Validating geometries in PostGIS

Question

I am trying to validate the geometry of all polygons in my table.

When I perform the following query, I get an error:

update parcel2016
set geom = St_MakeValid(geom)

ERROR:  Column has M dimension but geometry does not
********** Error **********

ERROR: Column has M dimension but geometry does not
SQL state: 22023

How might this be corrected? I've also tried wrapping in:

set geom = st_multi(st_collectionextract(st_makevalid(geom)))

but this was equally unsuccessful

Answer 1

Without knowing what the full dimensionality of your data are (XYZM or just XYM) I cannot give a perfect answer, but assuming you have the more common XYZM you can strip the M dimension before running the ST_MakeValid(). Hopefully the M isn't important to you...

ALTER TABLE mytable 
  ALTER COLUMN geom 
  TYPE geometry(polygonz, 4326) 
  USING ST_Force3DZ(geom)

You'll have to fill in the geometry type and SRID number that make sense for your table.