diff --git a/Gemfile b/Gemfile
--- a/Gemfile
+++ b/Gemfile
@@ -50,7 +50,7 @@
 # jquery addition
 gem 'jquery-rails'
 gem 'jquery-ui-rails'
-gem 'jquery-timepicker-addon-rails'
+#gem 'jquery-timepicker-addon-rails'
 gem 'jquery-tablesorter'
 gem 'jquery-countdown-rails'
 
@@ -62,10 +62,10 @@
 gem 'bootstrap-switch-rails'
 gem 'bootstrap-toggle-rails'
 gem 'autoprefixer-rails'
-gem 'momentjs-rails'
+gem 'momentjs-rails', '>= 2.9.0'
 gem 'rails_bootstrap_sortable'
-gem 'bootstrap-datepicker-rails'
-gem 'bootstrap3-datetimepicker-rails'
+#gem 'bootstrap-datepicker-rails'
+gem 'bootstrap3-datetimepicker-rails', '~> 4.17.47'
 #gem 'jquery-datatables-rails'
 
 #----------- user interface -----------------
@@ -75,7 +75,7 @@
 #ace editor
 gem 'ace-rails-ap'
 #paginator
-gem 'will_paginate', '~> 3.0.7'
+#gem 'will_paginate', '~> 3.0.7'
 
 gem 'mail'
 gem 'rdiscount'
diff --git a/Gemfile.lock b/Gemfile.lock
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -64,8 +64,6 @@
     bindex (0.8.1)
     bootsnap (1.4.6)
       msgpack (~> 1.0)
-    bootstrap-datepicker-rails (1.8.0.1)
-      railties (>= 3.0)
     bootstrap-sass (3.4.1)
       autoprefixer-rails (>= 5.2.1)
       sassc (>= 2.0.0)
@@ -122,11 +120,6 @@
     jbuilder (2.10.0)
       activesupport (>= 5.0.0)
     jquery-countdown-rails (2.0.2)
-    jquery-datatables-rails (3.4.0)
-      actionpack (>= 3.1)
-      jquery-rails
-      railties (>= 3.1)
-      sass-rails
     jquery-rails (4.3.3)
       rails-dom-testing (>= 1, < 3)
       railties (>= 4.2.0)
@@ -214,17 +207,6 @@
     ruby_parser (3.13.1)
       sexp_processor (~> 4.9)
     rubyzip (1.3.0)
-    sass (3.7.4)
-      sass-listen (~> 4.0.0)
-    sass-listen (4.0.0)
-      rb-fsevent (~> 0.9, >= 0.9.4)
-      rb-inotify (~> 0.9, >= 0.9.7)
-    sass-rails (5.0.7)
-      railties (>= 4.0.0, < 6)
-      sass (~> 3.1)
-      sprockets (>= 2.8, < 4.0)
-      sprockets-rails (>= 2.0, < 4.0)
-      tilt (>= 1.1, < 3)
     sassc (2.2.1)
       ffi (~> 1.9)
     sassc-rails (2.1.2)
@@ -272,7 +254,6 @@
     websocket-driver (0.7.1)
       websocket-extensions (>= 0.1.0)
     websocket-extensions (0.1.4)
-    will_paginate (3.0.12)
     xpath (3.2.0)
       nokogiri (~> 1.8)
     yaml_db (0.7.0)
@@ -288,11 +269,10 @@
   autoprefixer-rails
   best_in_place (~> 3.0.1)
   bootsnap (>= 1.1.0)
-  bootstrap-datepicker-rails
   bootstrap-sass (~> 3.4.1)
   bootstrap-switch-rails
   bootstrap-toggle-rails
-  bootstrap3-datetimepicker-rails
+  bootstrap3-datetimepicker-rails (~> 4.17.47)
   byebug
   capybara (>= 2.15)
   coffee-rails
@@ -303,7 +283,6 @@
   in_place_editing
   jbuilder (~> 2.5)
   jquery-countdown-rails
-  jquery-datatables-rails
   jquery-rails
   jquery-tablesorter
   jquery-timepicker-addon-rails
@@ -311,7 +290,7 @@
   listen (>= 3.0.5, < 3.2)
   mail
   minitest-reporters
-  momentjs-rails
+  momentjs-rails (>= 2.9.0)
   mysql2
   puma
   rails (~> 5.2)
@@ -329,8 +308,7 @@
   uglifier
   web-console (>= 3.3.0)
   webdriver
-  will_paginate (~> 3.0.7)
   yaml_db
 
