Exclude indexs when delete unique constrains

sql_server/pyodbc/schema.py

@@ -2,10 +2,16 @@
 import datetime
 
 from django.db.backends.base.schema import (
-    BaseDatabaseSchemaEditor, logger, _is_relevant_relation, _related_non_m2m_objects,
+    BaseDatabaseSchemaEditor,
+    _is_relevant_relation,
+    _related_non_m2m_objects,
+    logger,
 )
 from django.db.backends.ddl_references import (
-    Columns, IndexName, Statement as DjStatement, Table,
+    Columns,
+    IndexName,
+    Statement as DjStatement,
+    Table,
 )
 from django.db.models import Index
 from django.db.models.fields import AutoField, BigAutoField
@@ -935,7 +941,8 @@ def remove_field(self, model, field):
                 })
         # Drop unique constraints, SQL Server requires explicit deletion
         for name, infodict in constraints.items():
-            if field.column in infodict['columns'] and infodict['unique'] and not infodict['primary_key']:
+            if (field.column in infodict['columns'] and infodict['unique'] and
+                    not infodict['primary_key'] and not infodict['index']):
                 self.execute(self.sql_delete_unique % {
                     "table": self.quote_name(model._meta.db_table),
                     "name": self.quote_name(name),

testapp/migrations/0006_test_remove_onetoone_field_part1.py

@@ -0,0 +1,22 @@
+# Generated by Django 3.0.4 on 2020-04-20 14:59
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('testapp', '0005_test_issue45_unique_type_change_part2'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='TestRemoveOneToOneFieldModel',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('a', models.CharField(max_length=50)),
+                ('b', models.OneToOneField(null=True, on_delete=django.db.models.deletion.SET_NULL, to='testapp.TestRemoveOneToOneFieldModel')),
+            ],
+        ),
+    ]

testapp/migrations/0007_test_remove_onetoone_field_part2.py

@@ -0,0 +1,17 @@
+# Generated by Django 3.0.4 on 2020-04-20 14:59
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('testapp', '0006_test_remove_onetoone_field_part1'),
+    ]
+
+    operations = [
+        migrations.RemoveField(
+            model_name='testremoveonetoonefieldmodel',
+            name='b',
+        ),
+    ]

testapp/models.py

@@ -64,3 +64,10 @@ class Meta:
     a = models.CharField(max_length=51, null=True)
     b = models.CharField(max_length=50)
     c = models.CharField(max_length=50)
+
+
+class TestRemoveOneToOneFieldModel(models.Model):
+    # Fields used for testing removing OneToOne field. Verifies that delete_unique do not try to remove indexes
+    # thats already is removed.
+    # b = models.OneToOneField('self', on_delete=models.SET_NULL, null=True)
+    a = models.CharField(max_length=50)