XML Query Rewriting via Structured Index Path Fusion
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Solution Overview
Problem
Existing database systems face inefficiencies in querying XML data, particularly when it is stored in aggregate form, as traditional query mechanisms are resource-intensive and time-consuming, and structured XML indexes are often underutilized due to strict matching requirements for path expressions.
Innovation Solution
The solution involves rewriting queries to leverage structured XML indexes by analyzing operator trees, fusing path expressions, and grouping operators to minimize index scans, allowing for indirect matching and using the index as an implied schema to optimize queries that refer to XML data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional query mechanisms are used on XML data stored in aggregate form, then query capability is maintained, but query performance is poor and resource consumption is high
Solution Approach 1:
The patent pre-processes XML data by creating structured indexes that organize XML elements, attributes, and text values into relational table structures before queries are executed. This preliminary organization enables fast query evaluation without requiring resource-intensive parsing during query execution.
Solution Approach 2:
The patent introduces an intermediary structured index layer between the aggregate XML storage and the query processing mechanism. This index acts as a mediator that translates XML queries into efficient relational database operations, avoiding direct parsing of large XML documents during query execution.
2Productivity
If structured XML indexes are created to improve query performance, then query evaluation speed increases, but index creation complexity and storage requirements increase
Solution Approach 1:
The patent segments XML data into discrete components (elements, attributes, text values) and organizes them into separate relational tables. Each table stores specific aspects of the XML structure, allowing independent optimization and management of each segment without handling the entire XML document as a monolithic structure.
Solution Approach 2:
The patent creates a universal indexed structure that can serve multiple query types and purposes. The same index tables support various XML queries including element selection, attribute filtering, and text searching, eliminating the need for separate indexing mechanisms for different query operations.
3Measurement precision
If strict matching requirements are enforced for path expressions to ensure index accuracy, then query result precision is maintained, but query flexibility and adaptability are reduced
Solution Approach 1:
The patent allows partial matches between query path expressions and index structures. Instead of requiring exact matches, the system accepts queries that partially align with indexed paths and uses the available index data where applicable, supplementing with full XML parsing only for the unmatched portions.
Solution Approach 2:
The patent transforms rigid path expression matching into a flexible parameter-based matching system. Query path expressions are converted into parameterized patterns that can match multiple index entries with varying specificity, allowing the same index structure to serve queries with different levels of detail and specificity.
Data Source
AI summary
A query may be rewritten to leverage information stored in a structured XML index. An operator in the query may be analyzed to determine an input source database object for the operator by traversing an operator tree rooted at the operator. The path expressions associated with the operator tree may be fused together to form an effective path expression for the operator. If the effective path expression directly matches a path expression derived from the index, the query may be rewritten using references to the index. Operators in a query that have effective paths that refer to data in the same index table may be grouped together. A single subquery may be written for a group of operators. Also, a structured XML index may be used as an implied schema for indexed XML data. This implied schema may be used to optimize queries that refer to the indexed XML data.