SDO_LRS.REVERSE

Format

SDO_LRS.REVERSE_MEASURE(
     geom_segment IN SDO_GEOMETRY 
     [, dim_array IN SDO_DIM_ARRAY] 
     ) RETURN SDO_GEOMETRY;

Description

Returns a new geometric segment by reversing the measure values, but not the direction, of the original geometric segment.

Parameters

geom_segment: Geometric segment (LRS segment) containing measure information.
dim_array: Dimensional information array corresponding to geom_segment, usually selected from one of the xxx_SDO_GEOM_METADATA views (described in Geometry Metadata Views).

Usage Notes

This function:

Reverses the measure values of geom_segment

That is, the start measure of geom_segment is the end measure of the returned geometric segment, the end measure of geom_segment is the start measure of the returned geometric segment, and all other measures are adjusted accordingly.
Does not affect the direction of geom_segment

Compare this function with SDO_LRS.REVERSE_GEOMETRY, which reverses both the direction and the measure values of a geometric segment.

An exception is raised if geom_segment has an invalid geometry type or dimensionality.

The _3D format of this function (SDO_LRS.REVERSE_MEASURE_3D) is available. For information about _3D formats of LRS functions, see 3D Formats of LRS Functions.

Note:

The behavior of the SDO_LRS.REVERSE_MEASURE function changed after release 8.1.7. In release 8.1.7, REVERSE_MEASURE reversed both the measures and the segment direction. However, if you want to have this same behavior with subsequent releases, you must use the SDO_LRS.REVERSE_GEOMETRY function.

Examples

The following example reverses the measure values of the geometric segment representing Route 1, but does not affect the direction. (This example uses the definitions from the example in Example of LRS Functions.)

-- First, display the original segment; then, reverse.
SELECT a.route_geometry FROM lrs_routes a WHERE a.route_id = 1;

ROUTE_GEOMETRY(SDO_GTYPE, SDO_SRID, SDO_POINT(X, Y, Z), SDO_ELEM_INFO, SDO_ORDIN
--------------------------------------------------------------------------------
SDO_GEOMETRY(3302, NULL, NULL, SDO_ELEM_INFO_ARRAY(1, 2, 1), SDO_ORDINATE_ARRAY(
2, 2, 0, 2, 4, 2, 8, 4, 8, 12, 4, 12, 12, 10, 18, 8, 10, 22, 5, 14, 27))        
                                                                                

SELECT SDO_LRS.REVERSE_MEASURE(a.route_geometry, m.diminfo)
  FROM lrs_routes a, user_sdo_geom_metadata m
  WHERE m.table_name = 'LRS_ROUTES' AND m.column_name = 'ROUTE_GEOMETRY'
    AND a.route_id = 1;

SDO_LRS.REVERSE_MEASURE(A.ROUTE_GEOMETRY,M.DIMINFO)(SDO_GTYPE, SDO_SRID, SDO_POI
--------------------------------------------------------------------------------
SDO_GEOMETRY(3302, NULL, NULL, SDO_ELEM_INFO_ARRAY(1, 2, 1), SDO_ORDINATE_ARRAY(
2, 2, 27, 2, 4, 25, 8, 4, 19, 12, 4, 15, 12, 10, 9, 8, 10, 5, 5, 14, 0))

Note in the returned segment that the M values (measures) now go in descending order from 27 to 0, but the segment start and end points have the same X and Y values as in the original segment (2,2 and 5,14).