Add single column indexes and foreign keys

db/migrate/20170424131911_create_related_issues_table.rb

@@ -5,12 +5,15 @@ class CreateRelatedIssuesTable < ActiveRecord::Migration
 
   def change
     create_table :related_issues do |t|
-      t.integer :issue_id, null: false
-      t.integer :related_issue_id, null: false
+      t.integer :issue_id, null: false, index: true
+      t.integer :related_issue_id, null: false, index: true
 
       t.timestamps null: true
     end
 
     add_index :related_issues, [:issue_id, :related_issue_id], unique: true
+
+    add_foreign_key :related_issues, :issues, column: :issue_id
+    add_foreign_key :related_issues, :issues, column: :related_issue_id
   end
 end

db/schema.rb

@@ -1312,6 +1312,8 @@ ActiveRecord::Schema.define(version: 20170602003304) do
   end
 
   add_index "related_issues", ["issue_id", "related_issue_id"], name: "index_related_issues_on_issue_id_and_related_issue_id", unique: true, using: :btree
+  add_index "related_issues", ["issue_id"], name: "index_related_issues_on_issue_id", using: :btree
+  add_index "related_issues", ["related_issue_id"], name: "index_related_issues_on_related_issue_id", using: :btree
 
   create_table "releases", force: :cascade do |t|
     t.string "tag"
@@ -1745,6 +1747,8 @@ ActiveRecord::Schema.define(version: 20170602003304) do
   add_foreign_key "protected_tag_create_access_levels", "namespaces", column: "group_id"
   add_foreign_key "protected_tag_create_access_levels", "protected_tags"
   add_foreign_key "protected_tag_create_access_levels", "users"
+  add_foreign_key "related_issues", "issues"
+  add_foreign_key "related_issues", "issues", column: "related_issue_id"
   add_foreign_key "remote_mirrors", "projects"
   add_foreign_key "subscriptions", "projects", on_delete: :cascade
   add_foreign_key "system_note_metadata", "notes", name: "fk_d83a918cb1", on_delete: :cascade