Spatial Functions

Beacon holds 123 spatial functions with PostGIS names: 118 scalar functions, 3 aggregate functions and 2 window functions. This page lists every one of them.

A name is case insensitive. ST_Distance and st_distance are the same function.

Beacon adds two spatial functions of its own. Those sit in the function reference.

Types in the tables below

Type	Meaning
GEOMETRY	A geometry value. A GeoParquet column holds one. ST_Point builds one.
BOX	A bounding box. It holds four DOUBLE values. ST_Envelope and ST_Extent return one.
DOUBLE	A 64 bit float.
INTEGER	A 32 bit integer.
BOOLEAN	True or false.
VARCHAR	Text.
VARBINARY	Bytes.
LIST	A list of VARBINARY. ST_Dump returns one.

constant after an argument type means the argument must be a literal. A column in that position gives an error at plan time. Such an argument drives a setup step per batch, so the function cannot rebuild it per row.

Build a geometry

A netCDF, Zarr, CSV or Parquet table holds coordinate columns, not geometry. ST_Point builds a geometry from two columns:

SELECT ST_AsText(ST_Point(longitude, latitude)) AS point
FROM read_parquet(['obs/*.parquet'])

A column without geometry metadata also reads as a geometry. A VARCHAR column reads as WKT. A VARBINARY column reads as WKB. So a raw CSV column needs no cast.

A GeoParquet file holds a geometry column, and Beacon decodes it to native GeoArrow on read. Every function here reads such a column directly:

SELECT ST_AsText(ST_Extent(geometry)) AS extent
FROM read_geoparquet(['spatial/stations/*.geoparquet'])

TIP

A filter over a GeoParquet geometry column also skips row groups. See what the scan skips.

Accessors

An accessor reads one property of a geometry.

Function	Arguments	Returns	Description
ST_X(geom)	geom GEOMETRY	DOUBLE	X ordinate of a point. It copies no data on a point column with separate coordinates.
ST_Y(geom)	geom GEOMETRY	DOUBLE	Y ordinate of a point.
ST_Z(geom)	geom GEOMETRY	DOUBLE	Z ordinate. A 2D geometry returns NULL.
ST_M(geom)	geom GEOMETRY	DOUBLE	Measure value. A geometry without a measure returns NULL.
ST_SRID(geom)	geom GEOMETRY	INTEGER	Coordinate reference system of the column. Every row returns the same value.
ST_GeometryType(geom)	geom GEOMETRY	VARCHAR	Type name, such as ST_Point.
ST_Dimension(geom)	geom GEOMETRY	INTEGER	Topological dimension: 0, 1 or 2.
ST_CoordDim(geom)	geom GEOMETRY	INTEGER	Number of ordinates per coordinate: 2, 3 or 4.
ST_NPoints(geom)	geom GEOMETRY	INTEGER	Number of coordinates, at any depth.
ST_NumPoints(geom)	geom GEOMETRY	INTEGER	Number of points of a line string. Another type returns NULL.
ST_NumGeometries(geom)	geom GEOMETRY	INTEGER	Number of parts of a collection.
ST_NumInteriorRings(geom)	geom GEOMETRY	INTEGER	Number of holes of a polygon.
ST_IsEmpty(geom)	geom GEOMETRY	BOOLEAN	True for an empty geometry.
ST_IsClosed(geom)	geom GEOMETRY	BOOLEAN	True when the start point equals the end point.
ST_IsRing(geom)	geom GEOMETRY	BOOLEAN	True for a line string that is closed and simple.
ST_IsSimple(geom)	geom GEOMETRY	BOOLEAN	True when a geometry crosses itself nowhere. An areal geometry is always simple.

Components

A component function returns one part of a geometry.

Function	Arguments	Returns	Description
ST_StartPoint(geom)	geom GEOMETRY	GEOMETRY	First point of a line string.
ST_EndPoint(geom)	geom GEOMETRY	GEOMETRY	Last point of a line string.
ST_PointN(geom, n)	geom GEOMETRY, n INTEGER	GEOMETRY	Point n of a line string. The index starts at 1. An index outside the line returns NULL.
ST_ExteriorRing(geom)	geom GEOMETRY	GEOMETRY	Shell of a polygon, as a line string.
ST_InteriorRingN(geom, n)	geom GEOMETRY, n INTEGER	GEOMETRY	Hole n of a polygon. The index starts at 1.
ST_GeometryN(geom, n)	geom GEOMETRY, n INTEGER	GEOMETRY	Part n of a collection. Index 1 returns the input when the input is no collection.

