wrap beatmap deletion in transactions

map and score deletions were separate operations with no transaction
wrapping. if the process crashed between deleting maps and deleting
their scores, you'd end up with orphaned score rows pointing at maps
that no longer exist.

both deletion paths (map update and full set removal) now use
transactions.

Author: raya-ac

app/objects/beatmap.py

@@ -728,17 +728,18 @@ async def _update_if_available(self) -> None:
             # save changes to sql
 
             if map_md5s_to_delete:
-                # delete maps
-                await app.state.services.database.execute(
-                    "DELETE FROM maps WHERE md5 IN :map_md5s",
-                    {"map_md5s": map_md5s_to_delete},
-                )
+                async with app.state.services.database.transaction():
+                    # delete maps
+                    await app.state.services.database.execute(
+                        "DELETE FROM maps WHERE md5 IN :map_md5s",
+                        {"map_md5s": map_md5s_to_delete},
+                    )
 
-                # delete scores on the maps
-                await app.state.services.database.execute(
-                    "DELETE FROM scores WHERE map_md5 IN :map_md5s",
-                    {"map_md5s": map_md5s_to_delete},
-                )
+                    # delete scores on the maps
+                    await app.state.services.database.execute(
+                        "DELETE FROM scores WHERE map_md5 IN :map_md5s",
+                        {"map_md5s": map_md5s_to_delete},
+                    )
 
             # update last_osuapi_check
             await app.state.services.database.execute(
@@ -761,27 +762,28 @@ async def _update_if_available(self) -> None:
             # TODO: a couple of open questions here:
             # - should we delete the beatmap from the database if it's not in the osu!api?
             # - are 404 and 200 the only cases where we should delete the beatmap?
-            if self.maps:
-                map_md5s_to_delete = {bmap.md5 for bmap in self.maps}
+            async with app.state.services.database.transaction():
+                if self.maps:
+                    map_md5s_to_delete = {bmap.md5 for bmap in self.maps}
+
+                    # delete maps
+                    await app.state.services.database.execute(
+                        "DELETE FROM maps WHERE md5 IN :map_md5s",
+                        {"map_md5s": map_md5s_to_delete},
+                    )
 
-                # delete maps
-                await app.state.services.database.execute(
-                    "DELETE FROM maps WHERE md5 IN :map_md5s",
-                    {"map_md5s": map_md5s_to_delete},
-                )
+                    # delete scores on the maps
+                    await app.state.services.database.execute(
+                        "DELETE FROM scores WHERE map_md5 IN :map_md5s",
+                        {"map_md5s": map_md5s_to_delete},
+                    )
 
-                # delete scores on the maps
+                # delete set
                 await app.state.services.database.execute(
-                    "DELETE FROM scores WHERE map_md5 IN :map_md5s",
-                    {"map_md5s": map_md5s_to_delete},
+                    "DELETE FROM mapsets WHERE id = :set_id",
+                    {"set_id": self.id},
                 )
 
-            # delete set
-            await app.state.services.database.execute(
-                "DELETE FROM mapsets WHERE id = :set_id",
-                {"set_id": self.id},
-            )
-
     async def _save_to_sql(self) -> None:
         """Save the object's attributes into the database."""
         await app.state.services.database.execute_many(