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geo/geomfn: implement ST_SymDifference #53636

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Aug 30, 2020
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geo/geomfn: implement ST_SymDifference #53636

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3 changes: 3 additions & 0 deletions docs/generated/sql/functions.md
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Original file line number Diff line number Diff line change
Expand Up @@ -1638,6 +1638,9 @@ The paths themselves are given in the direction of the first geometry.</p>
<li>S: has spatial reference system</li>
</ul>
</span></td></tr>
<tr><td><a name="st_symdifference"></a><code>st_symdifference(geometry_a: geometry, geometry_b: geometry) &rarr; geometry</code></td><td><span class="funcdesc"><p>Returns the symmetric difference of both geometries.</p>
<p>This function utilizes the GEOS module.</p>
</span></td></tr>
<tr><td><a name="st_touches"></a><code>st_touches(geometry_a: geometry, geometry_b: geometry) &rarr; <a href="bool.html">bool</a></code></td><td><span class="funcdesc"><p>Returns true if the only points in common between geometry_a and geometry_b are on the boundary. Note points do not touch other points.</p>
<p>This function utilizes the GEOS module.</p>
<p>This function variant will attempt to utilize any available geospatial index.</p>
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14 changes: 13 additions & 1 deletion pkg/geo/geomfn/topology_operations.go
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Expand Up @@ -66,7 +66,7 @@ func Intersection(a geo.Geometry, b geo.Geometry) (geo.Geometry, error) {
return geo.ParseGeometryFromEWKB(retEWKB)
}

// Union returns the geometries of intersection between A and B.
// Union returns the geometries of union between A and B.
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thanks!

func Union(a geo.Geometry, b geo.Geometry) (geo.Geometry, error) {
if a.SRID() != b.SRID() {
return geo.Geometry{}, geo.NewMismatchingSRIDsError(a.SpatialObject(), b.SpatialObject())
Expand All @@ -78,6 +78,18 @@ func Union(a geo.Geometry, b geo.Geometry) (geo.Geometry, error) {
return geo.ParseGeometryFromEWKB(retEWKB)
}

// SymDifference returns the geometries of symmetric difference between A and B.
func SymDifference(a geo.Geometry, b geo.Geometry) (geo.Geometry, error) {
if a.SRID() != b.SRID() {
return geo.Geometry{}, geo.NewMismatchingSRIDsError(a.SpatialObject(), b.SpatialObject())
}
retEWKB, err := geos.SymDifference(a.EWKB(), b.EWKB())
if err != nil {
return geo.Geometry{}, err
}
return geo.ParseGeometryFromEWKB(retEWKB)
}

// SharedPaths Returns a geometry collection containing paths shared by the two input geometries.
func SharedPaths(a geo.Geometry, b geo.Geometry) (geo.Geometry, error) {
if a.SRID() != b.SRID() {
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26 changes: 26 additions & 0 deletions pkg/geo/geomfn/topology_operations_test.go
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Expand Up @@ -183,6 +183,32 @@ func TestUnion(t *testing.T) {
})
}

func TestSymDifference(t *testing.T) {
testCases := []struct {
a geo.Geometry
b geo.Geometry
expected geo.Geometry
}{
{rightRect, rightRect, emptyRect},
{leftRect, rightRect, geo.MustParseGeometry("POLYGON((0 0, -1 0, -1 1, 0 1, 1 1, 1 0, 0 0))")},
{leftRect, overlappingRightRect, geo.MustParseGeometry("MULTIPOLYGON(((-0.1 0, -1 0, -1 1, -0.1 1, -0.1 0)), ((0 0, 0 1, 1 1, 1 0, 0 0)))")},
{rightRect, rightRectPoint, geo.MustParseGeometry("POLYGON((0 0, 0 1, 1 1, 1 0, 0 0))")},
}

for i, tc := range testCases {
t.Run(fmt.Sprintf("tc:%d", i), func(t *testing.T) {
g, err := SymDifference(tc.a, tc.b)
require.NoError(t, err)
require.Equal(t, tc.expected, g)
})
}

t.Run("errors if SRIDs mismatch", func(t *testing.T) {
_, err := SymDifference(mismatchingSRIDGeometryA, mismatchingSRIDGeometryB)
requireMismatchingSRIDError(t, err)
})
}

func TestSharedPaths(t *testing.T) {
type args struct {
a geo.Geometry
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31 changes: 31 additions & 0 deletions pkg/geo/geos/geos.cc
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Expand Up @@ -100,6 +100,8 @@ typedef CR_GEOS_Geometry (*CR_GEOS_ConvexHull_r)(CR_GEOS_Handle, CR_GEOS_Geometr
typedef CR_GEOS_Geometry (*CR_GEOS_Union_r)(CR_GEOS_Handle, CR_GEOS_Geometry, CR_GEOS_Geometry);
typedef CR_GEOS_Geometry (*CR_GEOS_Intersection_r)(CR_GEOS_Handle, CR_GEOS_Geometry,
CR_GEOS_Geometry);
typedef CR_GEOS_Geometry (*CR_GEOS_SymDifference_r)(CR_GEOS_Handle, CR_GEOS_Geometry,
CR_GEOS_Geometry);
typedef CR_GEOS_Geometry (*CR_GEOS_PointOnSurface_r)(CR_GEOS_Handle, CR_GEOS_Geometry);