Constructors

A constructor builds a geometry from plain columns.

Function	Arguments	Returns	Description
ST_Point(x, y[, z])	x DOUBLE, y DOUBLE, z DOUBLE	GEOMETRY	Point from two or three ordinate columns. It adopts the input buffers and copies nothing. A third argument sets z, not the SRID.
ST_MakePoint(x, y[, z])	x DOUBLE, y DOUBLE, z DOUBLE	GEOMETRY	The same function, under the PostGIS alias.
ST_PointZ(x, y[, z])	x DOUBLE, y DOUBLE, z DOUBLE	GEOMETRY	The same function. Two arguments return a 2D point. PostGIS needs three.
ST_MakeLine(a, b)	a GEOMETRY, b GEOMETRY	GEOMETRY	Two-point line from two point columns. There is no aggregate form.
ST_MakePolygon(ring)	ring GEOMETRY	GEOMETRY	Polygon from a closed line string. It builds the shell only, with no holes.
ST_MakeEnvelope(x1, y1, x2, y2)	four DOUBLE	GEOMETRY	Rectangle from four ordinates. It adopts all four input buffers. There is no fifth srid argument.
ST_MakeBox2D(x1, y1, x2, y2)	four DOUBLE	BOX	Box from four ordinates. PostGIS takes two points here.

Input and output

Function	Arguments	Returns	Description
ST_AsText(geom)	geom GEOMETRY	VARCHAR	WKT text. There is no maxdecimaldigits argument.
ST_AsBinary(geom)	geom GEOMETRY	VARBINARY	WKB bytes.
ST_AsEWKB(geom)	geom GEOMETRY	VARBINARY	Extended WKB bytes. The SRID comes from the column metadata.
ST_AsGeoJSON(geom)	geom GEOMETRY	VARCHAR	GeoJSON text. It accepts a geometry only, not a row.
ST_GeomFromText(wkt)	wkt VARCHAR	GEOMETRY	Geometry from WKT. There is no srid argument. Call ST_SetSRID after it.
ST_GeomFromWKB(bytes)	bytes VARBINARY	GEOMETRY	Geometry from WKB.
ST_GeomFromEWKB(bytes)	bytes VARBINARY	GEOMETRY	Geometry from extended WKB. The SRID inside the value is lost. Call ST_SetSRID after it.
ST_GeomFromGeoJSON(json)	json VARCHAR	GEOMETRY	Geometry from GeoJSON.
ST_GeoHash(geom[, prec])	geom GEOMETRY, prec INTEGER	VARCHAR	Geohash of a point. Another type returns NULL. The default precision is 20.
ST_PointFromGeoHash(hash)	hash VARCHAR	GEOMETRY	Centre point of a geohash cell. There is no precision argument.

Predicates

A predicate compares two geometries and returns true or false. Each one runs a bounding box test first. The exact test then runs on the rows that pass.

