From 3921691319ff80b03ed8927d56b078d3fffc936a Mon Sep 17 00:00:00 2001
From: Noah Petherbridge <root@kirsle.net>
Date: Sun, 25 Aug 2024 20:43:22 -0700
Subject: [PATCH] Optimize SQL: CountLikesReceived

---
 pkg/models/like.go | 42 ++++++++++++++++++++++++++++--------------
 1 file changed, 28 insertions(+), 14 deletions(-)

diff --git a/pkg/models/like.go b/pkg/models/like.go
index 62bd02b..da85568 100644
--- a/pkg/models/like.go
+++ b/pkg/models/like.go
@@ -77,20 +77,34 @@ func CountLikesGiven(user *User) int64 {
 // CountLikesReceived by a user.
 func CountLikesReceived(user *User) int64 {
 	var count int64
-	DB.Model(&Like{}).Joins(
-		"LEFT OUTER JOIN photos ON (likes.table_name = 'photos' AND likes.table_id = photos.id)",
-	).Joins(
-		"LEFT OUTER JOIN users ON (likes.table_name = 'users' AND likes.table_id = users.id)",
-	).Joins(
-		"LEFT OUTER JOIN comments ON (likes.table_name = 'comments' AND likes.table_id = comments.id)",
-	).Where(`
-		(likes.table_name = 'photos' AND photos.user_id = ?)
-		OR
-		(likes.table_name = 'users' AND likes.table_id = ?)
-		OR
-		(likes.table_name = 'comments' AND comments.user_id = ?)`,
-		user.ID, user.ID, user.ID,
-	).Count(&count)
+
+	// Do a UNION query as it's more efficient than joining Likes to all the other tables.
+	result := DB.Raw(`
+		SELECT sum(c) FROM (
+			SELECT count(*) AS c
+			FROM likes
+			WHERE likes.table_name = 'users' AND likes.table_id = ?
+
+			UNION
+
+			SELECT count(*) AS c
+			FROM likes
+			JOIN photos ON (likes.table_name='photos' AND likes.table_id=photos.id)
+			WHERE photos.user_id = ?
+
+			UNION
+
+			SELECT count(*) AS c
+			FROM likes
+			JOIN comments ON (likes.table_name = 'comments' AND likes.table_id=comments.id)
+			WHERE comments.user_id = ?
+		) AS c
+	`, user.ID, user.ID, user.ID).Scan(&count)
+
+	if result.Error != nil {
+		log.Error("CountLikesReceived: %s", result.Error)
+	}
+
 	return count
 }