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PERF: Optimize query for finding users with unread chat messages (#29964)

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Using CTEs and DISTINCT ON to:
- Pre-filter active users with correct preferences
- Get only first unread message per channel
- Eliminate redundant joins and message scanning

This reduces the query execution time by limiting message scanning and joins to only relevant users and messages.

Internal ref t/142836 & t/139517
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Régis Hanol 2024-11-28 15:28:37 +01:00 committed by GitHub
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1 changed files with 33 additions and 28 deletions
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61
plugins/chat/lib/chat/mailer.rb
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@ -30,38 +30,43 @@ module Chat
if Chat.allowed_group_ids.include?(Group::AUTO_GROUPS[:everyone])
""
else
"JOIN group_users ON group_users.user_id = users.id AND group_users.group_id IN (#{Chat.allowed_group_ids.join(",")})"
"JOIN group_users gu ON gu.user_id = u.id AND gu.group_id IN (#{Chat.allowed_group_ids.join(",")})"
end
DB.query_single <<~SQL
SELECT uccm.user_id
FROM user_chat_channel_memberships uccm
JOIN users ON users.id = uccm.user_id
JOIN user_options ON user_options.user_id = users.id
#{groups_join_sql}
JOIN chat_channels ON chat_channels.id = uccm.chat_channel_id
JOIN chat_messages ON chat_messages.chat_channel_id = chat_channels.id
JOIN users sender ON sender.id = chat_messages.user_id
LEFT JOIN chat_mentions ON chat_mentions.chat_message_id = chat_messages.id
LEFT JOIN chat_mention_notifications cmn ON cmn.chat_mention_id = chat_mentions.id
LEFT JOIN notifications ON notifications.id = cmn.notification_id AND notifications.user_id = uccm.user_id
WHERE NOT uccm.muted
AND (uccm.last_read_message_id IS NULL OR uccm.last_read_message_id < chat_messages.id)
AND (uccm.last_unread_mention_when_emailed_id IS NULL OR uccm.last_unread_mention_when_emailed_id < chat_messages.id)
AND users.last_seen_at < now() - interval '15 minutes'
AND user_options.chat_enabled
AND user_options.chat_email_frequency = #{UserOption.chat_email_frequencies[:when_away]}
AND user_options.email_level <> #{UserOption.email_level_types[:never]}
AND chat_channels.deleted_at IS NULL
AND chat_messages.deleted_at IS NULL
AND chat_messages.created_at > now() - interval '1 week'
AND chat_messages.user_id <> users.id
AND chat_messages.created_by_sdk = false
AND (
(chat_channels.chatable_type = 'DirectMessage' AND user_options.allow_private_messages) OR
(chat_channels.chatable_type = 'Category' AND uccm.following AND NOT notifications.read)
WITH eligible_users AS (
SELECT DISTINCT u.id, uo.allow_private_messages
FROM users u
JOIN user_options uo ON uo.user_id = u.id
#{groups_join_sql}
WHERE u.last_seen_at < now() - interval '15 minutes'
AND uo.chat_enabled
AND uo.chat_email_frequency = #{UserOption.chat_email_frequencies[:when_away]}
AND uo.email_level <> #{UserOption.email_level_types[:never]}
), channel_messages AS (
SELECT DISTINCT ON (chat_channel_id) chat_channel_id, cm.id AS first_unread_id, user_id AS sender_id
FROM chat_messages cm
JOIN users sender ON sender.id = cm.user_id
WHERE cm.created_at > now() - interval '7 days'
AND cm.deleted_at IS NULL
AND NOT cm.created_by_sdk
ORDER BY chat_channel_id, cm.id
)
SELECT DISTINCT uccm.user_id
FROM user_chat_channel_memberships uccm
JOIN chat_channels cc ON cc.id = uccm.chat_channel_id AND cc.deleted_at IS NULL
JOIN channel_messages cm ON cm.chat_channel_id = cc.id AND cm.sender_id <> uccm.user_id
JOIN eligible_users eu ON eu.id = uccm.user_id
LEFT JOIN chat_mentions mn ON mn.chat_message_id = cm.first_unread_id
LEFT JOIN chat_mention_notifications cmn ON cmn.chat_mention_id = mn.id
LEFT JOIN notifications n ON n.id = cmn.notification_id AND n.user_id = uccm.user_id
WHERE NOT uccm.muted
AND (uccm.last_read_message_id IS NULL OR cm.first_unread_id > uccm.last_read_message_id)
AND (uccm.last_unread_mention_when_emailed_id IS NULL OR cm.first_unread_id > uccm.last_unread_mention_when_emailed_id)
AND (
(cc.chatable_type = 'DirectMessage' AND eu.allow_private_messages) OR
(cc.chatable_type = 'Category' AND uccm.following AND (n.id IS NULL OR NOT n.read))
)
GROUP BY uccm.user_id
SQL
end
end