Lindorm spatio-temporal functions - - Alibaba Cloud Documentation Center

Spatio-temporal functions analyze and calculate spatio-temporal data in scenarios that require spatio-temporal range query, geofence determination, and spatio-temporal data mining, such as ride-hailing, urban traffic planning, and navigation. This topic describes the spatio-temporal functions supported by the Lindorm streaming engine.

Category	Function	Description
Output functions	ST_AsText	Returns the information about a geometry object in Well-known Text (WKT) format.
Constructor functions	ST_GeomFromText	Constructs a geometry object based on the specified WKT string.
	ST_LineFromMultiPoint	Constructs a LineString object based on the specified MultiPoint object.
	ST_MakePoint	Constructs a point object.
	ST_MakeLine	Constructs a LineString object.
Access functions	ST_Centroid	Returns the centroid of the specified geometry object.
	ST_EndPoint	Returns the last point of the specified LineString object.
	ST_NPoints	Returns the number of vertexes in the specified geometry object.
	ST_StartPoint	Returns the start point of the specified LineString object.
	ST_X	Returns the x coordinate of the specified point object.
	ST_XMax	Returns the maximum x coordinate on the bounding box of the specified geometry object.
	ST_XMin	Returns the minimum x coordinate on the bounding box of the specified geometry object.
	ST_Y	Returns the y coordinate of the specified point object.
	ST_YMax	Returns the maximum y coordinate on the bounding box of the specified geometry object.
	ST_YMin	Returns the minimum y coordinate on the bounding box of the specified geometry object.
Functions for spatial relationships	ST_Contains	Checks whether the first geometry object that you specify contains the second geometry object that you specify. If the first geometry object contains the second geometry object, this function returns true.
	ST_DWithin	Checks whether the 2D distance between two geometry objects is within the specified range. If the 2D distance between the objects is within the specified range, this function returns true.
	ST_DWithinSphere	Checks whether the spherical distance between two geometry objects is within the specified range. If the spherical distance between the objects is within the specified range, this function returns true.
	ST_Intersects	Checks whether two geometry objects intersect. If the two geometry objects have any shared spatial space, this function determines that the two objects intersect and returns true.
	ST_Overlaps	Checks whether two geometry objects spatially overlap but one is not contained in the other. If the two geometry objects spatially overlap but one is not contained in the other, this function returns true.
	ST_Within	Checks whether the second geometry object that you specify is completely within the first geometry object that you specify. If the second geometry object is completely within the first geometry object, this function returns true.
	ST_Equals	Checks whether two geometry objects are spatially equal. If the two geometry objects are spatially equal, this function returns true.
Processing functions	ST_Buffer	Returns a buffer geometry object consisting of all points whose 2D distance to a specified source geometry object is equal to the specified radius.
	ST_BufferSphere	Returns a buffer geometry object consisting of all points whose spherical distance to a specified source geometry object is equal to the specified radius.
	ST_Difference	Returns a geometry object representing the part that the first geometry object that you specify does not intersect with the second geometry object that you specify.
	ST_MinimumBoundingCircle	Returns the smallest circle that can fully contain the specified geometry object.
	ST_MinimumBoundingRadius	Returns the radius of the smallest circle that can fully contain the specified geometry object.
	ST_Intersection	Returns a geometry object representing the part that the first geometry object that you specify intersects with the second geometry object that you specify.
Measurement functions	ST_Area	Calculates the area of the specified polygon object.
	ST_Distance	Calculates the 2D Euclidean distance between two specified geometry objects. The returned distance is measured in degrees.
	ST_DistanceSphere	Calculates the minimum spherical distance between two specified geometry objects. The returned distance is measured in meters. If one of the specified geometry object is a polygon or LineString object, the results may have an error of centimeters.
	ST_Length	Calculates the 2D length of the specified geometry object. The returned length is measured in degrees.
	ST_LengthSphere	Calculates the spherical length of the specified geometry object. The returned length is measured in meters.
Aggregate functions	ST_MakeLine_Agg	Constructs a LineString object based on the specified geometry object. This function does not sort the data.
Aggregate functions	ST_MakeLine_Ts_Agg	Constructs a LineString object based on the specified geometry object and sorts data based on the timestamp column.