tidy(migrator): remove logic to check if graph_executions exists in migration 5

Initially I wanted to show how many sessions were being deleted. In hindsight, this is not great:
- It requires extra logic in the migrator, which should be as simple as possible.
- It may be alarming to see "Clearing 224591 old sessions".

The app still reports on freed space during the DB startup logic.

invokeai/app/services/shared/sqlite/sqlite_util.py

@@ -32,7 +32,7 @@ def init_db(config: InvokeAIAppConfig, logger: Logger, image_files: ImageFileSto
     migrator.register_migration(build_migration_2(image_files=image_files, logger=logger))
     migrator.register_migration(build_migration_3(app_config=config, logger=logger))
     migrator.register_migration(build_migration_4())
-    migrator.register_migration(build_migration_5(logger=logger))
+    migrator.register_migration(build_migration_5())
     migrator.run_migrations()
 
     return db

invokeai/app/services/shared/sqlite_migrator/migrations/migration_5.py

@@ -1,59 +1,23 @@
 import sqlite3
-from logging import Logger
-from typing import cast
 
 from invokeai.app.services.shared.sqlite_migrator.sqlite_migrator_common import Migration
 
 
 class Migration5Callback:
-    def __init__(self, logger: Logger):
-        self._logger = logger
-
     def __call__(self, cursor: sqlite3.Cursor) -> None:
         self._drop_graph_executions(cursor)
 
     def _drop_graph_executions(self, cursor: sqlite3.Cursor) -> None:
         """Drops the `graph_executions` table."""
 
-        # Check if the table exists first. This shouldn't ever be an issue for users, but it is for tests.
-        #
-        # Unlike other database tables, whose schemas are managed by the migrator, `graph_executions`
-        # is created and managed by an instance of `SqliteItemStorage``. Specifically, it is created in the
-        # `__init__` of `SqliteItemStorage`.
-        #
-        # In tests, we don't always create an instance of `SqliteItemStorage`, so the table may not exist in
-        # the test memory db fixture.
-        #
-        # We _do_, however, run the migrator on the test memory db fixtures. So, we need to check if the
-        # table exists before dropping it, else unrelated tests will fail.
-        #
-        # This song and dance won't be necessary again, because we aren't using `SqliteItemStorage` for anything
-        # moving forward.
-
         cursor.execute(
             """--sql
-            SELECT name FROM sqlite_master WHERE type='table' AND name='graph_executions';
+            DROP TABLE IF EXISTS graph_executions;
             """
         )
 
-        if cursor.fetchone():
-            cursor.execute(
-                """--sql
-                SELECT COUNT(*) FROM graph_executions;
-                """
-            )
-            count = cast(int, cursor.fetchone()[0])
-            self._logger.info(f"Clearing {count} old sessions from database")
-            cursor.execute(
-                """--sql
-                DROP TABLE IF EXISTS graph_executions;
-                """
-            )
-        else:
-            self._logger.info("No 'graph_executions' table found.")
 
-
-def build_migration_5(logger: Logger) -> Migration:
+def build_migration_5() -> Migration:
     """
     Build the migration from database version 4 to 5.
 
@@ -64,7 +28,7 @@ def build_migration_5(logger: Logger) -> Migration:
     migration_5 = Migration(
         from_version=4,
         to_version=5,
-        callback=Migration5Callback(logger=logger),
+        callback=Migration5Callback(),
     )
 
     return migration_5