7、高效结构连接与非谓词的基于路径的方法及结果率渐进连接算法

高效结构连接与非谓词的基于路径的方法及结果率渐进连接算法

在数据处理和查询领域，高效的算法对于处理复杂的查询和数据流至关重要。本文将介绍两种重要的算法：基于路径的结构连接算法和结果率渐进连接算法（RRPJ），并探讨它们的原理、优势和实验评估。

基于路径的结构连接算法

算法 PJoin¬

PJoin¬ 算法用于处理带有非谓词的结构连接查询，其输入为一个 XQuery 树，输出为树中节点的路径 ID。以下是该算法的详细步骤：

Algorithm 1. PJoin¬
1: Input: T - An XQuery-tree
2: Output: Path ids for the nodes in T
3: Associate every node in T with its path ids;
4: Perform a bottom-up binary path join on T b
P and T a
P ;
5: Perform a top-down binary path join on T b
P and T a
P ;
6: Perform a path anti-join between the root node(s) of T b
P and their parent node(s)
if necessary;
7: Perform a bottom-up binary path join on TP;
8: Perform a path anti-join between the leaf node of T a
P with its child node if necess