Filtering logic for state events (used to speed up ACL federation checks) seems broken?

[ara4n]

storage/state.py's _get_state_for_groups claims that if you pass in a types list with an entry with a state_key of None, the None will match all state_keys of the given type:

synapse/synapse/storage/state.py

Lines 505 to 509 in 106906a

	def _get_state_for_groups(self, groups, types=None):
	"""Given list of groups returns dict of group -> list of state events
	with matching types. `types` is a list of `(type, state_key)`, where
	a `state_key` of None matches all state_keys. If `types` is None then
	all events are returned.

This looks to be correct when we're querying the cache, thanks to:

synapse/synapse/storage/state.py

Lines 461 to 462 in 106906a

	if state_key is None:
	type_to_key[typ] = None

However, it doesn't look like it's correct when we're querying the DB - where the None looks like it's turned into an AND state_key = NULL or similar?

synapse/synapse/storage/state.py

Lines 239 to 244 in 106906a

	clause_to_args = [
	(
	"AND type = ? AND state_key = ?",
	(etype, state_key)
	)
	for etype, state_key in types

[ara4n]

from #synapse-dev: "this looks to be a real bug"

[ara4n]

fixed by #2990