SDO_LRS.REVERSE

Format

SDO_LRS.REVERSE_GEOMETRY(
     geom         IN SDO_GEOMETRY 
     [, dim_array IN SDO_DIM_ARRAY] 
     ) RETURN SDO_GEOMETRY;

Description

Returns a new geometric segment by reversing the measure values and the direction of the original geometric segment.

Parameters

geom: Geometric segment (LRS segment) containing measure information.
dim_array: Dimensional information array corresponding to geom, 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

That is, the start measure of geom is the end measure of the returned geometric segment, the end measure of geom is the start measure of the returned geometric segment, and all other measures are adjusted accordingly.
Reverses the direction of geom

Compare this function with SDO_LRS.REVERSE_MEASURE, which reverses only the measure values (not the direction) of a geometric segment.

To reverse the vertices of a non-LRS line string geometry, use the SDO_UTIL.REVERSE_LINESTRING function, which is described in SDO_LRS Package (Linear Referencing System).

An exception is raised if geom has an invalid geometry type or dimensionality. The geometry type must be a line or multiline, and the dimensionality must be 3 (two dimensions plus the measure dimension).

The _3D format of this function (SDO_LRS.REVERSE_GEOMETRY_3D) is available. For information about _3D formats of LRS functions, see 3D Formats of LRS Functions.

Examples

The following example reverses the measure values and the direction of the geometric segment representing Route 1. (This example uses the definitions from the example in Example of LRS Functions.)

-- Reverse direction and measures (for example, to prepare for
-- concatenating with another road).
-- 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_GEOMETRY(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_GEOMETRY(A.ROUTE_GEOMETRY,M.DIMINFO)(SDO_GTYPE, SDO_SRID, SDO_PO
--------------------------------------------------------------------------------
SDO_GEOMETRY(3302, NULL, NULL, SDO_ELEM_INFO_ARRAY(1, 2, 1), SDO_ORDINATE_ARRAY(
5, 14, 27, 8, 10, 22, 12, 10, 18, 12, 4, 12, 8, 4, 8, 2, 4, 2, 2, 2, 0))

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