Add deconstruct method

Author: WaVEV

django_mongodb_backend/indexes.py

@@ -212,6 +212,11 @@ def _check_similarity_functions(self, similarities):
                     f"'are {','.join(self.ALLOWED_SIMILARITY_FUNCTIONS)}"
                 )
 
+    def deconstruct(self):
+        path, args, kwargs = super().deconstruct()
+        kwargs["similarities"] = self.similarities
+        return path, args, kwargs
+
     def get_pymongo_index_model(
         self, model, schema_editor, field=None, unique=False, column_prefix=""
     ):

tests/indexes_/test_atlas_indexes.py

@@ -112,6 +112,25 @@ def assertAddRemoveIndex(self, editor, model, index):
             ),
         )
 
+    def test_deconstruct_default_similarity(self):
+        index = VectorSearchIndex(
+            name="recent_article_idx",
+            fields=["number"],
+        )
+        name, args, kwargs = index.deconstruct()
+        new = VectorSearchIndex(*args, **kwargs)
+        self.assertEqual(new.similarities, index.similarities)
+
+    def test_deconstruct_with_similarities(self):
+        index = VectorSearchIndex(
+            name="recent_article_idx",
+            fields=["number", "number"],
+            similarities=["cosine", "dotProduct"],
+        )
+        path, args, kwargs = index.deconstruct()
+        new = VectorSearchIndex(*args, **kwargs)
+        self.assertEqual(new.similarities, index.similarities)
+
     def test_simple_vector_search(self):
         with connection.schema_editor() as editor:
             index = VectorSearchIndex(