diff --git a/db/schema.rb b/db/schema.rb
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -1,4 +1,3 @@
-# encoding: UTF-8
 # This file is auto-generated from the current state of the database. Instead
 # of editing this file, please use the migrations feature of Active Record to
 # incrementally modify your database, and then regenerate this schema definition.
@@ -11,311 +10,299 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20180612102327) do
+ActiveRecord::Schema.define(version: 2020_04_04_142959) do
 
-  create_table "announcements", force: :cascade do |t|
-    t.string   "author",       limit: 255
-    t.text     "body",         limit: 65535
-    t.boolean  "published"
-    t.datetime "created_at"
-    t.datetime "updated_at"
-    t.boolean  "frontpage",                  default: false
-    t.boolean  "contest_only",               default: false
-    t.string   "title",        limit: 255
-    t.string   "notes",        limit: 255
+  create_table "announcements", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+    t.string "author"
+    t.text "body", limit: 16777215
+    t.boolean "published"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.boolean "frontpage", default: false
+    t.boolean "contest_only", default: false
+    t.string "title"
+    t.string "notes"
   end
 
-  create_table "contests", force: :cascade do |t|
-    t.string   "title",      limit: 255
-    t.boolean  "enabled"
-    t.datetime "created_at"
-    t.datetime "updated_at"
-    t.string   "name",       limit: 255
-  end
-
-  create_table "contests_problems", id: false, force: :cascade do |t|
-    t.integer "contest_id", limit: 4
-    t.integer "problem_id", limit: 4
-  end
-
-  create_table "contests_users", id: false, force: :cascade do |t|
-    t.integer "contest_id", limit: 4
-    t.integer "user_id",    limit: 4
+  create_table "contests", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+    t.string "title"
+    t.boolean "enabled"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.string "name"
   end
 
-  create_table "countries", force: :cascade do |t|
-    t.string   "name",       limit: 255
-    t.datetime "created_at"
-    t.datetime "updated_at"
+  create_table "contests_problems", id: false, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+    t.integer "contest_id"
+    t.integer "problem_id"
   end
 
-  create_table "descriptions", force: :cascade do |t|
-    t.text     "body",       limit: 65535
-    t.boolean  "markdowned"
-    t.datetime "created_at"
-    t.datetime "updated_at"
+  create_table "contests_users", id: false, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+    t.integer "contest_id"
+    t.integer "user_id"
   end
 
-  create_table "grader_configurations", force: :cascade do |t|
-    t.string   "key",         limit: 255
-    t.string   "value_type",  limit: 255
-    t.string   "value",       limit: 255
-    t.datetime "created_at"
-    t.datetime "updated_at"
-    t.text     "description", limit: 65535
+  create_table "countries", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+    t.string "name"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
   end
 
-  create_table "grader_processes", force: :cascade do |t|
-    t.string   "host",       limit: 255
-    t.integer  "pid",        limit: 4
-    t.string   "mode",       limit: 255
-    t.boolean  "active"
-    t.datetime "created_at"
-    t.datetime "updated_at"
-    t.integer  "task_id",    limit: 4
-    t.string   "task_type",  limit: 255
-    t.boolean  "terminated"
+  create_table "descriptions", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+    t.text "body", limit: 16777215
+    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|
+    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
   end
 
-  add_index "grader_processes", ["host", "pid"], name: "index_grader_processes_on_host_and_pid", using: :btree
-
-  create_table "groups", force: :cascade do |t|
-    t.string "name",        limit: 255
-    t.string "description", limit: 255
-  end
-
-  create_table "groups_problems", id: false, force: :cascade do |t|
-    t.integer "problem_id", limit: 4, null: false
-    t.integer "group_id",   limit: 4, null: false
+  create_table "grader_processes", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+    t.string "host"
+    t.integer "pid"
+    t.string "mode"
+    t.boolean "active"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.integer "task_id"
+    t.string "task_type"
+    t.boolean "terminated"
+    t.index ["host", "pid"], name: "index_grader_processes_on_ip_and_pid"
   end
 
-  add_index "groups_problems", ["group_id", "problem_id"], name: "index_groups_problems_on_group_id_and_problem_id", using: :btree
-
-  create_table "groups_users", id: false, force: :cascade do |t|
-    t.integer "group_id", limit: 4, null: false
-    t.integer "user_id",  limit: 4, null: false
+  create_table "groups", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
+    t.string "name"
+    t.string "description"
   end
 