 BUNDLED WITH
-   1.16.2
+   1.17.2
diff --git a/app/assets/javascripts/application.js b/app/assets/javascripts/application.js
--- a/app/assets/javascripts/application.js
+++ b/app/assets/javascripts/application.js
@@ -44,7 +44,7 @@
 //= require best_in_place
 //= require best_in_place.jquery-ui
 //= require brython
-//= require bootstrap-datepicker
+//= re quire bootstrap-datepicker
 //= require bootstrap-datetimepicker
 
 // since this is after blank line, it is not downloaded
diff --git a/app/assets/javascripts/custom.js.coffee b/app/assets/javascripts/custom.js.coffee
--- a/app/assets/javascripts/custom.js.coffee
+++ b/app/assets/javascripts/custom.js.coffee
@@ -12,7 +12,8 @@
 # document ready
 
 $ ->
-  $(".select2").select2()
+  $(".select2").select2({
+  })
   #$(".bootstrap-switch").bootstrapSwitch()
   #$(".bootstrap-toggle").bootstrapToggle()
   $('.btn-file :file').on 'fileselect', (event, numFiles, label) ->
diff --git a/app/assets/stylesheets/application.css.scss b/app/assets/stylesheets/application.css.scss
--- a/app/assets/stylesheets/application.css.scss
+++ b/app/assets/stylesheets/application.css.scss
@@ -19,8 +19,8 @@
 //@import "jquery.ui.theme";
 //@import "jquery.ui.datepicker";
 //@import "jquery.ui.slider";
-@import "jquery-ui-timepicker-addon";
-@import "jquery-tablesorter/theme.metro-dark";
+//@import "jquery-ui-timepicker-addon";
+//@import "jquery-tablesorter/theme.metro-dark";
 @import "jquery.countdown";
 @import "tablesorter-theme.cafe";
 
@@ -33,7 +33,7 @@
 //@import bootstrap3-switch
 @import "bootstrap-toggle";
 @import "bootstrap-sortable";
-@import "bootstrap-datepicker3";
+//@import "bootstrap-datepicker3";
 @import "bootstrap-datetimepicker";
 @import "datatables.net-bs/css/dataTables.bootstrap.min";
 @import "datatables.net-buttons-bs/css/buttons.bootstrap.min";
diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -167,12 +167,13 @@
   #function for datatable ajax query
   #return record,total_count,filter_count
   def process_query_record(record, 
-                           total_count: nil, 
-                           select: '', 
-                           global_search: [], 
-                           no_search: false, 
-                           force_order: '', 
-                           date_filter: '', date_param_since: 'date_since',date_param_until: 'date_until')
+                           total_count: nil,
+                           select: '',
+                           global_search: [],
+                           no_search: false,
+                           force_order: '',
+                           date_filter: '', date_param_since: 'date_since',date_param_until: 'date_until',
+                           hard_limit: nil)
     arel_table = record.model.arel_table
 
     if !no_search && params['search']
@@ -192,9 +193,11 @@
     end
 
     if !date_filter.blank?
-      date_since = Time.parse( params[:date_since] ) rescue Time.new(1,1,1)
-      date_until = Time.parse( params[:date_until] ) rescue Time.zone.now()
-      date_range = date_since..date_until
+      param_since = params[date_param_since]
+      param_until = params[date_param_until]
+      date_since = Time.zone.parse( param_since ) || Time.new(1,1,1) rescue Time.new(1,1,1)
+      date_until = Time.zone.parse( param_until ) || Time.zone.now() rescue Time.zone.now()
+      date_range = date_since..(date_until.end_of_day)
       record = record.where(date_filter.to_sym => date_range)
     end
 
