diff --git a/db/schema.rb b/db/schema.rb
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -2,19 +2,19 @@
 # of editing this file, please use the migrations feature of Active Record to
 # incrementally modify your database, and then regenerate this schema definition.
 #
-# Note that this schema.rb definition is the authoritative source for your
-# database schema. If you need to create the application database on another
-# system, you should be using db:schema:load, not running all the migrations
-# from scratch. The latter is a flawed and unsustainable approach (the more migrations
-# you'll amass, the slower it'll run and the greater likelihood for issues).
+# This file is the source Rails uses to define your schema when running `bin/rails
+# db:schema:load`. When creating a new database, `bin/rails db:schema:load` tends to
+# be faster and is potentially less error prone than running all of your
+# migrations from scratch. Old migrations may fail to apply correctly if those
+# migrations use external dependencies or application code.
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2021_08_09_105935) do
+ActiveRecord::Schema.define(version: 2022_02_04_080936) do
 
-  create_table "announcements", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "announcements", id: :integer, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
     t.string "author"
-    t.text "body", limit: 16777215
+    t.text "body"
     t.boolean "published"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
@@ -25,7 +25,7 @@
     t.boolean "on_nav_bar", default: false
   end
 
-  create_table "contests", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "contests", id: :integer, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
     t.string "title"
     t.boolean "enabled"
     t.datetime "created_at", null: false
@@ -33,39 +33,39 @@
     t.string "name"
   end
 
-  create_table "contests_problems", id: false, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "contests_problems", id: false, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
     t.integer "contest_id"
     t.integer "problem_id"
   end
 
-  create_table "contests_users", id: false, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "contests_users", id: false, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
     t.integer "contest_id"
     t.integer "user_id"
   end
 
-  create_table "countries", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "countries", id: :integer, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
     t.string "name"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
   end
 
-  create_table "descriptions", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
-    t.text "body", limit: 16777215
+  create_table "descriptions", id: :integer, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
+    t.text "body"
     t.boolean "markdowned"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
   end
 
-  create_table "grader_configurations", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "grader_configurations", id: :integer, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
     t.string "key"
     t.string "value_type"
     t.string "value"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
-    t.text "description", limit: 16777215
+    t.text "description"
   end
 
-  create_table "grader_processes", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "grader_processes", id: :integer, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
     t.string "host"
     t.integer "pid"
     t.string "mode"
@@ -78,25 +78,25 @@
     t.index ["host", "pid"], name: "index_grader_processes_on_ip_and_pid"
   end
 
-  create_table "groups", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
+  create_table "groups", id: :integer, charset: "latin1", force: :cascade do |t|
     t.string "name"
     t.string "description"
     t.boolean "enabled", default: true
   end
 
-  create_table "groups_problems", id: false, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
+  create_table "groups_problems", id: false, charset: "latin1", force: :cascade do |t|
     t.integer "problem_id", null: false
     t.integer "group_id", null: false
     t.index ["group_id", "problem_id"], name: "index_groups_problems_on_group_id_and_problem_id"
   end
 
-  create_table "groups_users", options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
+  create_table "groups_users", charset: "latin1", force: :cascade do |t|
     t.integer "group_id", null: false
     t.integer "user_id", null: false
     t.index ["user_id", "group_id"], name: "index_groups_users_on_user_id_and_group_id"
   end
 
-  create_table "heart_beats", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
+  create_table "heart_beats", id: :integer, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
     t.integer "user_id"
     t.string "ip_address"
     t.datetime "created_at", null: false
@@ -105,14 +105,14 @@
     t.index ["updated_at"], name: "index_heart_beats_on_updated_at"
   end
 
-  create_table "languages", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "languages", id: :integer, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
     t.string "name", limit: 10
     t.string "pretty_name"
     t.string "ext", limit: 10
     t.string "common_ext"
   end
 
-  create_table "logins", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
+  create_table "logins", id: :integer, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
     t.integer "user_id"
     t.string "ip_address"
     t.datetime "created_at", null: false
@@ -120,18 +120,18 @@
     t.index ["user_id"], name: "index_logins_on_user_id"
   end
 
-  create_table "messages", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "messages", id: :integer, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
     t.integer "sender_id"
     t.integer "receiver_id"
     t.integer "replying_message_id"
-    t.text "body", limit: 16777215
+    t.text "body"
     t.boolean "replied"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
   end
 
-  create_table "problems", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
-    t.string "name", limit: 100
+  create_table "problems", id: :integer, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
+    t.string "name", limit: 30
     t.string "full_name"
     t.integer "full_score"
     t.date "date_added"
@@ -142,9 +142,10 @@
     t.boolean "output_only"
     t.string "description_filename"
     t.boolean "view_testcase"
+    t.integer "difficulty"
   end
 
-  create_table "problems_tags", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
+  create_table "problems_tags", id: :integer, charset: "latin1", force: :cascade do |t|
     t.integer "problem_id"
     t.integer "tag_id"
     t.index ["problem_id", "tag_id"], name: "index_problems_tags_on_problem_id_and_tag_id", unique: true
@@ -152,37 +153,37 @@
     t.index ["tag_id"], name: "index_problems_tags_on_tag_id"
   end
 
-  create_table "rights", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "rights", id: :integer, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
     t.string "name"
     t.string "controller"
     t.string "action"
   end
 