-  add_index "groups_users", ["user_id", "group_id"], name: "index_groups_users_on_user_id_and_group_id", using: :btree
+  create_table "groups_problems", id: false, options: "ENGINE=InnoDB DEFAULT 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 "heart_beats", force: :cascade do |t|
-    t.integer  "user_id",    limit: 4
-    t.string   "ip_address", limit: 255
-    t.datetime "created_at"
-    t.datetime "updated_at"
-    t.string   "status",     limit: 255
+  create_table "groups_users", options: "ENGINE=InnoDB DEFAULT 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
 
-  add_index "heart_beats", ["updated_at"], name: "index_heart_beats_on_updated_at", using: :btree
-
-  create_table "languages", force: :cascade do |t|
-    t.string "name",        limit: 10
-    t.string "pretty_name", limit: 255
-    t.string "ext",         limit: 10
-    t.string "common_ext",  limit: 255
+  create_table "heart_beats", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
+    t.integer "user_id"
+    t.string "ip_address"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.string "status"
+    t.index ["updated_at"], name: "index_heart_beats_on_updated_at"
   end
 
-  create_table "logins", force: :cascade do |t|
-    t.integer  "user_id",    limit: 4
-    t.string   "ip_address", limit: 255
-    t.datetime "created_at"
-    t.datetime "updated_at"
+  create_table "languages", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", 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 "messages", force: :cascade do |t|
-    t.integer  "sender_id",           limit: 4
-    t.integer  "receiver_id",         limit: 4
-    t.integer  "replying_message_id", limit: 4
-    t.text     "body",                limit: 65535
-    t.boolean  "replied"
-    t.datetime "created_at"
-    t.datetime "updated_at"
+  create_table "logins", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
+    t.integer "user_id"
+    t.string "ip_address"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
   end
 
-  create_table "problems", force: :cascade do |t|
-    t.string  "name",                 limit: 30
-    t.string  "full_name",            limit: 255
-    t.integer "full_score",           limit: 4
-    t.date    "date_added"
+  create_table "messages", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+    t.integer "sender_id"
+    t.integer "receiver_id"
+    t.integer "replying_message_id"
+    t.text "body", limit: 16777215
+    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
+    t.string "full_name"
+    t.integer "full_score"
+    t.date "date_added"
     t.boolean "available"
-    t.string  "url",                  limit: 255
-    t.integer "description_id",       limit: 4
+    t.string "url"
+    t.integer "description_id"
     t.boolean "test_allowed"
     t.boolean "output_only"
-    t.string  "description_filename", limit: 255
+    t.string "description_filename"
     t.boolean "view_testcase"
   end
 
-  create_table "problems_tags", force: :cascade do |t|
-    t.integer "problem_id", limit: 4
-    t.integer "tag_id",     limit: 4
+  create_table "problems_tags", id: :integer, options: "ENGINE=InnoDB DEFAULT 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
+    t.index ["problem_id"], name: "index_problems_tags_on_problem_id"
+    t.index ["tag_id"], name: "index_problems_tags_on_tag_id"
   end
 
-  add_index "problems_tags", ["problem_id", "tag_id"], name: "index_problems_tags_on_problem_id_and_tag_id", unique: true, using: :btree
-  add_index "problems_tags", ["problem_id"], name: "index_problems_tags_on_problem_id", using: :btree
-  add_index "problems_tags", ["tag_id"], name: "index_problems_tags_on_tag_id", using: :btree
-
-  create_table "rights", force: :cascade do |t|
-    t.string "name",       limit: 255
-    t.string "controller", limit: 255
-    t.string "action",     limit: 255
+  create_table "rights", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+    t.string "name"
+    t.string "controller"
+    t.string "action"
   end
 
-  create_table "rights_roles", id: false, force: :cascade do |t|
-    t.integer "right_id", limit: 4
-    t.integer "role_id",  limit: 4
+  create_table "rights_roles", id: false, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+    t.integer "right_id"
+    t.integer "role_id"
+    t.index ["role_id"], name: "index_rights_roles_on_role_id"
   end
 
