From c2f8aeeeccaef9598c7ddb10ee29e51c251881ab Mon Sep 17 00:00:00 2001
From: Ian Morland <ian@morland.me>
Date: Fri, 6 Mar 2020 14:12:34 +0000
Subject: [PATCH] Improve performance of subqueries (#75)

---
 extensions/tags/src/Access/DiscussionPolicy.php  | 14 ++++++--------
 extensions/tags/src/Gambit/TagGambit.php         | 16 +++++++---------
 .../src/Listener/FilterDiscussionListByTags.php  |  7 +++----
 3 files changed, 16 insertions(+), 21 deletions(-)

diff --git a/extensions/tags/src/Access/DiscussionPolicy.php b/extensions/tags/src/Access/DiscussionPolicy.php
index e131cee6e..2f23ecb01 100755
--- a/extensions/tags/src/Access/DiscussionPolicy.php
+++ b/extensions/tags/src/Access/DiscussionPolicy.php
@@ -76,11 +76,10 @@ class DiscussionPolicy extends AbstractPolicy
     public function find(User $actor, Builder $query)
     {
         // Hide discussions which have tags that the user is not allowed to see.
-        $query->whereNotExists(function ($query) use ($actor) {
-            return $query->selectRaw('1')
+        $query->whereNotIn('discussions.id', function ($query) use ($actor) {
+            return $query->select('discussion_id')
                 ->from('discussion_tag')
-                ->whereIn('tag_id', Tag::getIdsWhereCannot($actor, 'viewDiscussions'))
-                ->whereColumn('discussions.id', 'discussion_id');
+                ->whereIn('tag_id', Tag::getIdsWhereCannot($actor, 'viewDiscussions'));
         });
 
         // Hide discussions with no tags if the user doesn't have that global
@@ -100,11 +99,10 @@ class DiscussionPolicy extends AbstractPolicy
         // If a discussion requires a certain permission in order for it to be
         // visible, then we can check if the user has been granted that
         // permission for any of the discussion's tags.
-        $query->whereExists(function ($query) use ($actor, $ability) {
-            return $query->selectRaw('1')
+        $query->whereIn('discussions.id', function ($query) use ($actor, $ability) {
+            return $query->select('discussion_id')
                 ->from('discussion_tag')
-                ->whereIn('tag_id', Tag::getIdsWhereCan($actor, 'discussion.'.$ability))
-                ->whereColumn('discussions.id', 'discussion_id');
+                ->whereIn('tag_id', Tag::getIdsWhereCan($actor, 'discussion.'.$ability));
         });
     }
 
diff --git a/extensions/tags/src/Gambit/TagGambit.php b/extensions/tags/src/Gambit/TagGambit.php
index a2381a8ff..8dd5a1728 100644
--- a/extensions/tags/src/Gambit/TagGambit.php
+++ b/extensions/tags/src/Gambit/TagGambit.php
@@ -43,19 +43,17 @@ class TagGambit extends AbstractRegexGambit
         $search->getQuery()->where(function ($query) use ($slugs, $negate) {
             foreach ($slugs as $slug) {
                 if ($slug === 'untagged') {
-                    $query->orWhereExists(function ($query) {
-                        $query->selectRaw('1')
-                              ->from('discussion_tag')
-                              ->whereColumn('discussions.id', 'discussion_id');
+                    $query->orWhereIn('discussions.id', function ($query) {
+                        $query->select('discussion_id')
+                            ->from('discussion_tag');
                     }, ! $negate);
                 } else {
                     $id = $this->tags->getIdForSlug($slug);
 
-                    $query->orWhereExists(function ($query) use ($id) {
-                        $query->selectRaw('1')
-                              ->from('discussion_tag')
-                              ->whereColumn('discussions.id', 'discussion_id')
-                              ->where('tag_id', $id);
+                    $query->orWhereIn('discussions.id', function ($query) use ($id) {
+                        $query->select('discussion_id')
+                            ->from('discussion_tag')
+                            ->where('tag_id', $id);
                     }, $negate);
                 }
             }
diff --git a/extensions/tags/src/Listener/FilterDiscussionListByTags.php b/extensions/tags/src/Listener/FilterDiscussionListByTags.php
index b7ff59257..9fc8b9bf7 100755
--- a/extensions/tags/src/Listener/FilterDiscussionListByTags.php
+++ b/extensions/tags/src/Listener/FilterDiscussionListByTags.php
@@ -45,11 +45,10 @@ class FilterDiscussionListByTags
             return;
         }
 
-        $query->whereNotExists(function ($query) {
-            return $query->selectRaw('1')
+        $query->whereNotIn('discussions.id', function ($query) {
+            return $query->select('discussion_id')
                 ->from('discussion_tag')
-                ->whereIn('tag_id', Tag::where('is_hidden', 1)->pluck('id'))
-                ->whereColumn('discussions.id', 'discussion_id');
+                ->whereIn('tag_id', Tag::where('is_hidden', 1)->pluck('id'));
         });
     }
 }