-  create_table "rights_roles", id: false, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "rights_roles", id: false, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
     t.integer "right_id"
     t.integer "role_id"
     t.index ["role_id"], name: "index_rights_roles_on_role_id"
   end
 
-  create_table "roles", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "roles", id: :integer, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
     t.string "name"
   end
 
-  create_table "roles_users", id: false, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "roles_users", id: false, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
     t.integer "role_id"
     t.integer "user_id"
     t.index ["user_id"], name: "index_roles_users_on_user_id"
   end
 
-  create_table "sessions", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "sessions", id: :integer, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
     t.string "session_id"
-    t.text "data", limit: 16777215
+    t.text "data"
     t.datetime "updated_at"
     t.index ["session_id"], name: "index_sessions_on_session_id"
     t.index ["updated_at"], name: "index_sessions_on_updated_at"
   end
 
-  create_table "sites", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "sites", id: :integer, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
     t.string "name"
     t.boolean "started"
     t.datetime "start_time"
@@ -192,37 +193,38 @@
     t.string "password"
   end
 
-  create_table "submission_view_logs", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
+  create_table "submission_view_logs", id: :integer, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
     t.integer "user_id"
     t.integer "submission_id"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
   end
 
-  create_table "submissions", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "submissions", id: :integer, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
     t.integer "user_id"
     t.integer "problem_id"
     t.integer "language_id"
-    t.text "source", limit: 16777215
+    t.text "source", size: :medium
     t.binary "binary"
     t.datetime "submitted_at"
     t.datetime "compiled_at"
-    t.text "compiler_message", limit: 16777215
+    t.text "compiler_message"
     t.datetime "graded_at"
     t.integer "points"
-    t.text "grader_comment", limit: 16777215
+    t.text "grader_comment"
     t.integer "number"
     t.string "source_filename"
     t.float "max_runtime"
     t.integer "peak_memory"
     t.integer "effective_code_length"
     t.string "ip_address"
+    t.integer "tag", default: 0
     t.index ["submitted_at"], name: "index_submissions_on_submitted_at"
     t.index ["user_id", "problem_id", "number"], name: "index_submissions_on_user_id_and_problem_id_and_number", unique: true
     t.index ["user_id", "problem_id"], name: "index_submissions_on_user_id_and_problem_id"
   end
 
-  create_table "tags", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
+  create_table "tags", id: :integer, charset: "latin1", force: :cascade do |t|
     t.string "name", null: false
     t.text "description"
     t.boolean "public"
@@ -230,7 +232,7 @@
     t.datetime "updated_at", null: false
   end
 
-  create_table "tasks", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "tasks", id: :integer, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
     t.integer "submission_id"
     t.datetime "created_at"
     t.integer "status"
@@ -239,15 +241,15 @@
     t.index ["submission_id"], name: "index_tasks_on_submission_id"
   end
 
-  create_table "test_pairs", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "test_pairs", id: :integer, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
     t.integer "problem_id"
-    t.text "input", limit: 4294967295
-    t.text "solution", limit: 4294967295
+    t.text "input", size: :medium
+    t.text "solution", size: :medium
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
   end
 
-  create_table "test_requests", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "test_requests", id: :integer, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
     t.integer "user_id"
     t.integer "problem_id"
     t.integer "submission_id"
@@ -258,7 +260,7 @@
     t.datetime "updated_at", null: false
     t.datetime "submitted_at"
     t.datetime "compiled_at"
-    t.text "compiler_message", limit: 16777215
+    t.text "compiler_message"
     t.datetime "graded_at"
     t.string "grader_comment"
     t.datetime "created_at", null: false
@@ -268,19 +270,19 @@
     t.index ["user_id", "problem_id"], name: "index_test_requests_on_user_id_and_problem_id"
   end
 
-  create_table "testcases", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
+  create_table "testcases", id: :integer, charset: "latin1", force: :cascade do |t|
     t.integer "problem_id"
     t.integer "num"
     t.integer "group"
     t.integer "score"
-    t.text "input", limit: 4294967295
-    t.text "sol", limit: 4294967295
-    t.datetime "created_at", null: false
-    t.datetime "updated_at", null: false
+    t.text "input", size: :long
+    t.text "sol", size: :long
+    t.datetime "created_at"
+    t.datetime "updated_at"
     t.index ["problem_id"], name: "index_testcases_on_problem_id"
   end
 
-  create_table "user_contest_stats", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "user_contest_stats", id: :integer, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
     t.integer "user_id"
     t.datetime "started_at"
     t.datetime "created_at", null: false
@@ -288,7 +290,7 @@
     t.boolean "forced_logout"
   end
 
-  create_table "users", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "users", id: :integer, charset: "utf8", collation: "utf8_unicode_ci", force: :cascade do |t|
     t.string "login", limit: 50
     t.string "full_name"
     t.string "hashed_password"
@@ -300,10 +302,10 @@
     t.boolean "activated", default: false
     t.datetime "created_at"
     t.datetime "updated_at"
-    t.string "section"
     t.boolean "enabled", default: true
     t.string "remark"
     t.string "last_ip"
+    t.string "section"
     t.integer "default_language"
     t.index ["login"], name: "index_users_on_login", unique: true
   end