when I try to makemigrate models with Geometry fields to postgres DB I face with next message:

You are trying to change the nullable field 'geom' on allotment to non-nullable without a default; we can't do that (the database needs something to populate existing rows).

OK, set default = ' ', or something like 'MULTIPOLIGON (((0. 0. 0. 0. 0.)))' and when I wish to migrate terminal throws this:

    ..File "/home/user/MyProjects/forest-venv/lib/python3.5/site-packages/django/contrib/gis/geos/geometry.py", line 697, in __init__
    raise ValueError('String input unrecognized as WKT EWKT, and HEXEWKB.')
ValueError: String input unrecognized as WKT EWKT, and HEXEWKB.

An examples of my classes with geometry:

class ForestryKeys(models.Model):

id = models.IntegerField(primary_key=True)
name = models.TextField(blank=True, null=True), 
geom = models.MultiPolygonField(verbose_name='geo',srid = 4326)

class Meta:
    managed = True
    verbose_name = 'geo'
    verbose_name_plural =  'geos'

class DistrForestKeys(models.Model):

id = models.IntegerField(primary_key=True)
df_names = models.TextField(blank=True, null=True)
geom = models.MultiPolygonField(verbose_name='polygs',srid = 4326)
forestry_id = models.ForeignKey(ForestryKeys, models.DO_NOTHING, blank=True, null=True)

class Meta:
    managed = True
    verbose_name = 'ULV'
    verbose_name_plural =  'ULVs'


Why I have to set default value? and how it do correct for diffrient geometry types?


Your problem should disappear if you allow the geometry field to be null like this:

geom = models.MultiPolygonField(verbose_name='geo',srid = 4326, null=True, blank=True)

If you prefer a non-nullable field, use a valid default. Your multipolygon declaration is not valid WKT as the error states.

  • You have a typo in the type name (multipolygon vs multipoligon)
  • You need to describe a full polygon in your default

Try using an empty polygon


or a valid dummy polygon

"MULTIPOLYGON (((0 0, 0 1, 1 1, 1 0, 0 0)))"
| improve this answer | |
  • my code started work after set geographu = True – Tyomik_mnemonic Mar 13 '19 at 11:09

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