From d9714c21c80ab3b8ff68a5520d8086aa8e91588f Mon Sep 17 00:00:00 2001
From: Guo Xiang Tan <tgx_world@hotmail.com>
Date: Fri, 15 Sep 2017 22:21:05 +0800
Subject: [PATCH] Revert "PERF: Avoid unnecessary expensive joins if possible."

This reverts commit f3fadf41b7d723265094bb90203226941defce58.

* This ended up exposing group pms to users that are not part
  of a group.
---
 lib/topic_query.rb | 89 ++++++++++++++++++++--------------------------
 1 file changed, 38 insertions(+), 51 deletions(-)

diff --git a/lib/topic_query.rb b/lib/topic_query.rb
index a751fad530b..afadc2ddbbd 100644
--- a/lib/topic_query.rb
+++ b/lib/topic_query.rb
@@ -744,60 +744,53 @@ class TopicQuery
     end
 
     def related_messages_user(params)
-      messages = messages_for_user.limit(params[:count])
-      messages = allowed_messages(messages, params)
+      user_ids = ((params[:target_user_ids] || []) << -10)
+      user_ids = ActiveRecord::Base.send(:sanitize_sql_array, user_ids.join(','))
+      group_ids = (((params[:target_group_ids] - params[:my_group_ids]) || []) << -10)
+      group_ids = ActiveRecord::Base.send(:sanitize_sql_array, group_ids.join(','))
+
+      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)
-      messages = messages_for_groups_or_user(params[:my_group_ids]).limit(params[:count])
-      messages = allowed_messages(messages, params)
-    end
+      messages_for_groups_or_user(params[:my_group_ids])
+        .limit(params[:count])
+        .where('topics.id IN (
+                SELECT ta.topic_id
+                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])
 
-    def allowed_messages(messages, params)
-      user_ids = (params[:target_user_ids] || [])
-      group_ids = ((params[:target_group_ids] - params[:my_group_ids]) || [])
-
-      if user_ids.present?
-        messages =
-          messages.joins("
-            LEFT JOIN topic_allowed_users ta2
-            ON topics.id = ta2.topic_id
-            AND ta2.user_id IN (#{sanitize_sql_array(user_ids)})
-          ")
-      end
-
-      if group_ids.present?
-        messages =
-          messages.joins("
-            LEFT JOIN topic_allowed_groups tg2
-            ON topics.id = tg2.topic_id
-            AND tg2.group_id IN (#{sanitize_sql_array(group_ids)})
-          ")
-      end
-
-      messages =
-        if user_ids.present? && group_ids.present?
-          messages.where("ta2.topic_id IS NOT NULL OR tg2.topic_id IS NOT NULL")
-        elsif user_ids.present?
-          messages.where("ta2.topic_id IS NOT NULL")
-        elsif group_ids.present?
-          messages.where("tg2.topic_id IS NOT NULL")
-        end
     end
 
     def messages_for_groups_or_user(group_ids)
       if group_ids.present?
         base_messages
-          .joins("
-            LEFT JOIN (
-              SELECT * FROM topic_allowed_groups _tg
-              LEFT JOIN group_users gu
-              ON gu.user_id = #{@user.id.to_i}
-              AND gu.group_id = _tg.group_id
-              AND gu.group_id IN (#{sanitize_sql_array(group_ids)})
-            ) tg ON topics.id = tg.topic_id
-          ")
-          .where("tg.topic_id IS NOT NULL")
+          .where('topics.id IN (
+                                  SELECT topic_id
+                                    FROM topic_allowed_groups tg
+                                    JOIN group_users gu ON gu.user_id = :user_id AND gu.group_id = tg.group_id
+                                    WHERE gu.group_id IN (:group_ids)
+                 )', user_id: @user.id, group_ids: group_ids)
       else
         messages_for_user
       end
@@ -854,10 +847,4 @@ class TopicQuery
 
       result.order('topics.bumped_at DESC')
     end
-
-  private
-
-    def sanitize_sql_array(input)
-      ActiveRecord::Base.send(:sanitize_sql_array, input.join(','))
-    end
 end