Function	Arguments	Returns	Description
ST_Intersects(a, b)	a GEOMETRY, b GEOMETRY	BOOLEAN	True when the two share a point.
ST_Disjoint(a, b)	a GEOMETRY, b GEOMETRY	BOOLEAN	True when the two share no point.
ST_Contains(a, b)	a GEOMETRY, b GEOMETRY	BOOLEAN	True when a holds b.
ST_ContainsProperly(a, b)	a GEOMETRY, b GEOMETRY	BOOLEAN	True when a holds b and the boundaries meet nowhere.
ST_Within(a, b)	a GEOMETRY, b GEOMETRY	BOOLEAN	True when b holds a.
ST_Covers(a, b)	a GEOMETRY, b GEOMETRY	BOOLEAN	True when every point of b lies in a.
ST_CoveredBy(a, b)	a GEOMETRY, b GEOMETRY	BOOLEAN	The reverse of ST_Covers.
ST_Touches(a, b)	a GEOMETRY, b GEOMETRY	BOOLEAN	True when only the boundaries meet.
ST_Crosses(a, b)	a GEOMETRY, b GEOMETRY	BOOLEAN	True when the interiors cross.
ST_Overlaps(a, b)	a GEOMETRY, b GEOMETRY	BOOLEAN	True when the two overlap in part.
ST_Equals(a, b)	a GEOMETRY, b GEOMETRY	BOOLEAN	True when the two cover the same points.
ST_Relate(a, b)	a GEOMETRY, b GEOMETRY	VARCHAR	The nine character DE-9IM matrix.
ST_Relate(a, b, pattern)	a GEOMETRY, b GEOMETRY, pattern VARCHAR constant	BOOLEAN	True when the matrix matches the pattern.
ST_DWithin(a, b, d)	a GEOMETRY, b GEOMETRY, d DOUBLE constant	BOOLEAN	True when the distance is d or less.
ST_DFullyWithin(a, b, d)	a GEOMETRY, b GEOMETRY, d DOUBLE constant	BOOLEAN	True when every point pair lies within d.
ST_BBoxIntersects(a, b)	a GEOMETRY, b GEOMETRY	BOOLEAN	True when the two bounding boxes overlap. PostGIS writes this as the && operator.

Measurement

Every measurement is planar. Longitude and latitude data therefore returns degrees, not metres. ST_DistanceSphere and ST_DistanceSpheroid are the two exceptions. Both return metres.

Function	Arguments	Returns	Description
ST_Area(geom)	geom GEOMETRY	DOUBLE	Area.
ST_Length(geom)	geom GEOMETRY	DOUBLE	Length of the lineal parts. A polygon returns zero.
ST_Perimeter(geom)	geom GEOMETRY	DOUBLE	Perimeter of the areal parts.
ST_Distance(a, b)	a GEOMETRY, b GEOMETRY	DOUBLE	Shortest distance.
ST_MaxDistance(a, b)	a GEOMETRY, b GEOMETRY	DOUBLE	Largest distance between two vertices. The cost is the product of the two vertex counts.
ST_HausdorffDistance(a, b)	a GEOMETRY, b GEOMETRY	DOUBLE	Hausdorff distance. There is no densifyFrac argument.
ST_FrechetDistance(a, b)	a GEOMETRY, b GEOMETRY	DOUBLE	Fréchet distance of two line strings. Another type returns NULL.
ST_DistanceSphere(a, b)	a GEOMETRY, b GEOMETRY	DOUBLE	Distance of two points on a sphere, in metres. It takes two points only.
ST_DistanceSpheroid(a, b)	a GEOMETRY, b GEOMETRY	DOUBLE	Distance of two points on WGS 84, in metres. There is no spheroid argument.

Linear reference

Function	Arguments	Returns	Description
ST_ClosestPoint(a, b)	a GEOMETRY, b GEOMETRY	GEOMETRY	Point of a nearest to b.
ST_ShortestLine(a, b)	a GEOMETRY, b GEOMETRY	GEOMETRY	Line between the two nearest points.
ST_LineLocatePoint(line, pt)	line GEOMETRY, pt GEOMETRY	DOUBLE	Position of a point on a line, from 0 to 1.
ST_LineInterpolatePoint(line, f)	line GEOMETRY, f DOUBLE	GEOMETRY	Point at fraction f of a line. A fraction outside 0 to 1 returns NULL.

Overlay

Each overlay function takes areal arguments only. Another type returns NULL.

Function	Arguments	Returns	Description
ST_Union(a, b)	a GEOMETRY, b GEOMETRY	GEOMETRY	Union of two areal geometries.
ST_Intersection(a, b)	a GEOMETRY, b GEOMETRY	GEOMETRY	Common part of two areal geometries.
ST_Difference(a, b)	a GEOMETRY, b GEOMETRY	GEOMETRY	Part of a outside b.
ST_SymDifference(a, b)	a GEOMETRY, b GEOMETRY	GEOMETRY	Part of either one, but not of both.

