Improved code

Author: ankane

pgvector/django/functions.py

@@ -8,12 +8,10 @@ class DistanceBase(Func):
 
     def __init__(self, expression: Any, vector: Any, **extra: Any) -> None:
         if not hasattr(vector, 'resolve_expression'):
-            if isinstance(vector, HalfVector):
-                vector = Value(HalfVector._to_db(vector))
-            elif isinstance(vector, SparseVector):
-                vector = Value(SparseVector._to_db(vector))
-            else:
-                vector = Value(Vector._to_db(vector))
+            if isinstance(vector, (Vector, HalfVector, SparseVector)):
+                vector = Value(vector.to_text())
+            elif vector is not None:
+                vector = Value(Vector(vector).to_text())
 
             # prevent error with unhashable types
             self._constructor_args = ((expression, vector), extra)