Amazon Redshift will no longer support the use of Python UDFs after June 30, 2026.
We will start enforcing it in phases. For more information on the details of Python end of life
and migration options, see the
blog post
ST_InteriorRingN
ST_InteriorRingN returns a closed linestring corresponding to the interior ring of an input polygon at the index position. The dimension of the returned geometry is the same as that of the input geometry.
Syntax
ST_InteriorRingN(geom, index)
Arguments
- geom
-
A value of data type
GEOMETRYor an expression that evaluates to aGEOMETRYtype. - index
-
A value of data type
INTEGERthat represents the position of a ring of a one-based index.
Return type
GEOMETRY of subtype LINESTRING.
The spatial reference system identifier (SRID) value of the returned geometry is the SRID value of the input geometry.
If geom or index is null, then null is returned.
If index is out of range, then null is returned.
If geom is not a polygon, then null is returned.
If geom is an empty polygon, then null is returned.
Examples
The following SQL returns the second ring of the polygon as a closed linestring.
SELECT ST_AsEWKT(ST_InteriorRingN(ST_GeomFromText('POLYGON((7 9,8 7,11 6,15 8,16 6,17 7,17 10,18 12,17 14,15 15,11 15,10 13,9 12,7 9),(9 9,10 10,11 11,11 10,10 8,9 9),(12 14,15 14,13 11,12 14))'),2));
st_asewkt
-----------
LINESTRING(12 14,15 14,13 11,12 14)