Class SpatialDWithin

Namespace: YndigoBlue.Velocity.Functions

Assembly: YndigoBlue.Velocity.dll

Represents the ST_DWITHIN spatial function that tests whether two geometries are within a given distance of each other, returning a boolean rather than the distance itself.

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

Inheritance: object

Function

SpatialDWithin

Implements: ICheckItem

IDefaultItem

IFilterItem

IElement

Remarks

Warning

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

SpatialDWithin answers "are these two things within X of each other?" as a single boolean predicate — the same question SpatialDistance answers indirectly by computing an exact distance and comparing it yourself (e.g. new Criterion<double>(new Expression(new SpatialDistance(a, b)), ConditionalType.LessThanOrEqualTo, threshold)). Prefer SpatialDWithin whenever the threshold comparison is the point — a spatially-indexed backend can answer it directly (first narrowing candidates by their bounding box, then confirming the exact distance) instead of computing an exact distance for every row before any comparison can happen.

SpatialDWithin diagram showing a 5km distance threshold around a reference location, with locations inside it evaluating true and one beyond it evaluating false

PostgreSQL only. Unlike every other function in this namespace, ST_DWITHIN (or an equivalent that preserves its indexed-lookup behavior) has no equivalent on any of Velocity's other supported databases today. Calling this function against a non-PostgreSQL connection throws NotSupportedException at query-build time — deliberately, rather than emitting SQL that would fail unpredictably at the database. If your data layer must stay portable across datasources, use SpatialDistance with an explicit threshold comparison instead; it's slower on PostgreSQL (no index pushdown) but works identically everywhere Velocity runs.

Units of Measure. As with SpatialDistance, the distance (or distanceExpression) argument is interpreted against a planar NetTopologySuite.Geometries.Geometry pair in that geometry's own coordinate units (degrees, for the common WGS84 case), and against a Geography pair in meters unless a UnitOfMeasure overload is used, in which case the distance is converted to meters before being evaluated. See UnitOfMeasure.

Examples

var schema = manager.LoadSchema("logistics");
var stores = schema["stores"];
var centers = schema["distribution_centers"];

// Stores within 5 kilometers of any distribution center
var query = new Query()
    .Select(stores["name"])
    .From(stores)
    .Where(new Criterion<bool>(
        new Expression(new SpatialDWithin(stores["location"], centers["location"], 5.0F, UnitOfMeasure.Kilometer)),
        true));

var results = manager.Retrieve(query);

Constructors

SpatialDWithin(Geometry, Column, float): Tests whether a literal geometry is within distance of a geometry column.

SpatialDWithin(Geometry, Function, float): Tests whether a literal geometry is within distance of the result of a spatial function.

SpatialDWithin(Column, Geometry, float): Tests whether a geometry column is within distance of a literal geometry.

SpatialDWithin(Column, Column, float): Tests whether two columns (a spatial join predicate) are within distance of each other.

SpatialDWithin(Column, Column, float, UnitOfMeasure): Tests whether two geography columns (a spatial join predicate) are within distance (expressed in unitOfMeasure) of each other.

SpatialDWithin(Column, Function, float): Tests whether a geometry column is within distance of the result of a spatial function.

SpatialDWithin(Column, Function, float, UnitOfMeasure): Tests whether a geography column is within distance (expressed in unitOfMeasure) of the result of a spatial function.

SpatialDWithin(Column, Geography, float): Tests whether a geography column is within distance meters of a literal geography.

SpatialDWithin(Column, Geography, float, UnitOfMeasure): Tests whether a geography column is within distance (expressed in unitOfMeasure) of a literal geography.

SpatialDWithin(Function, Geometry, float): Tests whether the result of a spatial function is within distance of a literal geometry.

SpatialDWithin(Function, Column, float): Tests whether the result of a spatial function is within distance of a geometry column.

SpatialDWithin(Function, Column, float, UnitOfMeasure): Tests whether the result of a spatial function is within distance (expressed in unitOfMeasure) of a geography column.

SpatialDWithin(Function, Function, float): Tests whether the results of two spatial functions are within distance of each other.

SpatialDWithin(Function, Function, float, UnitOfMeasure): Tests whether the results of two spatial functions are within distance (expressed in unitOfMeasure) of each other.

SpatialDWithin(Function, Geography, float): Tests whether the result of a spatial function is within distance meters of a literal geography.

SpatialDWithin(Function, Geography, float, UnitOfMeasure): Tests whether the result of a spatial function is within distance (expressed in unitOfMeasure) of a literal geography.

SpatialDWithin(Geography, Column, float): Tests whether a literal geography is within distance meters of a geography column.

SpatialDWithin(Geography, Column, float, UnitOfMeasure): Tests whether a literal geography is within distance (expressed in unitOfMeasure) of a geography column.

SpatialDWithin(Geography, Function, float): Tests whether a literal geography is within distance meters of the result of a spatial function.

SpatialDWithin(Geography, Function, float, UnitOfMeasure): Tests whether a literal geography is within distance (expressed in unitOfMeasure) of the result of a spatial function.

Table of Contents

Class SpatialDWithin

Remarks

Warning

Examples

Constructors