@@ -217,7 +220,14 @@
       filterCount = filterCount.count
     end
 
-    record = record.offset(params['start'] || 0).limit(params['length'] || 100)
+
+    record = record.offset(params['start'] || 0)
+    record = record.limit(hard_limit)
+    if (params['length'])
+      limit = params['length'].to_i
+      limit == hard_limit if (hard_limit && hard_limit < limit)
+      record = record.limit(limit)
+    end
     if (!select.blank?)
       record = record.select(select)
     end
diff --git a/app/controllers/report_controller.rb b/app/controllers/report_controller.rb
--- a/app/controllers/report_controller.rb
+++ b/app/controllers/report_controller.rb
@@ -4,7 +4,7 @@
 
   before_action :check_valid_login
 
-  before_action :admin_authorization, only: [:login_stat,:submission_stat, :stuck, :cheat_report, :cheat_scruntinize, :show_max_score, :current_score]
+  before_action :admin_authorization, only: [:login_stat,:submission, :submission_query, :stuck, :cheat_report, :cheat_scruntinize, :show_max_score, :current_score]
 
   before_action(only: [:problem_hof]) { |c|
     return false unless check_valid_login
@@ -143,34 +143,33 @@
   end
 
   def submission
-    date_and_time = '%Y-%m-%d %H:%M'
-    begin
-      @since_time = DateTime.strptime(params[:since_datetime],date_and_time)
-    rescue
-      @since_time = DateTime.new(1000,1,1)
-    end
-    begin
-      @until_time = DateTime.strptime(params[:until_datetime],date_and_time)
-    rescue
-      @until_time = DateTime.new(3000,1,1)
-    end
-
-    @submissions = Submission
-      .joins(:problem).joins(:user)
   end
 
   def submission_query
     @submissions = Submission
-      .joins(:problem).joins(:user)
+      .includes(:problem).includes(:user).includes(:language)
+
+    if params[:problem]
+      @submission = @submission.where(problem_id: params[:problem])
+    end
+
+    case params[:users]
+    when 'enabled'
+      @submissions = @submissions.where('user.enabled': true)
+    when 'group'
+      @submissions = @submissions.joins(user: :groups).where(user: {groups: {id: params[:groups]}}) if params[:groups]
+    end
+
+    #set default
+    params[:since_datetime] = Date.today.to_s if params[:since_datetime].blank?
 
     @submissions, @recordsTotal, @recordsFiltered = process_query_record( @submissions,
       global_search: ['user.login','user.full_name','problem.name','problem.full_name','points'],
       date_filter: 'submitted_at',
       date_param_since: 'since_datetime',
       date_param_until: 'until_datetime',
+      hard_limit: 100_000
     )
-    puts '-------------------------------'
-    puts @submissions
   end
 
   def problem_hof
diff --git a/app/views/layouts/_header.html.haml b/app/views/layouts/_header.html.haml
--- a/app/views/layouts/_header.html.haml
+++ b/app/views/layouts/_header.html.haml
@@ -64,7 +64,7 @@
               %ul.dropdown-menu
                 = add_menu( 'Current Score', 'report', 'current_score')
                 = add_menu( 'Score Report', 'report', 'max_score')
-                = add_menu( 'Report', 'report', 'multiple_login')
+                = add_menu( 'Submission Report', 'report', 'submission')
             - if (ungraded = Submission.where('graded_at is null').where('submitted_at < ?', 1.minutes.ago).count) > 0
               =link_to "#{ungraded} backlogs!",
                 grader_list_path,
diff --git a/app/views/report/submission.html.haml b/app/views/report/submission.html.haml
--- a/app/views/report/submission.html.haml
+++ b/app/views/report/submission.html.haml
@@ -7,61 +7,71 @@
   .col-md-4
     = render partial: 'shared/problem_select'
   .col-md-4
-    = render partial: 'shared/problem_select'
+    = render partial: 'shared/date_filter'
   .col-md-4
     = render partial: 'shared/user_select'
 
+.row
+  .col-md-6
+    .alert.alert-info
+      %ul
+        %li Display a maximum of 100,000 entries to save computation power
+        %li You have to click refresh when changing the filter above
 
