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performance: Introduce new_stream_user_ids. 

Let
    U = number of users to subscribe
    S = number of streams to subscribe

We were technically doing N^3 amount of work
when we sent certain events, or to be more
precise, U * S * S amount of work.  For each
stream, we were looping through a list of tuples
of size U * S to find the users for the stream.

In practice either U or S is usually 1, so the
performance gains here are probably negligible,
especially since the constant factors here
were just slinging around Python data.

But the code is actually more readable now, so
it's a double win.
This commit is contained in:
Steve Howell 2020-10-13 15:29:21 +00:00 committed by Tim Abbott
parent ebb605319b
commit 18771099e4
1 changed files with 13 additions and 17 deletions
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30
zerver/lib/actions.py
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@ -2889,9 +2889,9 @@ def bulk_add_subscriptions(
# the following code and we want to minize DB queries
all_subscribers_by_stream = get_user_ids_for_streams(streams=streams)
new_streams: Set[Tuple[int, int]] = set()
new_stream_user_ids: Dict[int, Set[int]] = defaultdict(set)
for (sub, stream) in subs_to_add + subs_to_activate:
new_streams.add((sub.user_profile.id, stream.id))
new_stream_user_ids[stream.id].add(sub.user_profile_id)
# We now send several types of events to notify browsers. The
# first batch is notifications to users on invite-only streams
@ -2899,8 +2899,7 @@ def bulk_add_subscriptions(
send_stream_creation_events_for_private_streams(
realm=realm,
streams=streams,
new_streams=new_streams,
users=users,
new_stream_user_ids=new_stream_user_ids,
)
send_subscription_add_events(
@ -2911,8 +2910,7 @@ def bulk_add_subscriptions(
send_peer_add_events(
realm=realm,
users=users,
new_streams=new_streams,
new_stream_user_ids=new_stream_user_ids,
streams=streams,
all_subscribers_by_stream=all_subscribers_by_stream,
)
@ -2969,8 +2967,7 @@ def bulk_add_subs_to_db_with_logging(
def send_stream_creation_events_for_private_streams(
realm: Realm,
streams: Iterable[Stream],
new_streams: Set[Tuple[int, int]],
users: List[UserProfile],
new_stream_user_ids: Dict[int, Set[int]],
) -> None:
for stream in streams:
if not stream.is_public():
@ -2980,16 +2977,15 @@ def send_stream_creation_events_for_private_streams(
# they get the "subscribe" notification, and the latter so
# they can manage the new stream.
# Realm admins already have all created private streams.
realm_admin_ids = [user.id for user in realm.get_admin_users_and_bots()]
new_users_ids = [user.id for user in users if (user.id, stream.id) in new_streams and
user.id not in realm_admin_ids]
send_stream_creation_event(stream, new_users_ids)
stream_users_ids = new_stream_user_ids[stream.id]
realm_admin_ids = {user.id for user in realm.get_admin_users_and_bots()}
notify_user_ids = list(stream_users_ids - realm_admin_ids)
send_stream_creation_event(stream, notify_user_ids)
def send_peer_add_events(
realm: Realm,
users: List[UserProfile],
streams: Iterable[Stream],
new_streams: Set[Tuple[int, int]],
new_stream_user_ids: Dict[int, Set[int]],
all_subscribers_by_stream: Dict[int, List[int]],
) -> None:
# The second batch is events for other users who are tracking the
@ -2999,17 +2995,17 @@ def send_peer_add_events(
if stream.is_in_zephyr_realm and not stream.invite_only:
continue
new_user_ids = [user.id for user in users if (user.id, stream.id) in new_streams]
altered_user_ids = new_stream_user_ids[stream.id]
subscribed_user_ids = all_subscribers_by_stream[stream.id]
peer_user_ids = get_peer_user_ids_for_stream_change(
stream=stream,
altered_user_ids=new_user_ids,
altered_user_ids=altered_user_ids,
subscribed_user_ids=subscribed_user_ids,
)
if peer_user_ids:
for new_user_id in new_user_ids:
for new_user_id in altered_user_ids:
event = dict(type="subscription", op="peer_add",
stream_id=stream.id,
user_id=new_user_id)