OGCGeometry#union of geometries of different dimensions is incorrect

I’m seeing incorrect results when calling OGCGeometry#union on geometries of different dimensions, e.g. point and linestring, linestring and polygon, etc.

For example, the following tests

public class TestOGCUnion
{
    @Test
    public void testPoint()
    {
        assertUnion("POINT (1 2)", "LINESTRING EMPTY", "POINT (1 2)");
    }

    @Test
    public void testPointWithLinestring()
    {
        assertUnion("POINT (1 2)", "LINESTRING (3 4, 5 6)", "GEOMETRYCOLLECTION (POINT (1 2), LINESTRING (3 4, 5 6))");
    }

    @Test
    public void testLinestring()
    {
        assertUnion("LINESTRING (1 2, 3 4)", "POLYGON EMPTY", "LINESTRING (1 2, 3 4)");
    }

    @Test
    public void testLinestringWithPolygon()
    {
        assertUnion("LINESTRING (1 2, 3 4)", "POLYGON ((0 0, 1 1, 0 1, 0 0))", "GEOMETRYCOLLECTION (LINESTRING (1 2, 3 4), POLYGON ((0 0, 1 1, 0 1, 0 0)))");
    }

    private void assertUnion(String leftWkt, String rightWkt, String expectedWkt)
    {
        OGCGeometry union = OGCGeometry.fromText(leftWkt).union(OGCGeometry.fromText(rightWkt));
        assertEquals(expectedWkt, union.asText());
    }
}

fail with

Expected :POINT (1 2)
Actual   :MULTILINESTRING EMPTY

  at com.esri.core.geometry.TestOGCUnion.testPoint(TestOGCUnion.java:26)

Expected :GEOMETRYCOLLECTION (POINT (1 2), LINESTRING (3 4, 5 6))
Actual   :LINESTRING (3 4, 5 6)

  at com.esri.core.geometry.TestOGCUnion.testPointWithLinestring(TestOGCUnion.java:32)

Expected :LINESTRING (1 2, 3 4)
Actual   :MULTIPOLYGON EMPTY

  at com.esri.core.geometry.TestOGCUnion.testLinestring(TestOGCUnion.java:38)

Expected :GEOMETRYCOLLECTION (LINESTRING (1 2, 3 4), POLYGON ((0 0, 1 1, 0 1, 0 0)))
Actual   :POLYGON ((0 0, 1 1, 0 1, 0 0))

  at com.esri.core.geometry.TestOGCUnion.testLinestringWithPolygon(TestOGCUnion.java:44)

I’m also seeing union of POLYGON ((0 0, 1 1, 0 1, 0 0)) and POLYGON ((0.5 0.5, 0.7 0.7, 0.5 0.7, 0.5 0.5)) being POLYGON ((0.7 0.7, 1 1, 0 1, 0 0, 0.5 0.5, 0.7 0.7)) and not POLYGON ((0 0, 1 1, 0 1, 0 0)). The shapes are the same, but union result has redundant points. Is this expected?

[mbasmanova]

@jgravois John, thanks for explaining. @stolstov Looks like Sergey’s PR https://github.com/Esri/geometry-api-java/pull/178 improves union method to perform simplification inline. With these change, we’ll be able to use union in Presto directly.

[stolstov]

@mbasmanova Nothing else, unless you would like to do more verification.