postgis - Polygons have holes after pgr_pointsAsPolygon

I calculate a 500m Isochrones with pgr_drivingDistance and after that use pgr_pointsAsPolygon to create the Isochrones out of the resulting nodes.

SELECT * FROM pgr_pointsAsPolygon('SELECT id,x,y FROM Calc_nodes')

Sadly in some case the Dijkstra algorithm create holes in the resulting poylgons. I know the reason for this is the nature of the network and how the algorithm works.

I just need function to check if there are holes and then get rid of them. Any suggestions?

Answer

Try

SELECT ST_MakePolygon(ST_ExteriorRing()) AS geom
FROM 

to process all polygons, or

SELECT CASE
         WHEN ST_NRings() > 1
         THEN ST_MakePolygon(ST_ExteriorRing())

         ELSE 
       END AS geom
FROM 

to only process those with an interior ring.