I expected to get 'false' from the following statement:

SELECT ST_IsValid(ST_GeomFromText('POLYGON((0 0,10 0,10 10,10 10,0 10,0 0))'));

Instead it returns true! Even if the vertex in 10,10 is followed by another one with the same coordinates. Maybe I misunderstood something and/or I am making some mistake. Where can I find a complete explain of that makes a geometry not valid?


The canonical definition of geometry validity is the OGC Simple Feature Access for SQL standard.

There is also the PostGIS documentation, although it is more descriptive than formal.

In short, repeated points are valid. This is defined implicitly in the above references. It certainly wouldn't hurt to make it explicit in the PostGIS doc.

  • Thank You, It was very helpful! – Jacopo Russo Sep 9 '19 at 11:39

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