Spatial Distance Semi-Join Based on Multi-Approximate Spatial Index
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摘要: 为了更有效地解决基于外部近似索引空间距离半连接效率较低问题,提出一种基于多重近似索引的空间距离半连接处理方法.该方法在充分利用多重近似索引结构特征基础上,推导出在半连接处理中的距离和空间对象数量约束关系,并在距离半连接算法中利用这些约束关系进行连接处理,从而减少了进行精过滤处理空间对象的数量.通过实验分析表明,基于多重近似索引的距离半连接算法有效,并且基于多重近似索引比基于外部近似索引的距离半连接效率要高.Abstract: To improve the efficiency for space distance semi-join based on external approximation index, a method of spatial distance semi-join based on multi-approximate index is proposed. The constraint relationship of distance and the number of spatial objects during processing semi-join are deduced based on taking advantage of characteristics of multi-approximate index structure. And these are used during spatial distance semi-join to reduce the number of spatial objects needed to process during refine filter step. A series of tests and verifications indicate that the new method of spatial distance semi-join is valid and the performance of index based on multi-approximation is more effective than the index based on external approximation during processing spatial distance semi-join.
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Key words:
- semi-join /
- spatial distance /
- spatial index /
- multi-approximate index /
- spatial database
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表 1 不同距离上限和索引结构下距离半连接性能比较
Table 1. The performance comparison of distance semi-join by the difference distance upper-limit and index structure
距离上限 距离计算次数(次) 需精过滤对象对数(对) R-tree MR-tree R-tree MR-tree 100 8 380 18 844 84 54 200 13 754 32 027 141 90 400 26 036 61 940 228 119 600 41 188 99 088 239 137 800 58 382 141 635 312 171 1 000 77 438 189 170 326 178 1 300 97 344 238 935 276 178 1 500 102 026 250 640 183 104 1 700 102 950 252 950 43 32 2 000 102 950 252 950 0 0 表 2 不同连接结果k和索引结构下距离半连接性能比较
Table 2. The performance comparison of distance semi-join by the difference join result k and index structure
k 距离计算次数(次) 需精过滤对象对数(对) R-tree MR-tree R-tree MR-tree 1 16 692 39 060 3 2 2 16 692 39 060 3 2 3 16 692 39 060 3 2 4 16 692 39 060 3 2 5 16 692 39 060 3 2 6 16 692 39 060 5 3 7 19 124 45 140 6 4 8 19 124 45 140 13 8 9 19 124 45 140 22 13 10 21 322 50 635 30 17 11 21 322 50 635 37 18 12 21 322 50 635 41 19 13 21 322 50 635 47 20 14 21 322 50 635 51 23 15 21 322 50 635 56 25 16 21 642 50 955 61 27 17 21 642 50 955 62 28 18 22 992 54 330 68 32 19 22 992 54 330 77 37 20 22 992 54 330 81 40 -
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