add unique indexes to gpg_keys

db/migrate/20170222111732_create_gpg_keys.rb

@@ -12,7 +12,8 @@ class CreateGpgKeys < ActiveRecord::Migration
 
       t.text :key
 
-      t.index :primary_keyid, length: Gitlab::Database.mysql? ? 20 : nil
+      t.index :primary_keyid, unique: true, length: Gitlab::Database.mysql? ? 20 : nil
+      t.index :fingerprint, unique: true, length: Gitlab::Database.mysql? ? 20 : nil
     end
   end
 end

db/schema.rb

@@ -549,7 +549,8 @@ ActiveRecord::Schema.define(version: 20170725145659) do
     t.text "key"
   end
 
-  add_index "gpg_keys", ["primary_keyid"], name: "index_gpg_keys_on_primary_keyid", using: :btree
+  add_index "gpg_keys", ["fingerprint"], name: "index_gpg_keys_on_fingerprint", unique: true, using: :btree
+  add_index "gpg_keys", ["primary_keyid"], name: "index_gpg_keys_on_primary_keyid", unique: true, using: :btree
   add_index "gpg_keys", ["user_id"], name: "index_gpg_keys_on_user_id", using: :btree
 
   create_table "gpg_signatures", force: :cascade do |t|