Amazon Redshift will no longer support the creation of new Python UDFs starting Patch 198. Existing Python UDFs will continue to function until June 30, 2026. For more information, 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/). 

# ST\$1InteriorRingN
<a name="ST_InteriorRingN-function"></a>

ST\$1InteriorRingN 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)
```