名稱
ST_DumpPoints — 傳回幾何圖形中座標的 geometry_dump 列集合。
概要
geometry_dump[] ST_DumpPoints(geometry geom);
描述
一個集合回傳函數 (SRF)，可提取幾何圖形的座標（頂點）。它傳回一組 geometry_dump 列，每列包含一個幾何圖形（geom 欄位）和一個整數陣列（path 欄位）。
-
geom欄位的POINT代表所提供幾何圖形的座標。 -
path欄位（一個integer[]）是一個索引，列舉所提供幾何圖形元素中的座標位置。索引從 1 開始。例如，對於LINESTRING，路徑為{i}，其中i是LINESTRING中的第nth個座標。對於POLYGON，路徑為{i,j}，其中i是環的編號（1 是外部環；內部環隨後），而j是環中的座標位置。
要取得包含座標的單個幾何圖形，請使用 ST_Points。
增強功能：2.1.0 速度更快。重新實作為原生 C。
增強功能：2.0.0 引入了對多面體表面、三角形和 TIN 的支援。
可用性：1.5.0
這個方法支援圓弧字串和曲線。
此函數支援多面體表面。
此函數支援三角形和三角不規則網路表面 (TIN)。
此函數支援 3d 且不會捨棄 z 索引。
經典範例：將線字串表格展開為節點
SELECT edge_id, (dp).path[1] As index, ST_AsText((dp).geom) As wktnode
FROM (SELECT 1 As edge_id
, ST_DumpPoints(ST_GeomFromText('LINESTRING(1 2, 3 4, 10 10)')) AS dp
UNION ALL
SELECT 2 As edge_id
, ST_DumpPoints(ST_GeomFromText('LINESTRING(3 5, 5 6, 9 10)')) AS dp
) As foo;
edge_id | index | wktnode
---------+-------+--------------
1 | 1 | POINT(1 2)
1 | 2 | POINT(3 4)
1 | 3 | POINT(10 10)
2 | 1 | POINT(3 5)
2 | 2 | POINT(5 6)
2 | 3 | POINT(9 10)
標準幾何範例
SELECT path, ST_AsText(geom)
FROM (
SELECT (ST_DumpPoints(g.geom)).*
FROM
(SELECT
'GEOMETRYCOLLECTION(
POINT ( 0 1 ),
LINESTRING ( 0 3, 3 4 ),
POLYGON (( 2 0, 2 3, 0 2, 2 0 )),
POLYGON (( 3 0, 3 3, 6 3, 6 0, 3 0 ),
( 5 1, 4 2, 5 2, 5 1 )),
MULTIPOLYGON (
(( 0 5, 0 8, 4 8, 4 5, 0 5 ),
( 1 6, 3 6, 2 7, 1 6 )),
(( 5 4, 5 8, 6 7, 5 4 ))
)
)'::geometry AS geom
) AS g
) j;
path | st_astext
-----------+------------
{1,1} | POINT(0 1)
{2,1} | POINT(0 3)
{2,2} | POINT(3 4)
{3,1,1} | POINT(2 0)
{3,1,2} | POINT(2 3)
{3,1,3} | POINT(0 2)
{3,1,4} | POINT(2 0)
{4,1,1} | POINT(3 0)
{4,1,2} | POINT(3 3)
{4,1,3} | POINT(6 3)
{4,1,4} | POINT(6 0)
{4,1,5} | POINT(3 0)
{4,2,1} | POINT(5 1)
{4,2,2} | POINT(4 2)
{4,2,3} | POINT(5 2)
{4,2,4} | POINT(5 1)
{5,1,1,1} | POINT(0 5)
{5,1,1,2} | POINT(0 8)
{5,1,1,3} | POINT(4 8)
{5,1,1,4} | POINT(4 5)
{5,1,1,5} | POINT(0 5)
{5,1,2,1} | POINT(1 6)
{5,1,2,2} | POINT(3 6)
{5,1,2,3} | POINT(2 7)
{5,1,2,4} | POINT(1 6)
{5,2,1,1} | POINT(5 4)
{5,2,1,2} | POINT(5 8)
{5,2,1,3} | POINT(6 7)
{5,2,1,4} | POINT(5 4)
(29 rows)
多面體表面、TIN 和三角形範例
-- Polyhedral surface cube --
SELECT (g.gdump).path, ST_AsEWKT((g.gdump).geom) as wkt
FROM
(SELECT
ST_DumpPoints(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )') ) AS gdump
) AS g;
-- result --
path | wkt
---------+--------------
{1,1,1} | POINT(0 0 0)
{1,1,2} | POINT(0 0 1)
{1,1,3} | POINT(0 1 1)
{1,1,4} | POINT(0 1 0)
{1,1,5} | POINT(0 0 0)
{2,1,1} | POINT(0 0 0)
{2,1,2} | POINT(0 1 0)
{2,1,3} | POINT(1 1 0)
{2,1,4} | POINT(1 0 0)
{2,1,5} | POINT(0 0 0)
{3,1,1} | POINT(0 0 0)
{3,1,2} | POINT(1 0 0)
{3,1,3} | POINT(1 0 1)
{3,1,4} | POINT(0 0 1)
{3,1,5} | POINT(0 0 0)
{4,1,1} | POINT(1 1 0)
{4,1,2} | POINT(1 1 1)
{4,1,3} | POINT(1 0 1)
{4,1,4} | POINT(1 0 0)
{4,1,5} | POINT(1 1 0)
{5,1,1} | POINT(0 1 0)
{5,1,2} | POINT(0 1 1)
{5,1,3} | POINT(1 1 1)
{5,1,4} | POINT(1 1 0)
{5,1,5} | POINT(0 1 0)
{6,1,1} | POINT(0 0 1)
{6,1,2} | POINT(1 0 1)
{6,1,3} | POINT(1 1 1)
{6,1,4} | POINT(0 1 1)
{6,1,5} | POINT(0 0 1)
(30 rows)
-- Triangle --
SELECT (g.gdump).path, ST_AsText((g.gdump).geom) as wkt
FROM
(SELECT
ST_DumpPoints( ST_GeomFromEWKT('TRIANGLE ((
0 0,
0 9,
9 0,
0 0
))') ) AS gdump
) AS g;
-- result --
path | wkt
------+------------
{1} | POINT(0 0)
{2} | POINT(0 9)
{3} | POINT(9 0)
{4} | POINT(0 0)
-- TIN --
SELECT (g.gdump).path, ST_AsEWKT((g.gdump).geom) as wkt
FROM
(SELECT
ST_DumpPoints( ST_GeomFromEWKT('TIN (((
0 0 0,
0 0 1,
0 1 0,
0 0 0
)), ((
0 0 0,
0 1 0,
1 1 0,
0 0 0
))
)') ) AS gdump
) AS g;
-- result --
path | wkt
---------+--------------
{1,1,1} | POINT(0 0 0)
{1,1,2} | POINT(0 0 1)
{1,1,3} | POINT(0 1 0)
{1,1,4} | POINT(0 0 0)
{2,1,1} | POINT(0 0 0)
{2,1,2} | POINT(0 1 0)
{2,1,3} | POINT(1 1 0)
{2,1,4} | POINT(0 0 0)
(8 rows)