STV_Reverse

Reverses the order of the vertices of a spatial object.

Behavior type

Syntax

STV_Reverse( g, [USING PARAMETERS skip_nonreorientable_polygons={true | false} ])

Arguments

g

Spatial object, type GEOGRAPHY.

skip_nonreorientable_polygons = { true | false }

(Optional) Boolean

When set to False, non-orientable polygons generate an error. For example, if you use STV_ForceLHR or STV_Reverse with skip_nonorientable_polygons set to False, a geography polygon containing a hole generates an error. When set to True, the result returned is the polygon, as passed to the API, without alteration.

This argument can help you when you are creating an index from a table containing polygons that cannot be re-oriented.

Vertica Place considers these polygons non-orientable:

• Polygons with a hole

• Multipolygons

• Multipolygons with a hole

Default value: False

Returns

GEOGRAPHY

Supported data types

Examples

The following examples show how you can use STV_Reverse.

Reverse vertices of a geography polygon:

=> SELECT ST_AsText(STV_Reverse(ST_GeographyFromText('Polygon((1 1, 3 1, 2 2, 1 1))')));
            ST_AsText
--------------------------------
 POLYGON ((1 1, 2 2, 3 1, 1 1))
(1 row)

Force the polygon to reverse orientation:

=> SELECT ST_AsText(STV_Reverse(ST_GeographyFromText('Polygon((1 1, 2 2, 3 1, 1 1))')));
ST_AsText
--------------------------------
 POLYGON ((1 1, 3 1, 2 2, 1 1))
(1 row)

See also