ST_IsSimple

Introduction: Test if geometry's only self-intersections are at boundary points.

Format: ST_IsSimple (A: Geometry)

Return type: Boolean

Since: v1.3.0

Example:

SELECT ST_IsSimple(ST_GeomFromWKT('POLYGON((1 1, 3 1, 3 3, 1 3, 1 1))'))

Output:

true