ajax datatables rails

A wrapper around DataTable's ajax methods that allow synchronization with server-side pagination in a Rails app

jbox-web

591

227

Ruby

ajax-datatables-rails

Important : This gem is targeted at DataTables version 1.10.x.

It’s tested against :

Rails: 7.0.4 / 7.1.0 / 7.2.0
Ruby: 3.0 / 3.1 / 3.2 / 3.3
Databases: MySQL 8 / SQLite3 / Postgresql 16 / Oracle XE 11.2 (thanks to travis-oracle)
Adapters: sqlite / mysql2 / trilogy / postgres / postgis / oracle

Description

DataTables is a nifty jQuery plugin that adds the ability to paginate, sort, and search your html tables.
When dealing with large tables (more than a couple of hundred rows) however, we run into performance issues.
These can be fixed by using server-side pagination, but this breaks some DataTables functionality.

ajax-datatables-rails is a wrapper around DataTables ajax methods that allow synchronization with server-side pagination in a Rails app.
It was inspired by this Railscast.
I needed to implement a similar solution in a couple projects I was working on, so I extracted a solution into a gem.

Joel Quenneville (original author)

I needed a good gem to manage a lot of DataTables so I chose this one 😃

Nicolas Rodriguez (current maintainer)

The final goal of this gem is to generate a JSON content that will be given to jQuery DataTables.
All the datatable customizations (header, tr, td, css classes, width, height, buttons, etc…) must take place in the javascript definition of the datatable.
jQuery DataTables is a very powerful tool with a lot of customizations available. Take the time to read the doc.

You’ll find a sample project here : https://ajax-datatables-rails.herokuapp.com

Its real world examples. The code is here : https://github.com/jbox-web/ajax-datatables-rails-sample-project

Installation

Add these lines to your application’s Gemfile:

gem 'ajax-datatables-rails'

And then execute:

$ bundle install

We assume here that you have already installed jQuery DataTables.

You can install jQuery DataTables :

with the jquery-datatables gem
by adding the assets manually (in vendor/assets)
with Rails webpacker gem (see here for more infos)

Note

Currently AjaxDatatablesRails only supports ActiveRecord as ORM for performing database queries.

Adding support for Sequel, Mongoid and MongoMapper is (more or less) a planned feature for this gem.

If you’d be interested in contributing to speed development, please open an issue and get in touch.

Quick start (in 5 steps)

The following examples assume that we are setting up ajax-datatables-rails for an index page of users from a User model,
and that we are using Postgresql as our db, because you should be using it. (It also works with other DB, see above)

The goal is to render a users table and display : id, first name, last name, email, and bio for each user.

Something like this:

ID	First Name	Last Name	Email	Brief Bio
1	John	Doe	[email protected]	Is your default user everywhere
2	Jane	Doe	[email protected]	Is John’s wife
3	James	Doe	[email protected]	Is John’s brother and best friend

Here the steps we’re going through :

Generate the datatable class
Build the View
Customize the generated Datatables class
Setup the Controller action
Wire up the Javascript

1) Generate the datatable class

Run the following command:

$ rails generate datatable User

This will generate a file named user_datatable.rb in app/datatables.
Open the file and customize in the functions as directed by the comments.

Take a look here for an explanation about the generator syntax.

2) Build the View

You should always start by the single source of truth, which is your html view.

Set up an html <table> with a <thead> and <tbody>
Add in your table headers if desired
Don’t add any rows to the body of the table, DataTables does this automatically
Add a data attribute to the <table> tag with the url of the JSON feed, in our case is the users_path as we’re pointing to the UsersController#index action

<table id="users-datatable" data-source="<%= users_path(format: :json) %>">
  <thead>
    <tr>
      <th>ID</th>
      <th>First Name</th>
      <th>Last Name</th>
      <th>Email</th>
      <th>Brief Bio</th>
    </tr>
  </thead>
  <tbody>
  </tbody>
</table>

3) Customize the generated Datatables class

a. Declare columns mapping

First we need to declare in view_columns the list of the model(s) columns mapped to the data we need to present.
In this case: id, first_name, last_name, email and bio.