ST_Union with one argument is an error. PostGIS gives that name to an aggregate, and one name cannot serve both registries here. The aggregate is ST_MemUnion.

Processing

Function	Arguments	Returns	Description
ST_Buffer(geom, d)	geom GEOMETRY, d DOUBLE	GEOMETRY	Area within distance d. It uses round joins and round caps. There is no style argument.
ST_ConvexHull(geom)	geom GEOMETRY	GEOMETRY	Smallest convex polygon around a geometry.
ST_ConcaveHull(geom, pct)	geom GEOMETRY, pct DOUBLE	GEOMETRY	Concave hull. It supports no holes.
ST_OrientedEnvelope(geom)	geom GEOMETRY	GEOMETRY	Smallest rectangle of any angle.
ST_Boundary(geom)	geom GEOMETRY	GEOMETRY	Boundary of a geometry. A collection returns an empty boundary.
ST_Centroid(geom)	geom GEOMETRY	GEOMETRY	Centre of mass.
ST_PointOnSurface(geom)	geom GEOMETRY	GEOMETRY	A point that lies on the geometry.
ST_Simplify(geom, tol)	geom GEOMETRY, tol DOUBLE	GEOMETRY	Ramer-Douglas-Peucker simplification. There is no preserveCollapsed flag.
ST_SimplifyVW(geom, tol)	geom GEOMETRY, tol DOUBLE	GEOMETRY	Visvalingam-Whyatt simplification.
ST_Segmentize(geom, max)	geom GEOMETRY, max DOUBLE	GEOMETRY	Split every segment longer than max. A length of zero or less returns NULL.
ST_RemoveRepeatedPoints(geom)	geom GEOMETRY	GEOMETRY	Drop repeated coordinates. There is no tolerance argument.
ST_Reverse(geom)	geom GEOMETRY	GEOMETRY	Reverse the coordinate order.
ST_ForcePolygonCCW(geom)	geom GEOMETRY	GEOMETRY	Counter-clockwise shell.
ST_ForcePolygonCW(geom)	geom GEOMETRY	GEOMETRY	Clockwise shell.
ST_Force2D(geom)	geom GEOMETRY	GEOMETRY	Drop the Z ordinate. It drops one buffer handle and copies nothing.
ST_Force3D(geom)	geom GEOMETRY	GEOMETRY	Add a Z ordinate of zero.
ST_FlipCoordinates(geom)	geom GEOMETRY	GEOMETRY	Swap X and Y. It swaps two buffer handles and copies nothing.
ST_SetSRID(geom, srid)	geom GEOMETRY, srid INTEGER constant	GEOMETRY	Set the coordinate reference system. It reads no row, because it changes the column type.

ST_SimplifyPreserveTopology is absent. The library behind these functions has no topology-safe simplification. ST_SimplifyVW is close, but it gives no guarantee.

Validity

Function	Arguments	Returns	Description
ST_IsValid(geom)	geom GEOMETRY	BOOLEAN	True for a valid geometry.
ST_IsValidReason(geom)	geom GEOMETRY	VARCHAR	Text that names the fault. A valid geometry returns Valid Geometry.
ST_MakeValid(geom)	geom GEOMETRY	GEOMETRY	Repair an areal geometry. Another type passes through.

Affine

Every argument after the geometry must be a constant.

Function	Arguments	Returns	Description
ST_Translate(geom, dx, dy)	geom GEOMETRY, dx DOUBLE constant, dy DOUBLE constant	GEOMETRY	Move a geometry. There is no 3D form.
ST_Scale(geom, xf, yf)	geom GEOMETRY, xf DOUBLE constant, yf DOUBLE constant	GEOMETRY	Scale about the origin.
ST_Rotate(geom, rad)	geom GEOMETRY, rad DOUBLE constant	GEOMETRY	Rotate about the origin. The angle is in radians.
ST_Affine(geom, a, b, d, e, xoff, yoff)	geom GEOMETRY, six DOUBLE constant	GEOMETRY	2D affine transform. There is no twelve argument 3D form.

Bounding box

A box column holds four DOUBLE buffers. An ordinate accessor therefore hands back one buffer and allocates nothing.

