Temp tables get removed after db migration

backend/db.py

@@ -1,8 +1,8 @@
 #-*- coding: utf-8 -*-
 
 from datetime import datetime
-from sqlite3 import Connection, Row
-from threading import current_thread
+from sqlite3 import Connection, ProgrammingError, Row
+from threading import current_thread, main_thread
 from time import time
 from typing import Union
 
@@ -14,7 +14,8 @@ class Singleton(type):
 	_instances = {}
 	def __call__(cls, *args, **kwargs):
 		i = f'{cls}{current_thread()}'
-		if i not in cls._instances:
+		if (i not in cls._instances
+      	or cls._instances[i].closed):
 			cls._instances[i] = super(Singleton, cls).__call__(*args, **kwargs)
 
 		return cls._instances[i]
@@ -25,6 +26,12 @@ class DBConnection(Connection, metaclass=Singleton):
 	def __init__(self, timeout: float) -> None:
 		super().__init__(self.file, timeout=timeout)
 		super().cursor().execute("PRAGMA foreign_keys = ON;")
+		self.closed = False
+		return
+
+	def close(self) -> None:
+		self.closed = True
+		super().close()
 		return
 
 def get_db(output_type: Union[dict, tuple]=tuple):
@@ -54,11 +61,13 @@ def close_db(e=None) -> None:
 	"""	
 	try:
 		cursor = g.cursor
-		db = cursor.connection
+		db: DBConnection = cursor.connection
 		cursor.close()
 		delattr(g, 'cursor')
 		db.commit()
-	except AttributeError:
+		if current_thread() is main_thread():
+			db.close()
+	except (AttributeError, ProgrammingError):
 		pass
 	return