 .row
-  .col-12
-    %table.table.table-hover.table-condense.datatable
-      -#
-        %thead
-          %tr
-            %th User
-            %th Problem
-            %th Subbmission ID
-            %th Submit Time
-            %th Score
-            %th detail
-        %tbody
-          - @submissions.each do |s|
-            %tr
-              %td= s.user.login
-              %td= s.problem.long_name
-              %td= s.id
-              %td= s.submitted_at
-              %td= s.points
-              %td= s.grader_comment
+  .col-sm-12
+    %table.table.table-hover.table-condense.datatable{style: 'width: 100%'}
 
 
 :javascript
-  $('.datatable').DataTable({
-    dom: 'Bfrtip',
-    buttons: [
-        'copy', 'excel', 'pdf'
-    ],
-    columns: [
-      {title: 'Sub ID', data: 'id'},
-      {title: 'User', data: 'user.login'},
-      {title: 'Problem', data: 'problem.long_name'},
-      {title: 'Language', data: 'language.pretty_name'},
-      {title: 'Submit at', data: 'submitted_at'},
-      {title: 'Result', data: 'grader_comment'},
-      {title: 'Score', data: 'points'},
-      {title: 'IP', data: 'ip_address'},
-    ],
-    ajax: {
-      url: '#{submission_query_report_path}',
-      type: 'POST',
-      data: (d) =>  {
-        d.since_datetime = '1123'
-        d.until_datetime = 'xxx'
-      },
-      dataType: 'json',
-      beforeSend: (request) => {
-        request.setRequestHeader('X-CSRF-Token', $('meta[name="csrf-token"]').attr('content'));
-      },
-    }, //end ajax
-    'pageLength': 50
+  $(function() {
+    submission_table = $('.datatable').DataTable({
+      dom: "<'row'<'col-sm-3'B><'col-sm-3'l><'col-sm-6'f>>" + "<'row'<'col-sm-12'tr>>" + "<'row'<'col-sm-5'i><'col-sm-7'p>>",
+      autoWidth: true,
+      buttons: [
+        {
+          text: 'Refresh',
+          action: (e,dt,node,config) => {
+            submission_table.clear().draw()
+            submission_table.ajax.reload( () => { submission_table.columns.adjust().draw() } )
+          }
+        },
+        'copy', 'excel'
+      ],
+      columns: [
+        {title: 'Sub ID', data: 'id'},
+        {title: 'User', data: 'user.login'},
+        {title: 'Problem', data: 'problem.long_name'},
+        {title: 'Language', data: 'language.pretty_name'},
+        {title: 'Submit at', data: 'submitted_at'},
+        {title: 'Result', data: 'grader_comment'},
+        {title: 'Score', data: 'points'},
+        {title: 'IP', data: 'ip_address'},
+      ],
+      ajax: {
+        url: '#{submission_query_report_path}',
+        type: 'POST',
+        data: (d) =>  {
+          d.since_datetime = $('#since_datetime').val()
+          d.until_datetime = $('#until_datetime').val()
+          d.users = $("input[name='users']:checked").val()
+          d.problems = $("#problem_id").select2('val')
+          d.groups = $("#group_id").select2('val')
+        },
+        dataType: 'json',
+        beforeSend: (request) => {
+          request.setRequestHeader('X-CSRF-Token', $('meta[name="csrf-token"]').attr('content'));
+        },
+      }, //end ajax
+      'pageLength': 50,
+      processing: true,
+    });
+
+    $('.input-group.date').datetimepicker({
+      format: 'YYYY-MM-DD',
+      showTodayButton: true,
+      locale: 'en',
+      widgetPositioning: {horizontal: 'auto', vertical: 'bottom'},
+      defaultDate: moment()
+    });
   });
diff --git a/app/views/report/submission_query.json.jbuilder b/app/views/report/submission_query.json.jbuilder
--- a/app/views/report/submission_query.json.jbuilder
+++ b/app/views/report/submission_query.json.jbuilder
@@ -3,13 +3,15 @@
 json.recordsFiltered @recordsFiltered
 json.data do
