ST_ISCLOSED

SinceVersion dev

Description

Determines whether a LINESTRING is closed. A LINESTRING is closed when its first and last points are exactly equal. This function does not use a distance tolerance.

Syntax

ST_ISCLOSED( <shape> )

Parameters

Parameter	Description
<shape>	An encoded geometry value (VARCHAR) returned by a spatial constructor such as ST_GeometryFromText or ST_LineFromText. Raw WKT text must first be converted with a constructor.

Return Value

Returns a BOOLEAN value:

• true if the input is a valid LINESTRING whose first and last points are exactly equal.
• false if the input is a valid LINESTRING whose first and last points are different.
• NULL if the input is NULL, is not a LINESTRING, or cannot be decoded as a valid geometry.

In SQL output, true is displayed as 1 and false as 0.

Example

Closed LineString

SELECT ST_IsClosed(
    ST_GeometryFromText('LINESTRING(0 0, 1 1, 0 0)')
) AS is_closed;

+-----------+
| is_closed |
+-----------+
|         1 |
+-----------+

Open LineString

SELECT ST_IsClosed(
    ST_GeometryFromText('LINESTRING(0 0, 1 1)')
) AS is_closed;

+-----------+
| is_closed |
+-----------+
|         0 |
+-----------+

NULL Input

SELECT ST_IsClosed(NULL) AS is_closed;

+-----------+
| is_closed |
+-----------+
|      NULL |
+-----------+

Non-LineString Input

SELECT ST_IsClosed(ST_Point(0, 0)) AS is_closed;

+-----------+
| is_closed |
+-----------+
|      NULL |
+-----------+