Interleaving XML Index Rewrites and View Merges
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Solution Overview
Problem
Current database systems face inefficiencies in query optimization due to the high computational cost of applying various transformations in all possible combinations, which can outweigh the cost of computing the original query, especially when interleaving XML index rewrites and view merges during query optimization.
Innovation Solution
Interleaving XML index rewrite and view merge transformations in a specific sequence to generate more efficient execution plans, where XML index rewrites follow view merges, allowing for further optimization through additional view merges and XML rewrites, thereby reducing computational costs and improving query efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all possible combinations of query transformations are applied, then query optimization completeness is improved, but computational cost increases significantly
Solution Approach 1:
The patent segments the query transformation process into distinct phases: initial transformations are applied, then XML index rewrites are applied, then additional view merges are applied. This segmentation allows the optimizer to systematically explore transformation combinations without evaluating all possible permutations, thereby reducing computational cost while maintaining optimization effectiveness.
Solution Approach 2:
The patent performs preliminary view merges before applying XML index rewrites. By completing view merges in advance, the subsequent XML index rewrite operations can work with pre-optimized query structures, reducing the overall computational burden and avoiding redundant transformation operations.
2Productivity
If XML index rewrites and view merges are applied in all combinations, then query execution efficiency is improved, but optimization time increases
Solution Approach 1:
The optimization process is segmented into sequential stages: first view merges are applied to eliminate inline views, then XML index rewrites are applied to rewrite XML queries against index structures, and finally additional view merges are applied. This staged approach ensures that each transformation type is applied optimally without redundant combinations, reducing optimization time while maintaining execution efficiency.
Solution Approach 2:
View merges are performed as a preliminary action before XML index rewrites. This preliminary view merging reduces the complexity of subsequent XML index rewrite operations by working with simplified query structures, thereby reducing overall optimization time while preserving query execution efficiency.
3Reliability
If multiple transformation sequences are evaluated, then execution plan quality is improved, but computational overhead increases
Solution Approach 1:
The patent segments transformation evaluation into a structured sequence: initial view merges, then XML index rewrites, then additional view merges. This segmentation creates a manageable search space for transformation combinations, allowing the optimizer to evaluate a representative sample of transformation sequences rather than all possible permutations, thereby reducing computational overhead while maintaining execution plan quality.
Solution Approach 2:
The patent performs preliminary view merges before evaluating XML index rewrite options. This preliminary action establishes a foundation of optimized query structures that reduces the computational overhead of subsequent transformation evaluations, as the XML index rewrites can be applied to simpler, pre-optimized query forms.
Data Source
AI summary
During query optimization, XML index and view merge transformations may be interleaved.