This gives us:

def view_columns
  @view_columns ||= {
    id:         { source: "User.id" },
    first_name: { source: "User.first_name", cond: :like, searchable: true, orderable: true },
    last_name:  { source: "User.last_name",  cond: :like, nulls_last: true },
    email:      { source: "User.email" },
    bio:        { source: "User.bio" },
  }
end

Notes : by default orderable and searchable are true and cond is :like.

cond can be :

:like, :start_with, :end_with, :string_eq, :string_in for string or full text search
:eq, :not_eq, :lt, :gt, :lteq, :gteq, :in for numeric
:date_range for date range
:null_value for nil field
Proc for whatever (see here for real example)

The nulls_last param allows for nulls to be ordered last. You can configure it by column, like above, or by datatable class :

class MyDatatable < AjaxDatatablesRails::ActiveRecord
  self.nulls_last = true

  # ... other methods (view_columns, data...)
end

See here to get more details about columns definitions and how to play with associated models.

You can customize or sanitize the search value passed to the DB by using the :formatter option with a lambda :

def view_columns
  @view_columns ||= {
    id:         { source: "User.id" },
    first_name: { source: "User.first_name" },
    last_name:  { source: "User.last_name" },
    email:      { source: "User.email", formatter: -> (o) { o.upcase } },
    bio:        { source: "User.bio" },
  }
end

The object passed to the lambda is the search value.

b. Map data

Then we need to map the records retrieved by the get_raw_records method to the real values we want to display :

def data
  records.map do |record|
    {
      id:         record.id,
      first_name: record.first_name,
      last_name:  record.last_name,
      email:      record.email,
      bio:        record.bio,
      DT_RowId:   record.id, # This will automagically set the id attribute on the corresponding <tr> in the datatable
    }
  end
end

Deprecated: You can either use the v0.3 Array style for your columns :

This method builds a 2d array that is used by datatables to construct the html
table. Insert the values you want on each column.

def data
  records.map do |record|
    [
      record.id,
      record.first_name,
      record.last_name,
      record.email,
      record.bio
    ]
  end
end

The drawback of this method is that you can’t pass the DT_RowId so it’s tricky to set the id attribute on the corresponding <tr> in the datatable (need to be done on JS side).

See here if you need to use view helpers like link_to, mail_to, etc…

c. Get Raw Records

This is where your query goes.

def get_raw_records
  User.all
end

Obviously, you can construct your query as required for the use case the datatable is used.

Example:

def get_raw_records
  User.active.with_recent_messages
end

You can put any logic in get_raw_records based on any parameters you inject in the Datatable object.

IMPORTANT : Because the result of this method will be chained to ActiveRecord methods for sorting, filtering and pagination,
make sure to return an ActiveRecord::Relation object.

d. Additional data

You can inject other key/value pairs in the rendered JSON by defining the #additional_data method :

def additional_data
  {
    foo: 'bar'
  }
end

Very useful with datatables-factory (or yadcf) to provide values for dropdown filters.

4) Setup the Controller action

Set the controller to respond to JSON

def index
  respond_to do |format|
    format.html
    format.json { render json: UserDatatable.new(params) }
  end
end

Don’t forget to make sure the proper route has been added to config/routes.rb.

See here if you need to inject params in the UserDatatable.

Note : If you have more than 2 datatables in your application, don’t forget to read this.

5) Wire up the Javascript

Finally, the javascript to tie this all together. In the appropriate coffee file:

# users.coffee

$ ->
  $('#users-datatable').dataTable
    processing: true
    serverSide: true
    ajax:
      url: $('#users-datatable').data('source')
    pagingType: 'full_numbers'
    columns: [
      {data: 'id'}
      {data: 'first_name'}
      {data: 'last_name'}
      {data: 'email'}
      {data: 'bio'}
    ]
    # pagingType is optional, if you want full pagination controls.
    # Check dataTables documentation to learn more about
    # available options.

or, if you’re using plain javascript:

// users.js

jQuery(document).ready(function() {
  $('#users-datatable').dataTable({
    "processing": true,
    "serverSide": true,
    "ajax": {
      "url": $('#users-datatable').data('source')
    },
    "pagingType": "full_numbers",
    "columns": [
      {"data": "id"},
      {"data": "first_name"},
      {"data": "last_name"},
      {"data": "email"},
      {"data": "bio"}
    ]
    // pagingType is optional, if you want full pagination controls.
    // Check dataTables documentation to learn more about
    // available options.
  });
});

Advanced usage

Using view helpers

Sometimes you’ll need to use view helper methods like link_to, mail_to,
edit_user_path, check_box_tag and so on in the returned JSON representation returned by the data method.

