Add index names to migrations

db/migrate/20200914104642_modify_merge_request_api_index.rb

@@ -11,10 +11,10 @@ class ModifyMergeRequestApiIndex < ActiveRecord::Migration[6.0]
   disable_ddl_transaction!
 
   def up
-    add_concurrent_index :merge_requests, [:target_project_id, :created_at, :id]
+    add_concurrent_index :merge_requests, [:target_project_id, :created_at, :id], name: :index_merge_requests_on_target_project_id_and_created_at_and_id
   end
 
   def down
-    remove_concurrent_index :merge_requests, [:target_project_id, :created_at, :id]
+    remove_concurrent_index :merge_requests, [:target_project_id, :created_at, :id], name: :index_merge_requests_on_target_project_id_and_created_at_and_id
   end
 end

db/migrate/20200914105202_remove_old_merge_request_api_index.rb

@@ -8,10 +8,10 @@ class RemoveOldMergeRequestApiIndex < ActiveRecord::Migration[6.0]
   disable_ddl_transaction!
 
   def up
-    remove_concurrent_index :merge_requests, [:target_project_id, :created_at]
+    remove_concurrent_index :merge_requests, [:target_project_id, :created_at], name: :index_merge_requests_target_project_id_created_at
   end
 
   def down
-    add_concurrent_index :merge_requests, [:target_project_id, :created_at]
+    add_concurrent_index :merge_requests, [:target_project_id, :created_at], name: :index_merge_requests_target_project_id_created_at
   end
 end