3

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

  • It seems that your polygons are of XYM or XYZM type but ST_MakeValid does not keep the M (measure) dimension. It is documented in postgis.net/docs/ST_MakeValid.html that 3d is supported but there is no mention about M. Do you really need M or could you convert your data into XY or XYZ? – user30184 Dec 12 '16 at 7:10
  • I don't need M at all – the_darkside Dec 12 '16 at 7:15
  • In that case I think it would be easiest to copy the whole table into a new one and drop M with some of the methods from the list of gis.stackexchange.com/questions/221052/…. If you are a beginner then I recommend using ogr2ogr with -dim XY because it takes automatically care of spatial index and updating geometry_columns. – user30184 Dec 12 '16 at 7:28
6

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.

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