Function	Arguments	Returns	Description
ST_Envelope(geom)	geom GEOMETRY	BOX	Bounding box of a geometry. It reads as ST_Polygon.
ST_Expand(geom, d)	geom GEOMETRY, d DOUBLE	BOX	Bounding box grown by d. There is no per-axis form.
ST_XMin(geom)	geom GEOMETRY or BOX	DOUBLE	Smallest X.
ST_YMin(geom)	geom GEOMETRY or BOX	DOUBLE	Smallest Y.
ST_XMax(geom)	geom GEOMETRY or BOX	DOUBLE	Largest X.
ST_YMax(geom)	geom GEOMETRY or BOX	DOUBLE	Largest Y.
ST_ZMin(geom)	geom GEOMETRY or BOX	DOUBLE	Always NULL. The box pass is two-dimensional.
ST_ZMax(geom)	geom GEOMETRY or BOX	DOUBLE	Always NULL.

Tessellation

Function	Arguments	Returns	Description
ST_DelaunayTriangles(geom)	geom GEOMETRY	GEOMETRY	Delaunay triangulation. It always returns a collection.
ST_VoronoiPolygons(geom)	geom GEOMETRY	GEOMETRY	Voronoi cells as polygons. It clips each cell to the input extent plus 50 percent.
ST_VoronoiLines(geom)	geom GEOMETRY	GEOMETRY	Voronoi cell edges as lines.
ST_ChaikinSmoothing(geom, n)	geom GEOMETRY, n INTEGER	GEOMETRY	Chaikin smoothing. The limit is 8 rounds, because each round doubles the vertex count.

Bearings

Function	Arguments	Returns	Description
ST_Azimuth(a, b)	a GEOMETRY, b GEOMETRY	DOUBLE	Bearing of two points, in radians clockwise from north, on WGS 84. Two equal points return NULL.
ST_Project(pt, dist, azim)	pt GEOMETRY, dist DOUBLE, azim DOUBLE	GEOMETRY	Point at a distance in metres and a bearing in radians, on WGS 84.

Edits

Function	Arguments	Returns	Description
ST_Multi(geom)	geom GEOMETRY	GEOMETRY	Wrap a geometry in its multi form.
ST_Points(geom)	geom GEOMETRY	GEOMETRY	Every coordinate as one multi point.
ST_SnapToGrid(geom, size)	geom GEOMETRY, size DOUBLE	GEOMETRY	Round every coordinate onto a grid. One size serves both axes. A size of zero or less returns NULL.
ST_AddPoint(line, pt[, pos])	line GEOMETRY, pt GEOMETRY, pos INTEGER	GEOMETRY	Add a point to a line string. The index starts at 0. It appends when you omit the position.
ST_RemovePoint(line, pos)	line GEOMETRY, pos INTEGER	GEOMETRY	Remove a point from a line string. It returns NULL when fewer than two vertices remain.
ST_SetPoint(line, pos, pt)	line GEOMETRY, pos INTEGER, pt GEOMETRY	GEOMETRY	Replace a point of a line string. Note the order: the position comes first.
ST_Dump(geom)	geom GEOMETRY	LIST	Parts of a collection, as a list of WKB.

ST_Dump returns a list, because a scalar function returns one value per row. Expand it with unnest:

SELECT ST_AsText(unnest(ST_Dump(geometry))) AS part
FROM read_geoparquet(['shapes/*.geoparquet'])

The parts are WKB, not geometry. unnest drops the metadata of the child field, so a list of geometry arrives as a plain struct. A VARBINARY column always reads as WKB, so the parts stay usable with no cast.

Aggregate functions

An aggregate function reads every row of a group and returns one value.

Function	Arguments	Returns	Description
ST_Extent(geom)	geom GEOMETRY	BOX	Bounding box of every row. The state is four DOUBLE values, so it builds no geometry.
ST_Collect(geom)	geom GEOMETRY	GEOMETRY	Every row as one geometry collection. PostGIS returns a multi type for one input type.
ST_MemUnion(geom)	geom GEOMETRY	GEOMETRY	Union of every row. PostGIS also calls this ST_Union.

