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ST_Reverse3DLine

Signatures

GEOMETRY ST_Reverse3DLine(GEOMETRY geom);
GEOMETRY ST_Reverse3DLine(GEOMETRY geom, VARCHAR sortOrder);

Description

Potentially reverses geom according to the z-values of its first and last coordinates and the optional parameter sortOrder, which can take the following values:

Value Meaning
asc ascending (default value)
desc descending

Returns geom untouched if the start or end coordinate has no z-value.

Only the first and last coordinates are considered.

Intermediate z-values have no effect on the sorting.

Returns NULL if geom is not a LINESTRING or a MULTILINESTRING.

Examples

-- Reverses the order since the default value of sortOrder is asc
-- and 10 > 0:
SELECT ST_Reverse3DLine(
            'LINESTRING(105 353 10, 150 180, 300 280 0)');
-- Answer:   LINESTRING(300 280 0, 150 180, 105 353 10)

-- Makes no change since the LINESTRING is already in descending
-- order:
SELECT ST_Reverse3DLine(
            'LINESTRING(105 353 10, 150 180, 300 280 0)', 'desc');
-- Answer:   LINESTRING(105 353 10, 150 180, 300 280 0)

-- Puts the LINESTRING in descending order:
SELECT ST_Reverse3DLine(
            'LINESTRING(105 353 0, 150 180, 300 280 10)', 'desc');
-- Answer:   LINESTRING(300 280 10, 150 180, 105 353 0)

-- Puts each component LINESTRING in descending order:
SELECT ST_Reverse3DLine(
            'MULTILINESTRING((1 1 1, 1 6 2, 2 2 1, -1 2 3),
                             (1 2 0, 4 2, 4 6 2))', 'desc');
-- Answer:   MULTILINESTRING((-1 2 3, 2 2 1, 1 6 2, 1 1 1),
--                           (4 6 2, 4 2, 1 2 0))
Non-examples
-- Returns the Geometry untouched since its first coordinate
-- contains no z-value:
SELECT ST_Reverse3DLine('LINESTRING(1 1, 1 6 2, 2 2, -1 2 3)');
-- Answer:               LINESTRING(1 1, 1 6 2, 2 2, -1 2 3)

-- Returns NULL for Geometries other than LINESTRINGs and
-- MULTILINESTRINGs:
SELECT ST_Reverse3DLine('POLYGON((190 300, 140 180, 300 110,
                                  313 117, 430 270, 190 300))');
-- Answer: NULL
See also