Remove redundant index

changelogs/unreleased/55360-redundant-index-in-the-releases-table_v2.yml

+---
+title: Removed redundant index on releases table
+merge_request: 31487
+author:
+type: removed

db/migrate/20190805140353_remove_rendundant_index_from_releases.rb

+# frozen_string_literal: true
+
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class RemoveRendundantIndexFromReleases < ActiveRecord::Migration[5.2]
+  include Gitlab::Database::MigrationHelpers
+
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    remove_concurrent_index :releases, :project_id
+  end
+
+  def down
+    add_concurrent_index :releases, :project_id
+  end
+end

db/schema.rb

@@ -3015,7 +3015,6 @@ ActiveRecord::Schema.define(version: 2019_08_15_093949) do
     t.datetime_with_timezone "released_at", null: false
     t.index ["author_id"], name: "index_releases_on_author_id"
     t.index ["project_id", "tag"], name: "index_releases_on_project_id_and_tag"
-    t.index ["project_id"], name: "index_releases_on_project_id"
   end
   create_table "remote_mirrors", id: :serial, force: :cascade do |t|