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 ](https://aws.amazon.com/blogs/big-data/amazon-redshift-python-user-defined-functions-will-reach-end-of-support-after-june-30-2026/) that was published on June 30, 2025. 

# ST\_InteriorRingN
<a name="ST_InteriorRingN-function"></a>

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
<a name="ST_InteriorRingN-function-syntax"></a>

```
ST_InteriorRingN(geom, index)
```

## Arguments
<a name="ST_InteriorRingN-function-arguments"></a>

 *geom*   
A value of data type `GEOMETRY` or an expression that evaluates to a `GEOMETRY` type. 

 *index*   
A value of data type `INTEGER` that represents the position of a ring of a one-based index. 

## Return type
<a name="ST_InteriorRingN-function-return"></a>

`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
<a name="ST_InteriorRingN-function-examples"></a>

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)
```