import datetime import ujson import zlib from django.utils.translation import ugettext as _ from django.utils.timezone import now as timezone_now from django.db.models import Sum from analytics.lib.counts import COUNT_STATS, RealmCount from zerver.lib.avatar import get_avatar_field import zerver.lib.bugdown as bugdown from zerver.lib.cache import ( cache_with_key, generic_bulk_cached_fetch, to_dict_cache_key, to_dict_cache_key_id, realm_first_visible_message_id_cache_key, cache_get, cache_set, ) from zerver.lib.request import JsonableError from zerver.lib.stream_subscription import ( get_stream_subscriptions_for_user, ) from zerver.lib.timestamp import datetime_to_timestamp from zerver.lib.topic_mutes import ( build_topic_mute_checker, topic_is_muted, ) from zerver.models import ( get_display_recipient_by_id, get_user_profile_by_id, query_for_ids, Message, Realm, Recipient, Stream, SubMessage, Subscription, UserProfile, UserMessage, Reaction ) from typing import Any, Dict, List, Optional, Set, Tuple, Union from mypy_extensions import TypedDict RealmAlertWords = Dict[int, List[str]] RawUnreadMessagesResult = TypedDict('RawUnreadMessagesResult', { 'pm_dict': Dict[int, Any], 'stream_dict': Dict[int, Any], 'huddle_dict': Dict[int, Any], 'mentions': Set[int], 'muted_stream_ids': List[int], 'unmuted_stream_msgs': Set[int], }) UnreadMessagesResult = TypedDict('UnreadMessagesResult', { 'pms': List[Dict[str, Any]], 'streams': List[Dict[str, Any]], 'huddles': List[Dict[str, Any]], 'mentions': List[int], 'count': int, }) MAX_UNREAD_MESSAGES = 5000 def messages_for_ids(message_ids: List[int], user_message_flags: Dict[int, List[str]], search_fields: Dict[int, Dict[str, str]], apply_markdown: bool, client_gravatar: bool, allow_edit_history: bool) -> List[Dict[str, Any]]: cache_transformer = MessageDict.build_dict_from_raw_db_row id_fetcher = lambda row: row['id'] message_dicts = generic_bulk_cached_fetch(to_dict_cache_key_id, MessageDict.get_raw_db_rows, message_ids, id_fetcher=id_fetcher, cache_transformer=cache_transformer, extractor=extract_message_dict, setter=stringify_message_dict) message_list = [] # type: List[Dict[str, Any]] for message_id in message_ids: msg_dict = message_dicts[message_id] msg_dict.update({"flags": user_message_flags[message_id]}) if message_id in search_fields: msg_dict.update(search_fields[message_id]) # Make sure that we never send message edit history to clients # in realms with allow_edit_history disabled. if "edit_history" in msg_dict and not allow_edit_history: del msg_dict["edit_history"] message_list.append(msg_dict) MessageDict.post_process_dicts(message_list, apply_markdown, client_gravatar) return message_list def sew_messages_and_reactions(messages: List[Dict[str, Any]], reactions: List[Dict[str, Any]]) -> List[Dict[str, Any]]: """Given a iterable of messages and reactions stitch reactions into messages. """ # Add all messages with empty reaction item for message in messages: message['reactions'] = [] # Convert list of messages into dictionary to make reaction stitching easy converted_messages = {message['id']: message for message in messages} for reaction in reactions: converted_messages[reaction['message_id']]['reactions'].append( reaction) return list(converted_messages.values()) def sew_messages_and_submessages(messages: List[Dict[str, Any]], submessages: List[Dict[str, Any]]) -> None: # This is super similar to sew_messages_and_reactions. for message in messages: message['submessages'] = [] message_dict = {message['id']: message for message in messages} for submessage in submessages: message_id = submessage['message_id'] if message_id in message_dict: message = message_dict[message_id] message['submessages'].append(submessage) def extract_message_dict(message_bytes: bytes) -> Dict[str, Any]: return ujson.loads(zlib.decompress(message_bytes).decode("utf-8")) def stringify_message_dict(message_dict: Dict[str, Any]) -> bytes: return zlib.compress(ujson.dumps(message_dict).encode()) @cache_with_key(to_dict_cache_key, timeout=3600*24) def message_to_dict_json(message: Message) -> bytes: return MessageDict.to_dict_uncached(message) class MessageDict: @staticmethod def wide_dict(message: Message) -> Dict[str, Any]: ''' The next two lines get the cachable field related to our message object, with