   json.array! @submissions do |sub|
-    json.extract! sub, :id, :points, :grader_comment, :ip_address
-    json.submitted_at sub.submitted_at.to_s(:db)
+    json.extract! sub, :grader_comment, :ip_address
+    json.id "<a href='#{submission_path(sub)}'>#{sub.id}</a>"
+    json.submitted_at sub.submitted_at.strftime('%Y-%m-%d %H:%M')
+    json.points "#{sub.points}/#{sub.problem&.full_score}"
     json.problem do
-      json.long_name sub.problem&.long_name
+      json.long_name sub.problem ? sub.problem.long_name : '-- deleted problem --'
     end
     json.user do
-      json.login sub.user&.login
+      json.login sub.user ? "<a href='#{stat_user_path(sub.user)}'>(#{sub.user&.login})</a> #{sub.user&.full_name}" : '-- deleted user --'
     end
     json.language do
       json.pretty_name sub.language&.pretty_name
diff --git a/app/views/shared/_date_filter.html.haml b/app/views/shared/_date_filter.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/shared/_date_filter.html.haml
@@ -0,0 +1,20 @@
+.panel.panel-primary
+  .panel-heading
+    Date ranges
+  .panel-body
+    .row.form-group
+      .col-md-4
+        From Date:
+      .col-md-6
+        .input-group.date
+          = text_field_tag :since_datetime, nil, class: 'form-control'
+          %span.input-group-addon
+            %span.glyphicon.glyphicon-calendar
+    .row.form-group
+      .col-md-4
+        Until Date:
+      .col-md-6
+        .input-group.date
+          = text_field_tag :until_datetime, nil, class: 'form-control'
+          %span.input-group-addon
+            %span.glyphicon.glyphicon-calendar
diff --git a/app/views/shared/_problem_select.html.haml b/app/views/shared/_problem_select.html.haml
--- a/app/views/shared/_problem_select.html.haml
+++ b/app/views/shared/_problem_select.html.haml
@@ -3,8 +3,8 @@
     Problems
   .panel-body
     %p
-      Select problem(s) that we wish to know the score.
+      Select problem(s) to be included in the report
     = label_tag :problem_id, "Problems"
     = select_tag 'problem_id[]',
         options_for_select(Problem.all.collect {|p| ["[#{p.name}] #{p.full_name}", p.id]},params[:problem_id]),
-        { class: 'select2 form-control', multiple: "true" }
+        { id: :problem_id, class: 'select2 form-control', multiple: "true" }
diff --git a/app/views/shared/_user_select.html.haml b/app/views/shared/_user_select.html.haml
--- a/app/views/shared/_user_select.html.haml
+++ b/app/views/shared/_user_select.html.haml
@@ -10,3 +10,10 @@
       %label
         = radio_button_tag 'users', 'enabled', (params[:users] == "enabled")
         Only enabled users
+    .radio
+      %label
+        = radio_button_tag 'users', 'group', (params[:users] == "group")
+        Only these groups
+    = select_tag 'group_id[]',
+        options_for_select(Group.all.collect {|g| ["[#{g.name}] #{g.description}", g.id]}),
+        { id: 'group_id', class: 'select2 form-control', multiple: "true"}
diff --git a/db/migrate/20200404135714_add_index_to_submission.rb b/db/migrate/20200404135714_add_index_to_submission.rb
new file mode 100644
--- /dev/null
+++ b/db/migrate/20200404135714_add_index_to_submission.rb
@@ -0,0 +1,5 @@
+class AddIndexToSubmission < ActiveRecord::Migration[5.2]
+  def change
+    add_index :submissions, :submitted_at
+  end
+end
diff --git a/db/migrate/20200404142959_add_id_to_group_user.rb b/db/migrate/20200404142959_add_id_to_group_user.rb
new file mode 100644
--- /dev/null
+++ b/db/migrate/20200404142959_add_id_to_group_user.rb
@@ -0,0 +1,5 @@
+class AddIdToGroupUser < ActiveRecord::Migration[5.2]
+  def change
+    add_column :groups_users, :id, :primary_key
+  end
+end
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