Reuse runners per user and execution environment

Co-authored-by: Jan-Eric Hellenberg <jan-eric.hellenberg@student.hpi.uni-potsdam.de>
Co-authored-by: Maximilian Pass <maximilian.pass@student.hpi.uni-potsdam.de>

db/migrate/20210415064948_create_runners.rb

@@ -0,0 +1,14 @@
+class CreateRunners < ActiveRecord::Migration[5.2]
+  def change
+    create_table :runners do |t|
+      t.string :runner_id
+      t.references :execution_environment
+      t.references :user, polymorphic: true
+      t.integer :time_limit
+      t.float :waiting_time
+      t.datetime :last_used
+
+      t.timestamps
+    end
+  end
+end

db/schema.rb

@@ -339,6 +339,20 @@ ActiveRecord::Schema.define(version: 2021_05_12_133612) do
     t.index ["user_id", "user_type", "created_at"], name: "index_rfc_on_user_and_created_at", order: { created_at: :desc }
   end
 
+  create_table "runners", force: :cascade do |t|
+    t.string "runner_id"
+    t.bigint "execution_environment_id"
+    t.string "user_type"
+    t.bigint "user_id"
+    t.integer "time_limit"
+    t.float "waiting_time"
+    t.datetime "last_used"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["execution_environment_id"], name: "index_runners_on_execution_environment_id"
+    t.index ["user_type", "user_id"], name: "index_runners_on_user_type_and_user_id"
+  end
+
   create_table "searches", id: :serial, force: :cascade do |t|
     t.integer "exercise_id", null: false
     t.integer "user_id", null: false