DO $$
DECLARE
v_boundaryUnion     geometry;
v_unitBoundary      geometry;

BEGIN
SELECT ST_Union(b."Geometry")
    INTO v_boundaryUnion
    FROM myschema."Boundary" a
    INNER JOIN myschema."BoundaryGeom" b
        ON b."BoundaryId" = a."BoundaryId"
    WHERE a."UnitId" = 1;

RAISE NOTICE 'BOUNDARY UNION: %', ST_AsText(v_boundaryUnion);


SELECT ST_Boundary("Geometry")
    INTO v_unitBoundary
    FROM myschema."UnitGeom"
    WHERE "UnitId" = 1;

RAISE NOTICE 'UNION BOUNDARY: %', ST_AsText(v_unitBoundary);


IF ST_Equals(v_boundaryUnion, v_unitBoundary) THEN
    RAISE NOTICE 'EQUALS';
ELSE
    RAISE NOTICE 'DIFFERENCE';
END IF;

v_boundaryUnion := ST_GeomFromWKB(ST_AsBinary(v_boundaryUnion), 3765);
RAISE NOTICE 'UNION FROM WKB: %', ST_AsText(v_boundaryUnion);

IF ST_Equals(v_boundaryUnion, v_unitBoundary) THEN
    RAISE NOTICE 'EQUALS';
ELSE
    RAISE NOTICE 'DIFFERENCE';
END IF;


v_boundaryUnion := ST_GeomFromText(ST_AsText(v_boundaryUnion), 3765);
RAISE NOTICE 'UNION FROM WKT: %', ST_AsText(v_boundaryUnion);

IF ST_Equals(v_boundaryUnion, v_unitBoundary) THEN
    RAISE NOTICE 'EQUALS';
ELSE
    RAISE NOTICE 'DIFFERENCE';
END IF;

END $$;

f_table_name, f_geometry_column, coord_dimension, srid, type
"UnitGeom";"Geometry";2;3765;"GEOMETRY"
"BoundaryGeom";"Geometry";2;3765;"LINESTRING"