into an output parameter that is a SQL scalar value;

determining whether an input parameter of the first SQL function is a second SQL function that converts an input parameter that is a particular SQL scalar value into an output parameter that is of XML sequence type; and

in response to a determination that (a) the first SQL function converts an input parameter that is of XML sequence type into an output parameter that is a SQL scalar value and (b) the second SQL function is an input parameter of the first SQL function, including, within the one or more rules, a rule which, when applied, replaces the first SQL function with the particular SQL scalar value.

17. The method of claim 12, wherein determining the one or more rules that apply to the first SQL function comprises:

determining whether the first SQL function has (a) a first input parameter that is a first integer, (b) a second input parameter that is a second integer, and (c) an output parameter that is an XML sequence of atomic values that represent all integers between and including the first integer and the second integer;

determining whether the first integer is equal to the second integer; and

in response to a determination that (a) the first SQL function has (i) a first input parameter that is a first integer, (ii) a second input parameter that is a second integer, and (iii) an output parameter that is an XML sequence of atomic values that represent all integers between and including the first integer and the second integer, and (b) the first integer is equal to the second integer, including, within the one or more rules, a rule which, when applied, replaces the first SQL function with the first integer.

18. The method of claim 12, wherein determining the one or more rules that apply to the first SQL function comprises:

determining whether the first SQL function converts an input parameter that is an instance of XML sequence type into an output parameter that is an instance of XML content type;

determining whether an input parameter of the first SQL function is a second SQL function that converts an input parameter that is a particular instance of XML content type into an output parameter that is an instance of XML sequence type;

determining whether a subtype of the particular instance is contained within a set of specified subtypes of XML content type; and

in response to a determination that (a) the first SQL function converts an input parameter that is an instance of XML sequence type into an output parameter that is an instance of XML content type, (b) the second SQL function is an input parameter of the first SQL function, and (c) the subtype is contained within the set of specified subtypes, including, within the one or more rules, a rule

which, when applied, replaces the first SQL function with an input parameter of the second SQL function.

19. The method of claim 12, wherein determining the one or more rules that apply to the first SQL function comprises:

determining whether the first SQL function converts an input parameter that is an instance of XML content type into an output parameter that is an instance of XML sequence type;

determining whether an input parameter of the first SQL function is a second SQL function that converts an input parameter that is a particular instance of XML sequence type into an output parameter that is an instance of XML content type;

determining whether a subtype of the particular object is contained within a set of specified subtypes of XML sequence type; and

in response to a determination that (a) the first SQL function converts an input parameter that is an instance of XML content type into an output parameter that is an instance of XML sequence type, (b) the second SQL function is an input parameter of the first SQL function, and (c) the subtype is contained within the set of specified subtypes, including, within the one or more rules, a rule which, when applied, replaces the first SQL function with an input parameter of the second SQL function.

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 12.