typedef CR_GEOS_Geometry (*CR_GEOS_Interpolate_r)(CR_GEOS_Handle, CR_GEOS_Geometry, double);
Expand Down Expand Up @@ -185,6 +187,7 @@ struct CR_GEOS {
CR_GEOS_Union_r GEOSUnion_r;
CR_GEOS_PointOnSurface_r GEOSPointOnSurface_r;
CR_GEOS_Intersection_r GEOSIntersection_r;
CR_GEOS_SymDifference_r GEOSSymDifference_r;

CR_GEOS_Interpolate_r GEOSInterpolate_r;

Expand Down Expand Up @@ -266,6 +269,7 @@ struct CR_GEOS {
INIT(GEOSUnion_r);
INIT(GEOSPointOnSurface_r);
INIT(GEOSIntersection_r);
INIT(GEOSSymDifference_r);
INIT(GEOSInterpolate_r);
INIT(GEOSDistance_r);
INIT(GEOSCovers_r);
Expand Down Expand Up @@ -798,6 +802,33 @@ CR_GEOS_Status CR_GEOS_Intersection(CR_GEOS* lib, CR_GEOS_Slice a, CR_GEOS_Slice
return toGEOSString(error.data(), error.length());
}

CR_GEOS_Status CR_GEOS_SymDifference(CR_GEOS* lib, CR_GEOS_Slice a, CR_GEOS_Slice b,
CR_GEOS_String* symdifferenceEWKB) {
std::string error;
auto handle = initHandleWithErrorBuffer(lib, &error);
*symdifferenceEWKB = {.data = NULL, .len = 0};

auto geomA = CR_GEOS_GeometryFromSlice(lib, handle, a);
auto geomB = CR_GEOS_GeometryFromSlice(lib, handle, b);
if (geomA != nullptr && geomB != nullptr) {
auto symdifferenceGeom = lib->GEOSSymDifference_r(handle, geomA, geomB);
if (symdifferenceGeom != nullptr) {
auto srid = lib->GEOSGetSRID_r(handle, geomA);
CR_GEOS_writeGeomToEWKB(lib, handle, symdifferenceGeom, symdifferenceEWKB, srid);
lib->GEOSGeom_destroy_r(handle, symdifferenceGeom);
}
}
if (geomA != nullptr) {
lib->GEOSGeom_destroy_r(handle, geomA);
}
if (geomB != nullptr) {
lib->GEOSGeom_destroy_r(handle, geomB);
}

lib->GEOS_finish_r(handle);
return toGEOSString(error.data(), error.length());
}

//
// Linear Reference
//
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13 changes: 13 additions & 0 deletions pkg/geo/geos/geos.go
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Expand Up @@ -417,6 +417,19 @@ func Union(a geopb.EWKB, b geopb.EWKB) (geopb.EWKB, error) {
return cStringToSafeGoBytes(cEWKB), nil
}

// SymDifference returns an EWKB which is the symmetric difference of shapes A and B.
func SymDifference(a geopb.EWKB, b geopb.EWKB) (geopb.EWKB, error) {
g, err := ensureInitInternal()
if err != nil {
return nil, err
}
var cEWKB C.CR_GEOS_String
if err := statusToError(C.CR_GEOS_SymDifference(g, goToCSlice(a), goToCSlice(b), &cEWKB)); err != nil {
return nil, err
}
return cStringToSafeGoBytes(cEWKB), nil
}

// InterpolateLine returns the point along the given LineString which is at
// a given distance from starting point.
// Note: For distance less than 0 it returns start point similarly for distance
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2 changes: 2 additions & 0 deletions pkg/geo/geos/geos.h
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Expand Up @@ -103,6 +103,8 @@ CR_GEOS_Status CR_GEOS_PointOnSurface(CR_GEOS* lib, CR_GEOS_Slice a,
CR_GEOS_String* pointOnSurfaceEWKB);
CR_GEOS_Status CR_GEOS_Intersection(CR_GEOS* lib, CR_GEOS_Slice a, CR_GEOS_Slice b,
CR_GEOS_String* intersectionEWKB);
CR_GEOS_Status CR_GEOS_SymDifference(CR_GEOS* lib, CR_GEOS_Slice a, CR_GEOS_Slice b,
CR_GEOS_String* symdifferenceEWKB);
CR_GEOS_Status CR_GEOS_SharedPaths(CR_GEOS* lib, CR_GEOS_Slice a, CR_GEOS_Slice b, CR_GEOS_String* ret);

//
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