Read the box of ST_Extent with the four ordinate accessors:

SELECT ST_XMin(ST_Extent(ST_Point(longitude, latitude))) AS west,
       ST_XMax(ST_Extent(ST_Point(longitude, latitude))) AS east,
       ST_YMin(ST_Extent(ST_Point(longitude, latitude))) AS south,
       ST_YMax(ST_Extent(ST_Point(longitude, latitude))) AS north
FROM read_parquet(['obs/*.parquet'])

Window functions

Both cluster functions read every row of a partition at once. PostGIS defines them as window functions, and so does Beacon. Each one needs OVER ().

Function	Arguments	Returns	Description
ST_ClusterKMeans(geom, k)	geom GEOMETRY, k INTEGER	INTEGER	Group the rows into k clusters. A fixed seed makes the query repeatable. There is no max_radius argument.
ST_ClusterDBSCAN(geom, eps, min)	geom GEOMETRY, eps DOUBLE, min INTEGER	INTEGER	Group the rows by density. Noise returns NULL.

Both functions cluster the centroids. PostGIS uses the whole geometry, so a large geometry can give another answer.

SELECT platform,
       ST_ClusterKMeans(ST_Point(longitude, latitude), 5) OVER () AS cluster
FROM read_parquet(['obs/*.parquet'])

Reprojection

Function	Arguments	Returns	Description
ST_Transform(geom, srid)	geom GEOMETRY, srid INTEGER constant	GEOMETRY	Reproject a geometry to the target srid.

The source system comes from the column metadata. Set it first when the file states none:

SELECT ST_AsText(ST_Transform(ST_SetSRID(ST_Point(longitude, latitude), 4326), 3035)) AS point
FROM read_parquet(['obs/*.parquet'])

The function takes an EPSG code, not a PROJ string.

ST_Transform links PROJ, a C++ library, and a standard Beacon build ships it. A build from source therefore needs PROJ 9.6.2 or later, beside the netCDF and HDF5 it already needs:

sudo apt-get install -y libproj-dev pkg-config   # Debian and Ubuntu
brew install proj pkg-config                     # macOS

Two build options cover a machine without PROJ. --features spatial-proj-bundled builds PROJ from source. --no-default-features drops ST_Transform, and the other 122 functions stay.

Differences from PostGIS

Four rules explain most of the differences. Each table above marks the rest per function.

• The coordinate reference system belongs to the column. GeoArrow holds it once, in the column metadata. ST_SRID therefore returns one value for every row, and ST_SetSRID needs a constant. One PostGIS column can hold rows in different systems. A Beacon column cannot.
• A constant argument stays constant. A radius, a pattern, an SRID or a matrix drives a setup step per batch. A column in that position gives an error at plan time.
• A row that does not fit returns NULL. PostGIS raises an error for a wrong geometry type. One bad row does not stop a query here. A wrong static type is still an error at plan time.
• A plain column reads by its type. A VARCHAR column reads as WKT. A VARBINARY column reads as WKB. One surprise follows: ST_AsText on any text column returns that text. Pass such a column through ST_GeomFromText to check the parse step.

Functions that are absent

Area	PostGIS functions	Reason
Geography type	every geography overload	It needs a second type and a spherical algorithm set.
Edits	ST_Snap, ST_Node, ST_Split, ST_LineMerge, ST_LineSubstring, ST_Subdivide	The library behind these functions has no equivalent.
3D	ST_3DDistance, ST_3DIntersects, ST_3DLength and the rest	That library is two-dimensional.
Other output	ST_AsGML, ST_AsKML, ST_AsSVG, ST_AsMVT	Beacon needs a writer per format.
Simplification	ST_SimplifyPreserveTopology	No topology-safe simplification exists there.
Set output	ST_DumpPoints, ST_DumpRings	These have the shape of ST_Dump. ST_Points covers the common use.

:::note SHOW FUNCTIONS lists 10 of these functions. It reads information_schema.parameters, and a function that accepts any argument type states no argument types. Such a function gets no row there. Every function on this page runs, listed or not. Use this page as the reference. See datafusion-spatial#1. :::