the side effect of populating the cache. ''' json = message_to_dict_json(message) obj = extract_message_dict(json) ''' The steps below are similar to what we do in post_process_dicts(), except we don't call finalize_payload(), since that step happens later in the queue processor. ''' MessageDict.bulk_hydrate_sender_info([obj]) MessageDict.hydrate_recipient_info(obj) return obj @staticmethod def post_process_dicts(objs: List[Dict[str, Any]], apply_markdown: bool, client_gravatar: bool) -> None: MessageDict.bulk_hydrate_sender_info(objs) for obj in objs: MessageDict.hydrate_recipient_info(obj) MessageDict.finalize_payload(obj, apply_markdown, client_gravatar) @staticmethod def finalize_payload(obj: Dict[str, Any], apply_markdown: bool, client_gravatar: bool) -> None: MessageDict.set_sender_avatar(obj, client_gravatar) if apply_markdown: obj['content_type'] = 'text/html' obj['content'] = obj['rendered_content'] else: obj['content_type'] = 'text/x-markdown' del obj['rendered_content'] del obj['sender_realm_id'] del obj['sender_avatar_source'] del obj['sender_avatar_version'] del obj['raw_display_recipient'] del obj['recipient_type'] del obj['recipient_type_id'] del obj['sender_is_mirror_dummy'] @staticmethod def to_dict_uncached(message: Message) -> bytes: dct = MessageDict.to_dict_uncached_helper(message) return stringify_message_dict(dct) @staticmethod def to_dict_uncached_helper(message: Message) -> Dict[str, Any]: return MessageDict.build_message_dict( message = message, message_id = message.id, last_edit_time = message.last_edit_time, edit_history = message.edit_history, content = message.content, subject = message.subject, pub_date = message.pub_date, rendered_content = message.rendered_content, rendered_content_version = message.rendered_content_version, sender_id = message.sender.id, sender_realm_id = message.sender.realm_id, sending_client_name = message.sending_client.name, recipient_id = message.recipient.id, recipient_type = message.recipient.type, recipient_type_id = message.recipient.type_id, reactions = Reaction.get_raw_db_rows([message.id]), submessages = SubMessage.get_raw_db_rows([message.id]), ) @staticmethod def get_raw_db_rows(needed_ids: List[int]) -> List[Dict[str, Any]]: # This is a special purpose function optimized for # callers like get_messages_backend(). fields = [ 'id', 'subject', 'pub_date', 'last_edit_time', 'edit_history', 'content', 'rendered_content', 'rendered_content_version', 'recipient_id', 'recipient__type', 'recipient__type_id', 'sender_id', 'sending_client__name', 'sender__realm_id', ] messages = Message.objects.filter(id__in=needed_ids).values(*fields) submessages = SubMessage.get_raw_db_rows(needed_ids) sew_messages_and_submessages(messages, submessages) reactions = Reaction.get_raw_db_rows(needed_ids) return sew_messages_and_reactions(messages, reactions) @staticmethod def build_dict_from_raw_db_row(row: Dict[str, Any]) -> Dict[str, Any]: ''' row is a row from a .values() call, and it needs to have all the relevant fields populated ''' return MessageDict.build_message_dict( message = None, message_id = row['id'], last_edit_time = row['last_edit_time'], edit_history = row['edit_history'], content = row['content'], subject = row['subject'], pub_date = row['pub_date'], rendered_content = row['rendered_content'], rendered_content_version = row['rendered_content_version'], sender_id = row['sender_id'], sender_realm_id = row['sender__realm_id'], sending_client_name = row['sending_client__name'], recipient_id = row['recipient_id'], recipient_type = row['recipient__type'], recipient_type_id = row['recipient__type_id'], reactions=row['reactions'], submessages=row['submessages'], ) @staticmethod def build_message_dict( message: Optional[Message], message_id: int, last_edit_time: Optional[datetime.datetime], edit_history: Optional[str], content: str, subject: str, pub_date: datetime.datetime, rendered_content: Optional[str], rendered_content_version: Optional[int], sender_id: int, sender_realm_id: int, sending_client_name: str, recipient_id: int, recipient_type: int, recipient_type_id: int, reactions: List[Dict[str, Any]], submessages: List[Dict[str, Any]] ) -> Dict[str, Any]: obj = dict( id = message_id, sender_id = sender_id, content = content, recipient_type_id = recipient_type_id, recipient_type = recipient_type, recipient_id = recipient_id, subject = subject, timestamp = datetime_to_timestamp(pub_date), client = sending_client_name) obj['sender_realm_id'] = sender_realm_id obj['raw_display_recipient'] = get_display_recipient_by_id( recipient_id, recipient_type, recipient_type_id ) obj['subject_links'] = bugdown.subject_links(sender_realm_id, subject) if last_edit_time is not None: obj['last_edit_timestamp'] = datetime_to_timestamp(last_edit_time) assert edit_history is not None obj['edit_history'] = ujson.loads(edit_history) if Message.need_to_render_content(rendered_content, rendered_content_version, bugdown.version): if message is None: # We really shouldn't be rendering objects in this method, but there is # a scenario where we upgrade the version of bugdown and fail to run # management commands to re-render historical messages, and then we # need to have side effects. This method is optimized to not need full # blown ORM objects, but the bugdown renderer is unfortunately highly # coupled to Message, and we also need to persist the new rendered content. # If we don't have a message object passed in, we get one here. The cost # of going to the DB here should be overshadowed by the cost of rendering # and updating the row. # TODO: see #1379 to eliminate bugdown dependencies message = Message.objects.select_related().get(id=message_id) assert message is not None # Hint for mypy. # It's unfortunate that we need to have side effects on the message # in some cases. rendered_content = render_markdown(message, content, realm=message.get_realm()) message.rendered_content = rendered_content message.rendered_content_version = bugdown.version message.save_rendered_content() if rendered_content is not None: obj['rendered_content'] = rendered_content else: obj['rendered_content'] = ('

[Zulip note: Sorry, we could not ' + 'understand the formatting of your message]

') if rendered_content is not None: obj['is_me_message'] = Message.is_status_message(content, rendered_content) else: obj['is_me_message'] = False obj['reactions'] = [ReactionDict.build_dict_from_raw_db_row(reaction) for reaction in reactions] obj['submessages'] = submessages return obj @staticmethod def bulk_hydrate_sender_info(objs: List[Dict[str, Any]]) -> None: sender_ids = list({ obj['sender_id'] for obj in objs }) if not sender_ids: return query = UserProfile.objects.values( 'id', 'full_name', 'short_name', 'email', 'realm__string_id', 'avatar_source', 'avatar_version', 'is_mirror_dummy', ) rows = query_for_ids(query, sender_ids, 'zerver_userprofile.id') sender_dict = { row['id']: row for row in rows } for obj in objs: sender_id = obj['sender_id'] user_row = sender_dict[sender_id] obj['sender_full_name'] = user_row['full_name'] obj['sender_short_name'] = user_row['short_name'] obj['sender_email'] = user_row['email'] obj['sender_realm_str'] = user_row['realm__string_id'] obj['sender_avatar_source'] = user_row['avatar_source'] obj['sender_avatar_version'] = user_row['avatar_version'] obj['sender_is_mirror_dummy'] = user_row['is_mirror_dummy'] @staticmethod def hydrate_recipient_info(obj: Dict[str, Any]) -> None: ''' This method hyrdrates recipient info with things like full names and emails of senders. Eventually our clients should be able to hyrdrate these fields themselves with info they already have on users. ''' display_recipient = obj['raw_display_recipient'] recipient_type = obj['recipient_type'] recipient_type_id = obj['recipient_type_id'] sender_is_mirror_dummy = obj['sender_is_mirror_dummy'] sender_email = obj['sender_email'] sender_full_name = obj['sender_full_name'] sender_short_name = obj['sender_short_name'] sender_id = obj['sender_id'] if recipient_type == Recipient.STREAM: display_type = "stream" elif recipient_type in (Recipient.HUDDLE, Recipient.PERSONAL): assert not isinstance(display_recipient, str) display_type = "private" if len(display_recipient) == 1: # add the sender in if this isn't a message between # someone and themself, preserving ordering recip = {'email': sender_email, 'full_name': sender_full_name, 'short_name': sender_short_name, 'id': sender_id, 'is_mirror_dummy': sender_is_mirror_dummy} if recip['email'] < display_recipient[0]['email']: display_recipient = [recip, display_recipient[0]] elif