Question: I deal with forest inventory geodatabase that contains a lot of polygons.
Those polygons come from some software that allows topologically incorrect data.
So I should check the polygons.
Performing the following query

```
select * from world_kvrtpolygon where st_isvalid(mpoly)

```

I got errors in cases that do not seem to be incorrect (see picture)
[![enter image description here](https://i.stack.imgur.com/9ZdQp.png)](https://i.stack.imgur.com/9ZdQp.png)

This case occurs when parts of a polygon connect by one point.

Is there a way to ignore such cases?
Or how to deal with such cases.

Answer: 
Accordng to the OGC Simple Features geometry model used by PostGIS, the rings in polygons must not self-intersect. Obviously, a polygon with a self-intersection forming a "pinch point" is invalid under this definition.

As another answer suggested, use `ST_MakeValid` to convert this to a `MultiPolygon`.
You can make a multi-polygon or split the source to two polygons. Have a look at [`st_makeValid`](https://postgis.net/docs/ST_MakeValid.html), which *"Single polygons may become multi-geometries in case of self-intersections."*

```sql
select st_asText(St_makeValid('POLYGON((0 0, 10 0, 0 10, 10 10, 0 0))'));
                         st_astext
-----------------------------------------------------------
 MULTIPOLYGON(((5 5,10 0,0 0,5 5)),((5 5,0 10,10 10,5 5)))

```