add creation timestamp to movies

unwind/models.py

@@ -35,6 +35,9 @@ def fields(class_or_instance):
 
     for f in _fields(class_or_instance):
 
+        if f.name == "_is_lazy":
+            continue
+
         if (attn := annotations(f.type)) and _RelationSentinel in attn:
             continue  # Relations are ignored
 
@@ -167,8 +170,36 @@ class Movie:
     imdb_votes: Optional[int] = None
     runtime: Optional[int] = None  # minutes
     genres: set[str] = None
+    created: datetime = field(default_factory=utcnow)
     updated: datetime = field(default_factory=utcnow)
 
+    _is_lazy: bool = field(default=False, init=False, repr=False, compare=False)
+
+    @classmethod
+    def lazy(cls, **kwds):
+        """Return a new instance without running default factories.
+
+        This is meant purely for optimization purposes, to postpone possibly
+        expensive initialization operations.
+        """
+        # XXX optimize using a metaclass & storing field refs on the class
+        kwds.setdefault("id", None)
+        kwds.setdefault("created", None)
+        kwds.setdefault("updated", None)
+        movie = cls(**kwds)
+        movie._is_lazy = True
+        return movie
+
+    def _lazy_init(self):
+        if not self._is_lazy:
+            return
+
+        for field in fields(Movie):
+            if getattr(self, field.name) is None and field.default_factory:
+                setattr(self, field.name, field.default_factory())
+
+        self._is_lazy = False
+
 
 T = TypeVar("T")
 _RelationSentinel = object()