From cbd021db15aa51db807b55d0527a34ce73e424c8 Mon Sep 17 00:00:00 2001
From: Krzysztof Kotlarek <kotlarek.krzysztof@gmail.com>
Date: Fri, 10 Feb 2023 11:14:22 +1100
Subject: [PATCH] FIX: add index to sidebar_section_link (#20234)

Index on linkable_type and linkable_id should increase performance of this subquery https://github.com/discourse/discourse/blob/main/app/services/sidebar_site_settings_backfiller.rb#L86

Also, distinct is removing duplicates which are unnecessary.
---
 app/models/sidebar_section_link.rb            |  3 ++-
 .../sidebar_site_settings_backfiller.rb       |  2 +-
 ...linkable_index_to_sidebar_section_links.rb | 22 +++++++++++++++++++
 3 files changed, 25 insertions(+), 2 deletions(-)
 create mode 100644 db/migrate/20230209222225_add_linkable_index_to_sidebar_section_links.rb

diff --git a/app/models/sidebar_section_link.rb b/app/models/sidebar_section_link.rb
index ab89b950f9c..c9a799b89d0 100644
--- a/app/models/sidebar_section_link.rb
+++ b/app/models/sidebar_section_link.rb
@@ -40,5 +40,6 @@ end
 #
 # Indexes
 #
-#  idx_unique_sidebar_section_links  (user_id,linkable_type,linkable_id) UNIQUE
+#  idx_unique_sidebar_section_links                              (user_id,linkable_type,linkable_id) UNIQUE
+#  index_sidebar_section_links_on_linkable_type_and_linkable_id  (linkable_type,linkable_id)
 #
diff --git a/app/services/sidebar_site_settings_backfiller.rb b/app/services/sidebar_site_settings_backfiller.rb
index 7fe13f8162b..fae0f500512 100644
--- a/app/services/sidebar_site_settings_backfiller.rb
+++ b/app/services/sidebar_site_settings_backfiller.rb
@@ -81,7 +81,7 @@ class SidebarSiteSettingsBackfiller
       FROM users
       WHERE users.id NOT IN (
         SELECT
-          sidebar_section_links.user_id
+          DISTINCT(sidebar_section_links.user_id)
         FROM sidebar_section_links
         WHERE sidebar_section_links.linkable_type = '#{@linkable_klass.to_s}'
         AND sidebar_section_links.linkable_id IN (#{@added_ids.join(",")})
diff --git a/db/migrate/20230209222225_add_linkable_index_to_sidebar_section_links.rb b/db/migrate/20230209222225_add_linkable_index_to_sidebar_section_links.rb
new file mode 100644
index 00000000000..3cdcf23466d
--- /dev/null
+++ b/db/migrate/20230209222225_add_linkable_index_to_sidebar_section_links.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+class AddLinkableIndexToSidebarSectionLinks < ActiveRecord::Migration[7.0]
+  disable_ddl_transaction!
+
+  def up
+    execute <<~SQL
+    DROP INDEX CONCURRENTLY IF EXISTS index_sidebar_section_links_on_linkable_type_and_linkable_id
+    SQL
+
+    execute <<~SQL
+    CREATE INDEX CONCURRENTLY index_sidebar_section_links_on_linkable_type_and_linkable_id
+    ON sidebar_section_links (linkable_type,linkable_id)
+    SQL
+  end
+
+  def down
+    execute <<~SQL
+    DROP INDEX CONCURRENTLY IF EXISTS index_sidebar_section_links_on_linkable_type_and_linkable_id
+    SQL
+  end
+end