recip['email'] > display_recipient[0]['email']: display_recipient = [display_recipient[0], recip] else: raise AssertionError("Invalid recipient type %s" % (recipient_type,)) obj['display_recipient'] = display_recipient obj['type'] = display_type if obj['type'] == 'stream': obj['stream_id'] = recipient_type_id @staticmethod def set_sender_avatar(obj: Dict[str, Any], client_gravatar: bool) -> None: sender_id = obj['sender_id'] sender_realm_id = obj['sender_realm_id'] sender_email = obj['sender_email'] sender_avatar_source = obj['sender_avatar_source'] sender_avatar_version = obj['sender_avatar_version'] obj['avatar_url'] = get_avatar_field( user_id=sender_id, realm_id=sender_realm_id, email=sender_email, avatar_source=sender_avatar_source, avatar_version=sender_avatar_version, medium=False, client_gravatar=client_gravatar, ) class ReactionDict: @staticmethod def build_dict_from_raw_db_row(row: Dict[str, Any]) -> Dict[str, Any]: return {'emoji_name': row['emoji_name'], 'emoji_code': row['emoji_code'], 'reaction_type': row['reaction_type'], 'user': {'email': row['user_profile__email'], 'id': row['user_profile__id'], 'full_name': row['user_profile__full_name']}} def access_message(user_profile: UserProfile, message_id: int) -> Tuple[Message, UserMessage]: """You can access a message by ID in our APIs that either: (1) You received or have previously accessed via starring (aka have a UserMessage row for). (2) Was sent to a public stream in your realm. We produce consistent, boring error messages to avoid leaking any information from a security perspective. """ try: message = Message.objects.select_related().get(id=message_id) except Message.DoesNotExist: raise JsonableError(_("Invalid message(s)")) try: user_message = UserMessage.objects.select_related().get(user_profile=user_profile, message=message) except UserMessage.DoesNotExist: user_message = None if user_message is None: if message.recipient.type != Recipient.STREAM: # You can't access private messages you didn't receive raise JsonableError(_("Invalid message(s)")) stream = Stream.objects.get(id=message.recipient.type_id) if stream.realm != user_profile.realm: # You can't access public stream messages in other realms raise JsonableError(_("Invalid message(s)")) if not stream.is_public(): if not stream.is_history_public_to_subscribers(): # You can't access messages sent to invite-only streams # that you didn't receive raise JsonableError(_("Invalid message(s)")) # This stream is an invite-only stream where message # history is available to subscribers. So we check if # you're subscribed. if not Subscription.objects.filter(user_profile=user_profile, active=True, recipient=message.recipient).exists(): raise JsonableError(_("Invalid message(s)")) # You are subscribed, so let this fall through to the public stream case. else: # Otherwise, the message was sent to a public stream in # your realm, so return the message, user_message pair pass return (message, user_message) def render_markdown(message: Message, content: str, realm: Optional[Realm]=None, realm_alert_words: Optional[RealmAlertWords]=None, user_ids: Optional[Set[int]]=None, mention_data: Optional[bugdown.MentionData]=None, email_gateway: Optional[bool]=False) -> str: """Return HTML for given markdown. Bugdown may add properties to the message object such as `mentions_user_ids`, `mentions_user_group_ids`, and `mentions_wildcard`. These are only on this Django object and are not saved in the database. """ if user_ids is None: message_user_ids = set() # type: Set[int] else: message_user_ids = user_ids message.mentions_wildcard = False message.mentions_user_ids = set() message.mentions_user_group_ids = set() message.alert_words = set() message.links_for_preview = set() if realm is None: realm = message.get_realm() possible_words = set() # type: Set[str] if realm_alert_words is not None: for user_id, words in realm_alert_words.items(): if user_id in message_user_ids: possible_words.update(set(words)) sent_by_bot = get_user_profile_by_id(message.sender_id).is_bot # DO MAIN WORK HERE -- call bugdown to convert rendered_content = bugdown.convert( content, message=message, message_realm=realm, possible_words=possible_words, sent_by_bot=sent_by_bot, mention_data=mention_data, email_gateway=email_gateway ) if message is not None: