add creation timestamp to movies

unwind/db.py

@@ -165,12 +165,9 @@ def shared_connection() -> Database:
 
 
 async def add(item):
-    # Support late initializing of `id` (used for optimization).
+    # Support late initializing - used for optimization.
-    if hasattr(item, "id") and getattr(item, "id") is None:
+    if getattr(item, "_is_lazy", False):
-        for f in fields(item):
+        item._lazy_init()
-            if f.name == "id":
-                item.id = f.default_factory()
-                break
 
     values = asplain(item)
     keys = ", ".join(f"{k}" for k in values)

unwind/imdb_import.py

@@ -50,7 +50,7 @@ class BasicRow:
 
     def as_movie(self):
         assert self.startYear is not None
-        return Movie(
+        return Movie.lazy(
             title=self.primaryTitle,
             original_title=self.originalTitle,
             release_year=self.startYear,
@@ -59,8 +59,6 @@ class BasicRow:
             imdb_score=None,
             runtime=self.runtimeMinutes,
             genres=self.genres or set(),
-            updated=None,  # optimization: skip default factory
-            id=None,  # optimization: skip default factory
         )
 
 
@@ -77,12 +75,10 @@ class RatingRow:
         return inst
 
     def as_movie(self):
-        return Movie(
+        return Movie.lazy(
             imdb_id=self.tconst,
             imdb_score=score_from_imdb_rating(self.averageRating),
             imdb_votes=self.numVotes,
-            updated=None,  # optimization: skip default factory
-            id=None,  # optimization: skip default factory
         )
 
 

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()

unwind/sql/20210721-213417.sql

@@ -0,0 +1,38 @@
+-- add creation timestamp to movies
+
+CREATE TABLE _migrate_movies (
+    id TEXT PRIMARY KEY NOT NULL,
+    title TEXT NOT NULL,
+    original_title TEXT,
+    release_year INTEGER NOT NULL,
+    media_type TEXT NOT NULL,
+    imdb_id TEXT NOT NULL UNIQUE,
+    imdb_score INTEGER,
+    imdb_votes INTEGER,
+    runtime INTEGER,
+    genres TEXT NOT NULL,
+    created TEXT NOT NULL,
+    updated TEXT NOT NULL
+);;
+
+INSERT INTO _migrate_movies
+SELECT
+    id,
+    title,
+    original_title,
+    release_year,
+    media_type,
+    imdb_id,
+    imdb_score,
+    imdb_votes,
+    runtime,
+    genres,
+    updated AS created,
+    updated
+FROM movies
+WHERE true;;
+
+DROP TABLE movies;;
+
+ALTER TABLE _migrate_movies
+RENAME TO movies;;