Ability to tell if a Database is an in-memory one

[simonw]

Currently the constructor accepts memory=True or memory_name=... and uses those to create a connection, but does not record what those values were:

sqlite-utils/sqlite_utils/db.py

Lines 307 to 349 in 1260bdc

	def __init__(
	self,
	filename_or_conn: Optional[Union[str, pathlib.Path, sqlite3.Connection]] = None,
	memory: bool = False,
	memory_name: Optional[str] = None,
	recreate: bool = False,
	recursive_triggers: bool = True,
	tracer: Optional[Callable] = None,
	use_counts_table: bool = False,
	execute_plugins: bool = True,
	):
	assert (filename_or_conn is not None and (not memory and not memory_name)) or (
	filename_or_conn is None and (memory or memory_name)
	), "Either specify a filename_or_conn or pass memory=True"
	if memory_name:
	uri = "file:{}?mode=memory&cache=shared".format(memory_name)
	self.conn = sqlite3.connect(
	uri,
	uri=True,
	check_same_thread=False,
	)
	elif memory or filename_or_conn == ":memory:":
	self.conn = sqlite3.connect(":memory:")
	elif isinstance(filename_or_conn, (str, pathlib.Path)):
	if recreate and os.path.exists(filename_or_conn):
	try:
	os.remove(filename_or_conn)
	except OSError:
	# Avoid mypy and __repr__ errors, see:
	# https://github.com/simonw/sqlite-utils/issues/503
	self.conn = sqlite3.connect(":memory:")
	raise
	self.conn = sqlite3.connect(str(filename_or_conn))
	else:
	assert not recreate, "recreate cannot be used with connections, only paths"
	self.conn = filename_or_conn
	self._tracer = tracer
	if recursive_triggers:
	self.execute("PRAGMA recursive_triggers=on;")
	self._registered_functions: set = set()
	self.use_counts_table = use_counts_table
	if execute_plugins:
	pm.hook.prepare_connection(conn=self.conn)

This makes it hard to tell if a database object is to an in-memory or a file-based database, which is sometimes useful to know.

[simonw]

Maybe just populate db.memory: bool and db.memory_name: Optional[str] for this, then document them.