Name
ST_Expand — 入力ジオメトリのバウンディングボックスから全ての方向に拡張されたバウンディングボックスを返します。倍精度浮動小数点数を使います。
Synopsis
geometry ST_Expand(geometry geom, float units_to_expand);
geometry ST_Expand(geometry geom, float dx, float dy, float dz=0, float dm=0);
box2d ST_Expand(box2d box, float units_to_expand);
box2d ST_Expand(box2d box, float dx, float dy);
box3d ST_Expand(box3d box, float units_to_expand);
box3d ST_Expand(box3d box, float dx, float dy, float dz=0);
説明
This function returns a bounding box expanded from the bounding box of the input, either by specifying a single distance with which the box should be expanded in all directions, or by specifying an expansion distance for each direction. Uses double-precision. Can be very useful for distance queries, or to add a bounding box filter to a query to take advantage of a spatial index.
In addition to the geometry version of ST_Expand, which is the most commonly used, variants are provided that accept and produce internal BOX2D and BOX3D data types.
ST_Expand is similar in concept to ST_Buffer, except while buffer expands the geometry in all directions, ST_Expand expands the bounding box an x,y,z unit amount.
Units are in the units of the spatial reference system in use denoted by the SRID.
![[Note]](images/note.png) | |
1.3より前は、ST_Expandは、インデクスを利用するクエリを実行するために、distanceと併せて使用されていました。形式は |
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Availability: 1.5.0 出力をfloat4座標値から倍精度に変更しました。 Enhanced: 2.0.0 多面体サーフェス対応、三角対応、TIN対応が導入されました。 Enhanced: 2.3.0 support was added to expand a box by different amounts in different dimensions. |
This function supports Polyhedral surfaces.
This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).
例
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次に示す例では、メートル単位の投影法である米国ナショナルアトラス正積図法 (SRID=2163)を使っています。 |
-- ラインストリングのバウンディングボックスを10メートル拡張
SELECT CAST(ST_Expand(ST_GeomFromText('LINESTRING(2312980 110676,2312923 110701,2312892 110714)', 2163),10) As box2d);
st_expand
------------------------------------
BOX(2312882 110666,2312990 110724)
--10 meter expanded 3d box of a 3d box
SELECT ST_Expand(CAST('BOX3D(778783 2951741 1,794875 2970042.61545891 10)' As box3d),10)
st_expand
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BOX3D(778773 2951731 -9,794885 2970052.61545891 20)
-- 3次元ボックスを10メートル拡張
SELECT ST_AsEWKT(ST_Expand(ST_GeomFromEWKT('SRID=2163;POINT(2312980 110676)'),10));
st_asewkt
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SRID=2163;POLYGON((2312970 110666,2312970 110686,2312990 110686,2312990 110666,2312970 110666))