XQuery连接图隔离
XQuery Join Graph Isolation
摘要：
真正的XQuery语义的纯关系解释可以将任何关系数据库系统转变为XQuery处理器。然而，编译完全组合的XQuery语言的嵌套表达式会产生奇怪的代数计划形状，其特点是连接运算符的分散分布，目前商业SQL查询优化器无法解决这些问题。此工作在提交到关系数据库后端之前重写此类计划。一旦转换成连接图的形状，我们已经找到了现成的关系查询优化器-特别是B树索引子系统和连接树规划器-来应对甚至能够自主地“重新发明”最初专门为XQuery领域设计的高级处理策略，例如，单步重排序、轴反转和路径缝合。性能评估提供的证据表明，关系查询引擎是当今最通用、最高效的XQuery处理器之一。
英文摘要：
A purely relational account of the true XQuery semantics can turn any relational database system into an XQuery processor. Compiling nested expressions of the fully compositional XQuery language, however, yields odd algebraic plan shapes featuring scattered distributions of join operators that currently overwhelm commercial SQL query optimizers. This work rewrites such plans before submission to the relational database back-end. Once cast into the shape of join graphs, we have found off-the-shelf relational query optimizers--the B-tree indexing subsystem and join tree planner, in particular--to cope and even be autonomously capable of "reinventing" advanced processing strategies that have originally been devised specifically for the XQuery domain, e.g., XPath step reordering, axis reversal, and path stitching. Performance assessments provide evidence that relational query engines are among the most versatile and efficient XQuery processors readily available today.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
