描述

<#> 运算符返回两个浮点边界框之间的距离，可能从空间索引中读取（需要 PostgreSQL 9.1+）。对于执行最近邻 近似 距离排序很有用。

	此操作数将利用几何体上可能存在的任何索引。它与使用空间索引的其他运算符不同，因为空间索引仅在运算符位于 ORDER BY 子句中时使用。

	索引仅在其中一个几何体是常量时才生效，例如 ORDER BY (ST_GeomFromText('POINT(1 2)') <#> geom) 而不是 g1.geom <#>。

可用性：2.0.0 -- KNN 仅适用于 PostgreSQL 9.1+

示例

SELECT *
FROM (
SELECT b.tlid, b.mtfcc,
	b.geom <#> ST_GeomFromText('LINESTRING(746149 2948672,745954 2948576,
		745787 2948499,745740 2948468,745712 2948438,
		745690 2948384,745677 2948319)',2249) As b_dist,
		ST_Distance(b.geom, ST_GeomFromText('LINESTRING(746149 2948672,745954 2948576,
		745787 2948499,745740 2948468,745712 2948438,
		745690 2948384,745677 2948319)',2249)) As act_dist
    FROM bos_roads As b
    ORDER BY b_dist, b.tlid
    LIMIT 100) As foo
    ORDER BY act_dist, tlid LIMIT 10;

   tlid    | mtfcc |      b_dist      |     act_dist
-----------+-------+------------------+------------------
  85732027 | S1400 |                0 |                0
  85732029 | S1400 |                0 |                0
  85732031 | S1400 |                0 |                0
  85734335 | S1400 |                0 |                0
  85736037 | S1400 |                0 |                0
 624683742 | S1400 |                0 | 128.528874268666
  85719343 | S1400 | 260.839270432962 | 260.839270432962
  85741826 | S1400 | 164.759294123275 | 260.839270432962
  85732032 | S1400 |           277.75 | 311.830282365264
  85735592 | S1400 |           222.25 | 311.830282365264
(10 rows)

另请参阅

ST_DWithin, ST_Distance, <->