message.user_ids_with_alert_words = set() if realm_alert_words is not None: for user_id, words in realm_alert_words.items(): if user_id in message_user_ids: if set(words).intersection(message.alert_words): message.user_ids_with_alert_words.add(user_id) return rendered_content def huddle_users(recipient_id: int) -> str: display_recipient = get_display_recipient_by_id(recipient_id, Recipient.HUDDLE, None) # type: Union[str, List[Dict[str, Any]]] # str is for streams. assert not isinstance(display_recipient, str) user_ids = [obj['id'] for obj in display_recipient] # type: List[int] user_ids = sorted(user_ids) return ','.join(str(uid) for uid in user_ids) def aggregate_message_dict(input_dict: Dict[int, Dict[str, Any]], lookup_fields: List[str], collect_senders: bool) -> List[Dict[str, Any]]: lookup_dict = dict() # type: Dict[Tuple[Any, ...], Dict[str, Any]] ''' A concrete example might help explain the inputs here: input_dict = { 1002: dict(stream_id=5, topic='foo', sender_id=40), 1003: dict(stream_id=5, topic='foo', sender_id=41), 1004: dict(stream_id=6, topic='baz', sender_id=99), } lookup_fields = ['stream_id', 'topic'] The first time through the loop: attribute_dict = dict(stream_id=5, topic='foo', sender_id=40) lookup_dict = (5, 'foo') lookup_dict = { (5, 'foo'): dict(stream_id=5, topic='foo', unread_message_ids=[1002, 1003], sender_ids=[40, 41], ), ... } result = [ dict(stream_id=5, topic='foo', unread_message_ids=[1002, 1003], sender_ids=[40, 41], ), ... ] ''' for message_id, attribute_dict in input_dict.items(): lookup_key = tuple([attribute_dict[f] for f in lookup_fields]) if lookup_key not in lookup_dict: obj = {} for f in lookup_fields: obj[f] = attribute_dict[f] obj['unread_message_ids'] = [] if collect_senders: obj['sender_ids'] = set() lookup_dict[lookup_key] = obj bucket = lookup_dict[lookup_key] bucket['unread_message_ids'].append(message_id) if collect_senders: bucket['sender_ids'].add(attribute_dict['sender_id']) for dct in lookup_dict.values(): dct['unread_message_ids'].sort() if collect_senders: dct['sender_ids'] = sorted(list(dct['sender_ids'])) sorted_keys = sorted(lookup_dict.keys()) return [lookup_dict[k] for k in sorted_keys] def get_inactive_recipient_ids(user_profile: UserProfile) -> List[int]: rows = get_stream_subscriptions_for_user(user_profile).filter( active=False, ).values( 'recipient_id' ) inactive_recipient_ids = [ row['recipient_id'] for row in rows] return inactive_recipient_ids def get_muted_stream_ids(user_profile: UserProfile) -> List[int]: rows = get_stream_subscriptions_for_user(user_profile).filter( active=True, in_home_view=False, ).values( 'recipient__type_id' ) muted_stream_ids = [ row['recipient__type_id'] for row in rows] return muted_stream_ids def get_raw_unread_data(user_profile: UserProfile) -> RawUnreadMessagesResult: excluded_recipient_ids = get_inactive_recipient_ids(user_profile) user_msgs = UserMessage.objects.filter( user_profile=user_profile ).exclude( message__recipient_id__in=excluded_recipient_ids ).extra( where=[UserMessage.where_unread()] ).values( 'message_id', 'message__sender_id', 'message__subject', 'message__recipient_id', 'message__recipient__type', 'message__recipient__type_id', 'flags', ).order_by("-message_id") # Limit unread messages for performance reasons. user_msgs = list(user_msgs[:MAX_UNREAD_MESSAGES]) rows = list(reversed(user_msgs)) muted_stream_ids = get_muted_stream_ids(user_profile) topic_mute_checker = build_topic_mute_checker(user_profile) def is_row_muted(stream_id: int, recipient_id: int, topic: str) -> bool: if stream_id in muted_stream_ids: return True if topic_mute_checker(recipient_id, topic): return True return False huddle_cache = {} # type: Dict[int, str] def get_huddle_users(recipient_id: int) -> str: if recipient_id in huddle_cache: return huddle_cache[recipient_id] user_ids_string = huddle_users(recipient_id) huddle_cache[recipient_id] = user_ids_string return user_ids_string pm_dict = {} stream_dict = {} unmuted_stream_msgs = set() huddle_dict = {} mentions = set() for row in rows: message_id = row['message_id'] msg_type = row['message__recipient__type'] recipient_id = row['message__recipient_id'] sender_id = row['message__sender_id'] if msg_type == Recipient.STREAM: stream_id = row['message__recipient__type_id'] topic = row['message__subject'] stream_dict[message_id] = dict( stream_id=stream_id, topic=topic, sender_id=sender_id, ) if not is_row_muted(stream_id, recipient_id, topic): unmuted_stream_msgs.add(message_id) elif msg_type == Recipient.PERSONAL: pm_dict[message_id] = dict( sender_id=sender_id, ) elif msg_type == Recipient.HUDDLE: user_ids_string = get_huddle_users(recipient_id) huddle_dict[message_id] = dict( user_ids_string=user_ids_string, ) is_mentioned = (row['flags'] & UserMessage.flags.mentioned) != 0 if is_mentioned: mentions.add(message_id) return dict( pm_dict=pm_dict, stream_dict=stream_dict, muted_stream_ids=muted_stream_ids, unmuted_stream_msgs=unmuted_stream_msgs, huddle_dict=huddle_dict, mentions=mentions, ) def aggregate_unread_data(raw_data: RawUnreadMessagesResult) -> UnreadMessagesResult: pm_dict = raw_data['pm_dict'] stream_dict = raw_data['stream_dict'] unmuted_stream_msgs = raw_data['unmuted_stream_msgs'] huddle_dict = raw_data['huddle_dict'] mentions = list(raw_data['mentions']) count = len(pm_dict) + len(unmuted_stream_msgs) + len(huddle_dict) pm_objects = aggregate_message_dict( input_dict=pm_dict, lookup_fields=[ 'sender_id', ], collect_senders=False, ) stream_objects = aggregate_message_dict( input_dict=stream_dict, lookup_fields=[ 'stream_id', 'topic', ], collect_senders=True, ) huddle_objects = aggregate_message_dict( input_dict=huddle_dict, lookup_fields=[ 'user_ids_string', ], collect_senders=False, ) result = dict( pms=pm_objects, streams=stream_objects, huddles=huddle_objects, mentions=mentions, count=count) # type: UnreadMessagesResult return result def apply_unread_message_event(user_profile: UserProfile, state: Dict[str, Any], message: Dict[str, Any], flags: List[str]) -> None: message_id = message['id'] if message['type'] == 'stream': message_type = 'stream' elif message['type'] == 'private': others = [ recip for recip in message['display_recipient'] if recip['id'] != message['sender_id'] ] if len(others) <= 1: message_type = 'private' else: message_type = 'huddle' else: raise AssertionError("Invalid message type %s" % (message['type'],)) sender_id = message['sender_id'] if message_type == 'stream': stream_id = message['stream_id'] topic = message['subject'] new_row = dict( stream_id=stream_id, topic=topic, sender_id=sender_id, ) state['stream_dict'][message_id] = new_row if stream_id not in state['muted_stream_ids']: # This next check hits the database. if not topic_is_muted(user_profile, stream_id, topic): state['unmuted_stream_msgs'].add(message_id) elif message_type == 'private': sender_id = message['sender_id'] new_row = dict( sender_id=sender_id, ) state['pm_dict'][message_id] = new_row else: display_recipient = message['display_recipient'] user_ids = [obj['id'] for obj in display_recipient] user_ids = sorted(user_ids) user_ids_string = ','.join(str(uid) for uid in user_ids) new_row = dict( user_ids_string=user_ids_string, ) state['huddle_dict'][message_id] = new_row if 'mentioned' in flags: state['mentions'].add(message_id) def estimate_recent_messages(realm: Realm, hours: int) -> int: stat = COUNT_STATS['messages_sent:is_bot:hour'] d = timezone_now() - datetime.timedelta(hours=hours) return RealmCount.objects.filter(property=stat.property, end_time__gt=d, realm=realm).aggregate(Sum('value'))['value__sum'] or 0 def get_first_visible_message_id(realm: Realm) -> int: val = cache_get(realm_first_visible_message_id_cache_key(realm)) if val is not None: return val[0] return 0 def maybe_update_first_visible_message_id(realm: Realm, lookback_hours: int) -> None: cache_empty = cache_get(realm_first_visible_message_id_cache_key(realm)) is None recent_messages_count = estimate_recent_messages(realm, lookback_hours) if realm.message_visibility_limit is not None and (recent_messages_count > 0 or cache_empty): update_first_visible_message_id(realm) def update_first_visible_message_id(realm: Realm) -> None: try: # We have verified that the limit is not none before calling this function. assert realm.message_visibility_limit is not None first_visible_message_id = Message.objects.filter(sender__realm=realm).values('id').\ order_by('-id')[realm.message_visibility_limit - 1]["id"] except IndexError: first_visible_message_id = 0 cache_set(realm_first_visible_message_id_cache_key(realm), first_visible_message_id)