H2GIS

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ST_IsValidDetail

Signatures

ARRAY ST_IsValidDetail(GEOMETRY geom);
ARRAY ST_IsValidDetail(GEOMETRY geom, INT selfTouchValid);

Description

Returns an H2 ARRAY containing 3 elements describing whether geom is valid:

  1. A BOOLEAN stating whether geom is valid or not
  2. The reason why
  3. The error location, or NULL if geom is valid

Optional variable selfTouchValid sets whether polygons using self-touching rings to form holes are reported as valid. If this flag is set, the following self-touching conditions are treated as being valid:

  • The shell ring self-touches to create a hole touching the shell
  • A hole ring self-touches to create two holes touching at a point

The default of 0 (following the OGC SFS standard) is that this condition is not valid. Set it to 1 to consider it valid (c.f. ESRI SDE model).

Examples

SELECT ST_IsValidDetail('POLYGON((210 440, 134 235, 145 233,
                                  310 200, 340 360, 210 440))');
-- Answer: (TRUE, Valid Geometry, NULL)

SELECT ST_IsValidDetail(
            'POLYGON((0 0 1, 10 0 1, 10 5 1, 6 -2 1, 0 0 1))');
-- Answer: (FALSE, Self-intersection, POINT(7.142857142857143 0 1))

SELECT ST_IsValidDetail('POLYGON((1 1, 1 6, 5 1, 1 1),
                                 (3 4, 3 5, 4 4, 3 4))');
-- Answer: (FALSE, Hole lies outside shell, POINT(3 4))

-- The next two examples show that the validation model we choose
-- is important.
SELECT ST_IsValidDetail(
            'POLYGON((3 0, 0 3, 6 3, 3 0, 4 2, 2 2, 3 0))', 0);
-- Answer: (FALSE, Ring Self-intersection, POINT(3 0))

SELECT ST_IsValidDetail(
            'POLYGON((3 0, 0 3, 6 3, 3 0, 4 2, 2 2, 3 0))', 1);
-- Answer: (TRUE, Valid Geometry, NULL)

See also