PostGIS returns 记录为数据类型。这是出乎意料的
PostGIS returns record as datatype. This is unexpected
我有这个问题
WITH buffered AS (
SELECT
ST_Buffer(geom , 10, 'endcap=round join=round') AS geom,
id
FROM line),
hexagons AS (
SELECT
ST_HexagonGrid(10, buffered.geom) AS hex,
buffered.id
FROM buffered
) SELECT * FROM hexagons;
这会在 hex
列中给出 datatype
record
。这是出乎意料的。我预计 geometry
为 datatype
。这是为什么?
根据documentation
,函数ST_HexagonGrid
returns一个setof record
。然而,这些记录包含一个名为 geom
的 geometry
属性,因此为了访问此 record
的 geometry
,您必须用括号 ()
和用点 .
调用属性,例如
SELECT (hex).geom FROM hexagons;
或使用 *
访问获取所有属性(在本例中,i
、j
和 geom
):
SELECT (hex).* FROM hexagons;
演示(PostGIS 3.1):
WITH j (hex) AS (
SELECT
ST_HexagonGrid(
10,ST_Buffer('LINESTRING(-105.55 41.11,-115.48 37.16,-109.29 29.38,-98.34 27.13)',1))
)
SELECT ST_AsText((hex).geom,2) FROM j;
st_astext
----------------------------------------------------------------------------------------
POLYGON((-130 34.64,-125 25.98,-115 25.98,-110 34.64,-115 43.3,-125 43.3,-130 34.64))
POLYGON((-115 25.98,-110 17.32,-100 17.32,-95 25.98,-100 34.64,-110 34.64,-115 25.98))
POLYGON((-115 43.3,-110 34.64,-100 34.64,-95 43.3,-100 51.96,-110 51.96,-115 43.3))
POLYGON((-100 34.64,-95 25.98,-85 25.98,-80 34.64,-85 43.3,-95 43.3,-100 34.64))
作为 ST_HexagonGrid
returns a setof record
,您可以使用 LATERAL
访问记录属性,如 here
所述,或者只调用函数FROM
子句:
SELECT i,j,ST_AsText(geom,2) FROM
ST_HexagonGrid(
10,ST_Buffer('LINESTRING(-105.55 41.11,-115.48 37.16,-109.29 29.38,-98.34 27.13)',1));
i | j | st_astext
----+---+----------------------------------------------------------------------------------------
-8 | 2 | POLYGON((-130 34.64,-125 25.98,-115 25.98,-110 34.64,-115 43.3,-125 43.3,-130 34.64))
-7 | 1 | POLYGON((-115 25.98,-110 17.32,-100 17.32,-95 25.98,-100 34.64,-110 34.64,-115 25.98))
-7 | 2 | POLYGON((-115 43.3,-110 34.64,-100 34.64,-95 43.3,-100 51.96,-110 51.96,-115 43.3))
-6 | 2 | POLYGON((-100 34.64,-95 25.98,-85 25.98,-80 34.64,-85 43.3,-95 43.3,-100 34.64))
进一步阅读:How to divide world into cells (grid)
我有这个问题
WITH buffered AS (
SELECT
ST_Buffer(geom , 10, 'endcap=round join=round') AS geom,
id
FROM line),
hexagons AS (
SELECT
ST_HexagonGrid(10, buffered.geom) AS hex,
buffered.id
FROM buffered
) SELECT * FROM hexagons;
这会在 hex
列中给出 datatype
record
。这是出乎意料的。我预计 geometry
为 datatype
。这是为什么?
根据documentation
,函数ST_HexagonGrid
returns一个setof record
。然而,这些记录包含一个名为 geom
的 geometry
属性,因此为了访问此 record
的 geometry
,您必须用括号 ()
和用点 .
调用属性,例如
SELECT (hex).geom FROM hexagons;
或使用 *
访问获取所有属性(在本例中,i
、j
和 geom
):
SELECT (hex).* FROM hexagons;
演示(PostGIS 3.1):
WITH j (hex) AS (
SELECT
ST_HexagonGrid(
10,ST_Buffer('LINESTRING(-105.55 41.11,-115.48 37.16,-109.29 29.38,-98.34 27.13)',1))
)
SELECT ST_AsText((hex).geom,2) FROM j;
st_astext
----------------------------------------------------------------------------------------
POLYGON((-130 34.64,-125 25.98,-115 25.98,-110 34.64,-115 43.3,-125 43.3,-130 34.64))
POLYGON((-115 25.98,-110 17.32,-100 17.32,-95 25.98,-100 34.64,-110 34.64,-115 25.98))
POLYGON((-115 43.3,-110 34.64,-100 34.64,-95 43.3,-100 51.96,-110 51.96,-115 43.3))
POLYGON((-100 34.64,-95 25.98,-85 25.98,-80 34.64,-85 43.3,-95 43.3,-100 34.64))
作为 ST_HexagonGrid
returns a setof record
,您可以使用 LATERAL
访问记录属性,如 here
所述,或者只调用函数FROM
子句:
SELECT i,j,ST_AsText(geom,2) FROM
ST_HexagonGrid(
10,ST_Buffer('LINESTRING(-105.55 41.11,-115.48 37.16,-109.29 29.38,-98.34 27.13)',1));
i | j | st_astext
----+---+----------------------------------------------------------------------------------------
-8 | 2 | POLYGON((-130 34.64,-125 25.98,-115 25.98,-110 34.64,-115 43.3,-125 43.3,-130 34.64))
-7 | 1 | POLYGON((-115 25.98,-110 17.32,-100 17.32,-95 25.98,-100 34.64,-110 34.64,-115 25.98))
-7 | 2 | POLYGON((-115 43.3,-110 34.64,-100 34.64,-95 43.3,-100 51.96,-110 51.96,-115 43.3))
-6 | 2 | POLYGON((-100 34.64,-95 25.98,-85 25.98,-80 34.64,-85 43.3,-95 43.3,-100 34.64))
进一步阅读:How to divide world into cells (grid)