To have these methods available to be used, this is the way to go:

class UserDatatable < AjaxDatatablesRails::ActiveRecord
  extend Forwardable

  # either define them one-by-one
  def_delegator :@view, :check_box_tag
  def_delegator :@view, :link_to
  def_delegator :@view, :mail_to
  def_delegator :@view, :edit_user_path

  # or define them in one pass
  def_delegators :@view, :check_box_tag, :link_to, :mail_to, :edit_user_path

  # ... other methods (view_columns, get_raw_records...)

  def initialize(params, opts = {})
    @view = opts[:view_context]
    super
  end

  # now, you'll have these methods available to be used anywhere
  def data
    records.map do |record|
      {
        id:         check_box_tag('users[]', record.id),
        first_name: link_to(record.first_name, edit_user_path(record)),
        last_name:  record.last_name,
        email:      mail_to(record.email),
        bio:        record.bio
        DT_RowId:   record.id,
      }
    end
  end
end

# and in your controller:
def index
  respond_to do |format|
    format.html
    format.json { render json: UserDatatable.new(params, view_context: view_context) }
  end
end

Using view decorators

If you want to keep things tidy in the data mapping method, you could use
Draper to define column mappings like below.

Note : This is the recommanded way as you don’t need to inject the view_context in the Datatable object to access helpers methods.
It also helps in separating view/presentation logic from filtering logic (the only one that really matters in a datatable class).

Example :

class UserDatatable < AjaxDatatablesRails::ActiveRecord
  ...
  def data
    records.map do |record|
      {
        id:         record.decorate.check_box,
        first_name: record.decorate.link_to,
        last_name:  record.decorate.last_name
        email:      record.decorate.email,
        bio:        record.decorate.bio
        DT_RowId:   record.id,
      }
    end
  end
  ...
end

class UserDecorator < ApplicationDecorator
  delegate :last_name, :bio

  def check_box
    h.check_box_tag 'users[]', object.id
  end

  def link_to
    h.link_to object.first_name, h.edit_user_path(object)
  end

  def email
    h.mail_to object.email
  end

  # Just an example of a complex method you can add to you decorator
  # To render it in a datatable just add a column 'dt_actions' in
  # 'view_columns' and 'data' methods and call record.decorate.dt_actions
  def dt_actions
    links = []
    links << h.link_to 'Edit',   h.edit_user_path(object) if h.policy(object).update?
    links << h.link_to 'Delete', h.user_path(object), method: :delete, remote: true if h.policy(object).destroy?
    h.safe_join(links, '')
  end
end

Pass options to the datatable class

An AjaxDatatablesRails::ActiveRecord inherited class can accept an options hash at initialization. This provides room for flexibility when required.

Example:

# In the controller
def index
  respond_to do |format|
    format.html
    format.json { render json: UserDatatable.new(params, user: current_user, from: 1.month.ago) }
  end
end

# The datatable class
class UnrespondedMessagesDatatable < AjaxDatatablesRails::ActiveRecord

  # ... other methods (view_columns, data...)

  def user
    @user ||= options[:user]
  end

  def from
    @from ||= options[:from].beginning_of_day
  end

  def to
    @to ||= Date.today.end_of_day
  end

  # We can now customize the get_raw_records method
  # with the options we've injected
  def get_raw_records
    user.messages.unresponded.where(received_at: from..to)
  end

end

Change the DB adapter for a datatable class

If you have models from different databases you can set the db_adapter on the datatable class :

class MySharedModelDatatable < AjaxDatatablesRails::ActiveRecord
  self.db_adapter = :oracle_enhanced

  # ... other methods (view_columns, data...)

  def get_raw_records
    AnimalsRecord.connected_to(role: :reading) do
      Dog.all
    end
  end
end

Columns syntax

You can mix several model in the same datatable.

Suppose we have the following models: User, PurchaseOrder,
Purchase::LineItem and we need to have several columns from those models
available in our datatable to search and sort by.

# we use the ModelName.column_name notation to declare our columns

def view_columns
  @view_columns ||= {
    first_name:       { source: 'User.first_name' },
    last_name:        { source: 'User.last_name' },
    order_number:     { source: 'PurchaseOrder.number' },
    order_created_at: { source: 'PurchaseOrder.created_at' },
    quantity:         { source: 'Purchase::LineItem.quantity' },
    unit_price:       { source: 'Purchase::LineItem.unit_price' },
    item_total:       { source: 'Purchase::LineItem.item_total }'
  }
end

Associated and nested models

The previous example has only one single model. But what about if you have
some associated nested models and in a report you want to show fields from
these tables.

