From c71da3f3352159f02276c9a49f1ed8c54c75010d Mon Sep 17 00:00:00 2001
From: Daniel Waterworth <me@danielwaterworth.com>
Date: Tue, 8 Oct 2019 14:00:05 +0100
Subject: [PATCH] FIX: Add unique index to prevent duplicate slugs for
 categories

---
 app/models/category.rb                               |  1 +
 ...1008124357_add_unique_index_categories_on_slug.rb | 12 ++++++++++++
 2 files changed, 13 insertions(+)
 create mode 100644 db/migrate/20191008124357_add_unique_index_categories_on_slug.rb

diff --git a/app/models/category.rb b/app/models/category.rb
index a903c8f3664..db500e6ff67 100644
--- a/app/models/category.rb
+++ b/app/models/category.rb
@@ -890,4 +890,5 @@ end
 #  index_categories_on_search_priority         (search_priority)
 #  index_categories_on_topic_count             (topic_count)
 #  unique_index_categories_on_name             (COALESCE(parent_category_id, '-1'::integer), name) UNIQUE
+#  unique_index_categories_on_slug             (COALESCE(parent_category_id, '-1'::integer), slug) UNIQUE
 #
diff --git a/db/migrate/20191008124357_add_unique_index_categories_on_slug.rb b/db/migrate/20191008124357_add_unique_index_categories_on_slug.rb
new file mode 100644
index 00000000000..5ee97c64826
--- /dev/null
+++ b/db/migrate/20191008124357_add_unique_index_categories_on_slug.rb
@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+class AddUniqueIndexCategoriesOnSlug < ActiveRecord::Migration[6.0]
+  def change
+    add_index(
+      :categories,
+      'COALESCE(parent_category_id, -1), slug',
+      name: 'unique_index_categories_on_slug',
+      unique: true
+    )
+  end
+end