# Parcel duplicate repair

* adds mechanic to repair parcels in case of unwanted parcel duplicates
* optimizes filtering of geometries for parcel recalculation

konova/models/parcel.py

@@ -5,7 +5,7 @@ Contact: michel.peltriaux@sgdnord.rlp.de
 Created on: 16.12.21
 
 """
-from django.db import models
+from django.db import models, transaction
 
 from konova.models import UuidModel
 
@@ -158,6 +158,46 @@ class Parcel(UuidModel):
     def __str__(self):
         return f"{self.parcel_group} | {self.flr} | {self.flrstck_zhlr} | {self.flrstck_nnr}"
 
+    @classmethod
+    @transaction.atomic
+    def make_unique(cls, **kwargs):
+        """ Checks for duplicates of a Parcel, choose a (now) unique one,
+        repairs relations for ParcelIntersection and removes duplicates.
+
+        Args:
+            **kwargs ():
+
+        Returns:
+            unique_true (Parcel): The new unique 'true one'
+        """
+        parcel_objs = Parcel.objects.filter(**kwargs)
+
+        if not parcel_objs.exists():
+            return None
+
+        # Get one of the found parcels and use it as new 'true one'
+        unique_parcel = parcel_objs.first()
+        # separate it from the rest
+        parcel_objs = parcel_objs.exclude(id=unique_parcel.id)
+
+        if not parcel_objs.exists():
+            # There are no duplicates - all good, just return
+            return unique_parcel
+
+        # Fetch existing intersections, which still point on the duplicated parcels
+        intersection_objs = ParcelIntersection.objects.filter(
+            parcel__in=parcel_objs
+        )
+        # Change each intersection, so they point on the 'true one' parcel from now on
+        for intersection in intersection_objs:
+            intersection.parcel = unique_parcel
+            intersection.save()
+
+        # Remove the duplicated parcels
+        parcel_objs.delete()
+
+        return unique_parcel
+
 
 class ParcelIntersection(UuidModel):
     """