有效使用EnvelopeAggregate [英] Efficient use of EnvelopeAggregate

问题描述

你好！ 

我需要计算大型多边形表的边界框。即包含表中所有几何的聚合边界框。多边形存储在表中的
几何列中，该列已编制索引。 我是否可以使用列上的空间索引来执行此操作？

我试过Geometry :: EnvelopeAggregate （）。它似乎是使用顺序扫描，而不是使用索引。这可能是它的实现方式，但我在这里发布
，希望我错过了什么。我想要的是类似于min（）和max（）聚合函数在索引列上运行得更快。或者类似的包络函数在基于R树的空间索引实现上工作得更快。

如果多边形存储在地理列中，您的答案会不同吗？

对于Geometry类型，我知道我可以查询边界索引是使用这样的查询创建的，但这会返回创建
索引的边界框，而不是'true'聚合包络。

< p style =""> 选择b.name，
  &NBSP;&NBSP; a.bounding_box_xmin，bounding_box_ymin，bounding_box_xmax，bounding_box_ymax

     
来自sys.spatial_index_tessellations a，sys.spatial_indexes b

     
其中b.object_id = a.object_id和b.name喜欢< index_name> ;;

感谢您的帮助。

Anand。

解决方案

Hi
Anand，

 

请参考博客和类似问题。

 

问题：
https://stackoverflow.com/questions/16410757/bounding-box-for-polygon

 

博客：
https://alastaira.wordpress.com/2011/07/26/determining-the-geographic-extent-of-spatial-features-in-a-sql-server-table /

 

最好的问候，

艾米丽

Hi there! 

I need to compute the bounding box of a large table of polygons. i.e. the aggregate bounding box that encloses all geometries in the table. The polygons are stored in a Geometry column in a table, which is indexed. Is there a way for me to do this using the spatial index on the column?

I tried Geometry::EnvelopeAggregate(). It appears to be using a sequential scan, rather than use the index. That may be how it is implemented, but I am posting here, hoping I missed something. What I want is analogous to min() and max() aggregate functions working faster on an indexed column. Or comparable envelope functions working faster on R-tree based spatial index implementations.

Will your answer be different if the polygons were stored in a Geography column?

For the Geometry type, I know I can query the bounds that the index was created with using a query like this, but this returns the bounding box the index was created with, rather than the ‘true’ aggregate envelope.

select b.name,     a.bounding_box_xmin, bounding_box_ymin, bounding_box_xmax, bounding_box_ymax

      from sys.spatial_index_tessellations a, sys.spatial_indexes b

      where b.object_id = a.object_id and b.name like <index_name>;

Thanks for your help.

Anand.

解决方案

Hi Anand,

 

Please refer to the blog and the similar question.

 

Question: https://stackoverflow.com/questions/16410757/bounding-box-for-polygon

 

Blog: https://alastaira.wordpress.com/2011/07/26/determining-the-geographic-extent-of-spatial-features-in-a-sql-server-table/

 

Best Regards,

Emily

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