-  add_index "rights_roles", ["role_id"], name: "index_rights_roles_on_role_id", using: :btree
-
-  create_table "roles", force: :cascade do |t|
-    t.string "name", limit: 255
+  create_table "roles", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+    t.string "name"
   end
 
-  create_table "roles_users", id: false, force: :cascade do |t|
-    t.integer "role_id", limit: 4
-    t.integer "user_id", limit: 4
+  create_table "roles_users", id: false, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+    t.integer "role_id"
+    t.integer "user_id"
+    t.index ["user_id"], name: "index_roles_users_on_user_id"
   end
 
-  add_index "roles_users", ["user_id"], name: "index_roles_users_on_user_id", using: :btree
-
-  create_table "sessions", force: :cascade do |t|
-    t.string   "session_id", limit: 255
-    t.text     "data",       limit: 65535
+  create_table "sessions", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+    t.string "session_id"
+    t.text "data", limit: 16777215
     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
 
-  add_index "sessions", ["session_id"], name: "index_sessions_on_session_id", using: :btree
-  add_index "sessions", ["updated_at"], name: "index_sessions_on_updated_at", using: :btree
+  create_table "sites", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+    t.string "name"
+    t.boolean "started"
+    t.datetime "start_time"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.integer "country_id"
+    t.string "password"
+  end
 
-  create_table "sites", force: :cascade do |t|
-    t.string   "name",       limit: 255
-    t.boolean  "started"
-    t.datetime "start_time"
-    t.datetime "created_at"
-    t.datetime "updated_at"
-    t.integer  "country_id", limit: 4
-    t.string   "password",   limit: 255
+  create_table "submission_view_logs", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", 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 "submission_view_logs", force: :cascade do |t|
-    t.integer  "user_id",       limit: 4
-    t.integer  "submission_id", limit: 4
-    t.datetime "created_at"
-    t.datetime "updated_at"
-  end
-
-  create_table "submissions", force: :cascade do |t|
-    t.integer  "user_id",               limit: 4
-    t.integer  "problem_id",            limit: 4
-    t.integer  "language_id",           limit: 4
-    t.text     "source",                limit: 16777215
-    t.binary   "binary",                limit: 65535
+  create_table "submissions", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+    t.integer "user_id"
+    t.integer "problem_id"
+    t.integer "language_id"
+    t.text "source", limit: 16777215
+    t.binary "binary"
     t.datetime "submitted_at"
     t.datetime "compiled_at"
-    t.text     "compiler_message",      limit: 65535
+    t.text "compiler_message", limit: 16777215
     t.datetime "graded_at"
-    t.integer  "points",                limit: 4
-    t.text     "grader_comment",        limit: 65535
-    t.integer  "number",                limit: 4
-    t.string   "source_filename",       limit: 255
-    t.float    "max_runtime",           limit: 24
-    t.integer  "peak_memory",           limit: 4
-    t.integer  "effective_code_length", limit: 4
-    t.string   "ip_address",            limit: 255
+    t.integer "points"
+    t.text "grader_comment", limit: 16777215
+    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.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
 
-  add_index "submissions", ["user_id", "problem_id", "number"], name: "index_submissions_on_user_id_and_problem_id_and_number", unique: true, using: :btree
-  add_index "submissions", ["user_id", "problem_id"], name: "index_submissions_on_user_id_and_problem_id", using: :btree
-
-  create_table "tags", force: :cascade do |t|
-    t.string   "name",        limit: 255,   null: false
-    t.text     "description", limit: 65535
-    t.boolean  "public"
-    t.datetime "created_at",                null: false
-    t.datetime "updated_at",                null: false
+  create_table "tags", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
+    t.string "name", null: false
+    t.text "description"
+    t.boolean "public"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
   end
 
-  create_table "tasks", force: :cascade do |t|
-    t.integer  "submission_id", limit: 4
+  create_table "tasks", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+    t.integer "submission_id"
     t.datetime "created_at"
-    t.integer  "status",        limit: 4
+    t.integer "status"
     t.datetime "updated_at"
+    t.index ["submission_id"], name: "index_tasks_on_submission_id"
   end
 
