Class SpatialNumGeometries

Namespace

YndigoBlue.Velocity.Functions

Assembly

YndigoBlue.Velocity.dll

Represents the ST_NumGeometries spatial property function that returns the number of component geometries in a geometry collection.

public class SpatialNumGeometries : Function, ICheckItem, IDefaultItem, IFilterItem, IElement

Inheritance

object

Function

SpatialNumGeometries

Implements

ICheckItem

IDefaultItem

IFilterItem

IElement

Remarks

Warning

Spatial functions are not available in the Community Edition of Velocity. They require the Full Edition.

The ST_NumGeometries function returns the count of geometries within a geometry collection, multi-point, multi-linestring, or multi-polygon. For simple geometries (point, linestring, polygon), returns 1. For empty geometry collections, returns 0. This is useful for analyzing multi-part features, identifying complex geometries, or iterating through geometry collection components. For Geometry types in planar coordinate systems, helpful for understanding feature complexity and structure. OGC-compliant.

Return Type: Integer (count of geometries).

Geometry Type	ST_NumGeometries Result
Point, LineString, Polygon	1
MultiPoint (4 points)	4
MultiLineString (3 lines)	3
MultiPolygon (2 polygons)	2
GeometryCollection	Count of top-level geometries
Empty collection	0

Examples

Count the number of component geometries in each multi-geometry feature:

var schema = manager.LoadSchema("gis");
var features = schema["features"];

var query = new Query()
    .Select([ features["id"], new Expression("part_count", new SpatialNumGeometries(features["shape"])) ])
    .From(features);

var results = manager.Retrieve(query);

Constructors

SpatialNumGeometries(Geometry)

Initializes a new instance of ST_NumGeometries with a geometry literal.

SpatialNumGeometries(Column)

Initializes a new instance of ST_NumGeometries with a geometry column.

SpatialNumGeometries(Function)

Initializes a new instance of ST_NumGeometries for a function result.

SpatialNumGeometries(Geography)

Initializes a new instance of ST_NumGeometries with a geography literal.