PERF: Avoid `NOT IN (<subquery>>` which can get really slow.

```
EXPLAIN ANALYZE SELECT  "topics".*
FROM "topics" LEFT JOIN topic_users tu ON topics.id = tu.topic_id AND
tu.user_id = 13455
WHERE ("topics"."deleted_at" IS NULL)
AND (topics.archetype = 'private_message')
AND (
  topics.id IN (
    SELECT topic_id
    FROM topic_allowed_users
    WHERE user_id = 13455
   )
)
AND (
  topics.id IN (
    SELECT ta.topic_id
    FROM topic_allowed_users ta
    WHERE ta.user_id IN (2,1995,8307,17621,22980,-10)
  )
  OR
  topics.id IN (
    SELECT tg.topic_id
    FROM topic_allowed_groups tg
    WHERE tg.group_id IN (-10)
  )
)
AND (topics.id NOT IN (68559,60069,42145))
AND "topics"."visible" = 't'
ORDER BY topics.bumped_at
DESC LIMIT 5;
```

Planning time: 1.196 ms
Execution time: 21.176 ms

```
EXPLAIN ANALYZE SELECT  "topics".*
FROM "topics"
LEFT JOIN topic_users tu ON topics.id = tu.topic_id AND tu.user_id =
13455
LEFT JOIN topic_allowed_users ta ON topics.id = ta.topic_id AND
ta.user_id = 13455
LEFT JOIN topic_allowed_users ta2 ON topics.id = ta2.topic_id AND
ta2.user_id IN (2,1995,8307,17621,22980,-10)
LEFT JOIN topic_allowed_groups tg ON topics.id = tg.topic_id AND
tg.group_id IN (-10)
WHERE ("topics"."deleted_at" IS NULL)
AND (topics.archetype = 'private_message')
AND (ta.topic_id IS NOT NULL)
AND (ta2.topic_id IS NOT NULL OR tg.topic_id IS NOT NULL)
AND (topics.id NOT IN (68559,60069,42145))
AND "topics"."visible" = 't'
ORDER BY topics.bumped_at DESC
LIMIT 5;
```

Planning time: 1.792 ms
Execution time: 2.546 ms

lib/topic_query.rb

@@ -107,8 +107,13 @@ class TopicQuery
       if topic.private_message?
 
         group_ids = topic.topic_allowed_groups
-          .where('group_id IN (SELECT group_id FROM group_users WHERE user_id = :user_id)', user_id: @user.id)
+          .joins("
+            LEFT JOIN group_users gu
+            ON topic_allowed_groups.group_id = gu.group_id
+            AND user_id = #{@user.id.to_i}
+          ")
           .pluck(:group_id)
+
         {
           topic: topic,
           my_group_ids: group_ids,
@@ -743,21 +748,24 @@ class TopicQuery
     end
 
     def related_messages_user(params)
-      messages_for_user
+      user_ids = ((params[:target_user_ids] || []) << -10)
-        .limit(params[:count])
+      user_ids = ActiveRecord::Base.send(:sanitize_sql_array, user_ids.join(','))
-        .where('topics.id IN (
+      group_ids = (((params[:target_group_ids] - params[:my_group_ids]) || []) << -10)
-                SELECT ta.topic_id
+      group_ids = ActiveRecord::Base.send(:sanitize_sql_array, group_ids.join(','))
-                FROM topic_allowed_users ta
-                WHERE ta.user_id IN (:user_ids)
-              ) OR
-                topics.id IN (
-                  SELECT tg.topic_id
-                  FROM topic_allowed_groups tg
-                  WHERE tg.group_id IN (:group_ids)
-              )
-              ', user_ids: (params[:target_user_ids] || []) + [-10],
-                 group_ids: ((params[:target_group_ids] - params[:my_group_ids]) || []) + [-10])
 
+      result = messages_for_user
+        .limit(params[:count])
+        .joins("
+          LEFT JOIN topic_allowed_users ta2
+          ON topics.id = ta2.topic_id
+          AND ta2.user_id IN (#{user_ids})",
+        )
+        .joins("
+          LEFT JOIN topic_allowed_groups tg
+          ON topics.id = tg.topic_id
+          AND tg.group_id IN (#{group_ids})",
+        )
+        .where("ta2.topic_id IS NOT NULL OR tg.topic_id IS NOT NULL")
     end
 
     def related_messages_group(params)
@@ -793,11 +801,13 @@ class TopicQuery
     end
 
     def messages_for_user
-      base_messages.where('topics.id IN (
+      base_messages
-                                  SELECT topic_id
+        .joins("
-                                    FROM topic_allowed_users
+          LEFT JOIN topic_allowed_users ta
-                                    WHERE user_id = :user_id
+          ON topics.id = ta.topic_id
-                 )', user_id: @user.id)
+          AND ta.user_id = #{@user.id.to_i}
+        ")
+        .where("ta.topic_id IS NOT NULL")
     end
 
     def base_messages