-  add_index "tasks", ["submission_id"], name: "index_tasks_on_submission_id", using: :btree
-
-  create_table "test_pairs", force: :cascade do |t|
-    t.integer  "problem_id", limit: 4
-    t.text     "input",      limit: 16777215
-    t.text     "solution",   limit: 16777215
-    t.datetime "created_at"
-    t.datetime "updated_at"
+  create_table "test_pairs", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+    t.integer "problem_id"
+    t.text "input", limit: 4294967295
+    t.text "solution", limit: 4294967295
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
   end
 
-  create_table "test_requests", force: :cascade do |t|
-    t.integer  "user_id",          limit: 4
-    t.integer  "problem_id",       limit: 4
-    t.integer  "submission_id",    limit: 4
-    t.string   "input_file_name",  limit: 255
-    t.string   "output_file_name", limit: 255
-    t.string   "running_stat",     limit: 255
-    t.integer  "status",           limit: 4
-    t.datetime "updated_at"
+  create_table "test_requests", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+    t.integer "user_id"
+    t.integer "problem_id"
+    t.integer "submission_id"
+    t.string "input_file_name"
+    t.string "output_file_name"
+    t.string "running_stat"
+    t.integer "status"
+    t.datetime "updated_at", null: false
     t.datetime "submitted_at"
     t.datetime "compiled_at"
-    t.text     "compiler_message", limit: 65535
+    t.text "compiler_message", limit: 16777215
     t.datetime "graded_at"
-    t.string   "grader_comment",   limit: 255
-    t.datetime "created_at"
-    t.float    "running_time",     limit: 24
-    t.string   "exit_status",      limit: 255
-    t.integer  "memory_usage",     limit: 4
+    t.string "grader_comment"
+    t.datetime "created_at", null: false
+    t.float "running_time"
+    t.string "exit_status"
+    t.integer "memory_usage"
+    t.index ["user_id", "problem_id"], name: "index_test_requests_on_user_id_and_problem_id"
   end
 
-  add_index "test_requests", ["user_id", "problem_id"], name: "index_test_requests_on_user_id_and_problem_id", using: :btree
-
-  create_table "testcases", force: :cascade do |t|
-    t.integer  "problem_id", limit: 4
-    t.integer  "num",        limit: 4
-    t.integer  "group",      limit: 4
-    t.integer  "score",      limit: 4
-    t.text     "input",      limit: 4294967295
-    t.text     "sol",        limit: 4294967295
-    t.datetime "created_at"
-    t.datetime "updated_at"
+  create_table "testcases", id: :integer, options: "ENGINE=InnoDB DEFAULT 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.index ["problem_id"], name: "index_testcases_on_problem_id"
   end
 
-  add_index "testcases", ["problem_id"], name: "index_testcases_on_problem_id", using: :btree
-
-  create_table "user_contest_stats", force: :cascade do |t|
-    t.integer  "user_id",       limit: 4
+  create_table "user_contest_stats", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+    t.integer "user_id"
     t.datetime "started_at"
-    t.datetime "created_at"
-    t.datetime "updated_at"
-    t.boolean  "forced_logout"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.boolean "forced_logout"
   end
 
-  create_table "users", force: :cascade do |t|
-    t.string   "login",           limit: 50
-    t.string   "full_name",       limit: 255
-    t.string   "hashed_password", limit: 255
-    t.string   "salt",            limit: 5
-    t.string   "alias",           limit: 255
-    t.string   "email",           limit: 255
-    t.integer  "site_id",         limit: 4
-    t.integer  "country_id",      limit: 4
-    t.boolean  "activated",                   default: false
+  create_table "users", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+    t.string "login", limit: 50
+    t.string "full_name"
+    t.string "hashed_password"
+    t.string "salt", limit: 5
+    t.string "alias"
+    t.string "email"
+    t.integer "site_id"
+    t.integer "country_id"
+    t.boolean "activated", default: false
     t.datetime "created_at"
     t.datetime "updated_at"
-    t.string   "section",         limit: 255
-    t.boolean  "enabled",                     default: true
-    t.string   "remark",          limit: 255
-    t.string   "last_ip",         limit: 255
+    t.string "section"
+    t.boolean "enabled", default: true
+    t.string "remark"
+    t.string "last_ip"
+    t.index ["login"], name: "index_users_on_login", unique: true
   end
 
-  add_index "users", ["login"], name: "index_users_on_login", unique: true, using: :btree
-
   add_foreign_key "problems_tags", "problems"
   add_foreign_key "problems_tags", "tags"
 end