Access functions in Lindorm spatiotemporal functions - Lindorm

The access functions of the Lindorm GanosBase spatiotemporal service allow you to quickly retrieve geometric properties, such as points and coordinate values. These functions simplify the spatial data processing flow and improve the ease and accuracy of data analytics. This topic describes the access functions that Lindorm supports.

Engine and version

Access functions apply only to LindormTable. There are no version requirements.

Function list

The following table lists the access functions that Lindorm GanosBase supports.

Function	Description
ST_Centroid	Returns the centroid of a specified Geometry object.
ST_EndPoint	Returns the last point of a specified LineString object.
ST_NPoints	Returns the number of vertices in a specified Geometry object.
ST_StartPoint	Returns the start point of a specified LineString object.
ST_X	Returns the X-coordinate value of a specified Point object.
ST_XMax	Returns the maximum X-coordinate of the bounding box of a specified Geometry object.
ST_XMin	Returns the minimum X-coordinate of the bounding box of a specified Geometry object.
ST_Y	Returns the Y-coordinate value of a specified Point object.
ST_YMax	Returns the maximum Y-coordinate of the bounding box of a specified Geometry object.
ST_YMin	Returns the minimum Y-coordinate of the bounding box of a specified Geometry object.

ST_Centroid

Returns the centroid of a specified Geometry object.

Syntax

geometry ST_Centroid(geometry g)

Parameter description

Parameter	Description
g	The specified Geometry object.

Note

If the Geometry object is empty, this function returns an empty geometry.

Examples

Example 1

SELECT ST_AsText(ST_Centroid(ST_Collect(ST_MakePoint(1,1),ST_MakePoint(-1,-1)))) AS astext;

The following result is returned:

+-------------+
|   astext    |
+-------------+
| POINT (0 0) |
+-------------+

Example 2

SELECT ST_AsText(ST_Centroid(ST_GeomFromText('LINESTRING(0 0,0 1,1 2)'))) AS astext;

The following result is returned:

+--------------------------------+
|             astext             |
+--------------------------------+
| POINT (0.2928932188134525      |
| 1.085786437626905)             |
+--------------------------------+

ST_EndPoint

Returns the last point of a specified LineString object.

Syntax

geometry ST_EndPoint(geometry g)

Parameter description

Parameter	Description
g	The specified Geometry object.

Note

If the Geometry object is not of the LineString type, this function returns NULL.

Example

SELECT ST_AsText(ST_EndPoint(ST_GEOMFROMTEXT('LINESTRING(1 1, 2 2, 3 3)'))) AS endpoint;

The following result is returned:

+-------------+
|  endpoint   |
+-------------+
| POINT (3 3) |
+-------------+

ST_NPoints

Returns the number of vertices in a specified Geometry object. This function applies to any Geometry object.

Syntax

int ST_NPoints(geometry g)

Parameter description

Parameter	Description
g	The specified Geometry object.

Example

SELECT ST_NPoints(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)')) AS npoints;

The following result is returned:

+---------+
| npoints |
+---------+
| 4       |
+---------+

ST_StartPoint

Returns the start point of a specified LineString object.

Syntax

geometry ST_StartPoint(geometry g)

Parameter description

Parameter	Description
g	The specified Geometry object.

Note

If the Geometry object is not of the LineString type, this function returns NULL.

Example

SELECT ST_AsText(ST_StartPoint(ST_GEOMFROMTEXT('LINESTRING(0 1, 0 2)'))) AS startpoint;

The following result is returned:

+-------------+
| startpoint  |
+-------------+
| POINT (0 1) |
+-------------+

ST_X

Returns the X-coordinate value of a specified Point object.

Syntax

BigDecimal ST_X(geometry a_point)

Parameter description

Parameter	Description
a_point	The specified Point object.

Note

The input Geometry object must be of the Point type. If the input Geometry object is EMPTY or the input value is NULL, this function returns NULL.

Example

SELECT ST_X(ST_MakePoint(1.0, 2.0)) AS x;

The following result is returned:

+---+
| x |
+---+
| 1 |
+---+

ST_XMax

Returns the maximum X-coordinate of the bounding box of a specified Geometry object.

Syntax

BigDecimal ST_XMax(geometry g)

Parameter description

Parameter	Description
g	The specified Geometry object.

Note

The Geometry object can be a Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon, or GeometryCollection object.
If the Geometry object is EMPTY, this function returns -1.

Example

SELECT ST_XMax(ST_GeomFromText('LINESTRING(1 3,5 6)')) AS xmax;

The following result is returned:

+------+
| xmax |
+------+
| 5    |
+------+

ST_XMin

Returns the minimum X-coordinate of the bounding box of a specified Geometry object.

Syntax

BigDecimal ST_XMin(geometry g)

Parameter description

Parameter	Description
g	The specified Geometry object.

Note

The Geometry object can be a Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon, or GeometryCollection object.
If the Geometry object is EMPTY, this function returns 0.

Example

SELECT ST_XMin(ST_GeomFromText('LINESTRING(1 3,5 6)')) AS xmin;

The following result is returned:

+------+
| xmin |
+------+
| 1    |
+------+

ST_Y

Returns the Y-coordinate value of a specified Point object.

Syntax

BigDecimal ST_Y(geometry a_point)

Parameter description

Parameter	Description
a_point	The specified Point object.

Note

The Geometry object must be of the Point type. If the input Geometry object is EMPTY or the input value is NULL, this function returns NULL.

Example

SELECT ST_Y(ST_MakePoint(1.0, 2.0)) AS y;

The following result is returned:

+---+
| y |
+---+
| 2 |
+---+

ST_YMax

Returns the maximum Y-coordinate of the bounding box of a specified Geometry object.

Syntax

BigDecimal ST_YMax(geometry g)

Parameter description

Parameter	Description
g	The specified Geometry object.

Note

The Geometry object can be a Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon, or GeometryCollection object.
If the Geometry object is EMPTY, this function returns -1.

Example

SELECT ST_YMax(ST_GeomFromText('LINESTRING(1 3,5 6)')) AS ymax;

The following result is returned:

+------+
| ymax |
+------+
| 6    |
+------+

ST_YMin

Returns the minimum Y-coordinate of the bounding box of a specified Geometry object.

Syntax

BigDecimal ST_YMin(geometry g)

Parameter description

Parameter	Description
g	The specified Geometry object.

Note

The Geometry object can be a Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon, or GeometryCollection object.
If the Geometry object is EMPTY, this function returns 0.

Example

SELECT ST_YMin(ST_GeomFromText('LINESTRING(1 3,5 6)')) AS ymin;

The following result is returned:

+------+
| ymin |
+------+
| 3    |
+------+