Take an example that has an Event, Course, CourseType, Allocation, Teacher, Contact, Competency and CompetencyType models. We want to have a datatables
report which has the following column:

'course_types.name'
'courses.name'
'contacts.full_name'
'competency_types.name'
'events.title'
'events.event_start'
'events.event_end'
'events.status'

We want to sort and search on all columns of the list.
The related definition would be :

def view_columns
  @view_columns ||= {
    course_type:     { source: 'CourseType.name' },
    course_name:     { source: 'Course.name' },
    contact_name:    { source: 'Contact.full_name' },
    competency_type: { source: 'CompetencyType.name' },
    event_title:     { source: 'Event.title' },
    event_start:     { source: 'Event.event_start' },
    event_end:       { source: 'Event.event_end' },
    event_status:    { source: 'Event.status' },
  }
end

def get_raw_records
  Event.joins(
    { course: :course_type },
    { allocations: {
      teacher: [:contact, { competencies: :competency_type }]
    }
  }).distinct
end

Some comments for the above code :

In the get_raw_records method we have quite a complex query having one to
many and many to many associations using the joins ActiveRecord method.
The joins will generate INNER JOIN relations in the SQL query. In this case,
we do not include all event in the report if we have events which is not
associated with any model record from the relation.
To have all event records in the list we should use the .includes method,
which generate LEFT OUTER JOIN relation of the SQL query.

IMPORTANT :

Make sure to append .references(:related_model) with any
associated model. That forces the eager loading of all the associated models
by one SQL query, and the search condition for any column works fine.
Otherwise the :recordsFiltered => filter_records(get_raw_records).count(:all)
will generate 2 SQL queries (one for the Event model, and then another for the
associated tables). The :recordsFiltered => filter_records(get_raw_records).count(:all)
will use only the first one to return from the ActiveRecord::Relation object
in get_raw_records and you will get an error message of Unknown column
‘yourtable.yourfield’ in ‘where clause’ in case the search field value
is not empty.

So the query using the .includes() method is:

def get_raw_records
  Event.includes(
    { course: :course_type },
    { allocations: {
      teacher: [:contact, { competencies: :competency_type }]
    }
  }).references(:course).distinct
end

Default scope

See DefaultScope is evil and #223 and #233.

DateRange search

This feature works with datatables-factory (or yadcf).

To enable the date range search, for example created_at :

add a created_at <th> in your html
declare your column in view_columns : created_at: { source: 'Post.created_at', cond: :date_range, delimiter: '-yadcf_delim-' }
add it in data : created_at: record.decorate.created_at
setup yadcf to make created_at search field a range

Generator Syntax

Also, a class that inherits from AjaxDatatablesRails::ActiveRecord is not tied to an
existing model, module, constant or any type of class in your Rails app.
You can pass a name to your datatable class like this:

$ rails generate datatable users
# returns a users_datatable.rb file with a UsersDatatable class

$ rails generate datatable contact_messages
# returns a contact_messages_datatable.rb file with a ContactMessagesDatatable class

$ rails generate datatable UnrespondedMessages
# returns an unresponded_messages_datatable.rb file with an UnrespondedMessagesDatatable class

In the end, it’s up to the developer which model(s), scope(s), relationship(s)
(or else) to employ inside the datatable class to retrieve records from the
database.

Tests

Datatables can be tested with Capybara provided you don’t use Webrick during integration tests.

Long story short and as a rule of thumb : use the same webserver everywhere (dev, prod, staging, test, etc…).

If you use Puma (the Rails default webserver), use Puma everywhere, even in CI/test environment. The same goes for Thin.

You will avoid the usual story : it works in dev but not in test environment…

If you want to test datatables with a lot of data you might need this kind of tricks : https://robots.thoughtbot.com/automatically-wait-for-ajax-with-capybara. (thanks CharlieIGG)

ProTips™

Create a master parent class (Easy)

In the same spirit of Rails ApplicationController and ApplicationRecord, you can create an ApplicationDatatable class (in app/datatables/application_datatable.rb)
that will be inherited from other classes :

class ApplicationDatatable < AjaxDatatablesRails::ActiveRecord
  # puts commonly used methods here
end

class PostDatatable < ApplicationDatatable
end

This way it will be easier to DRY you datatables.

Speedup JSON rendering (Easy)

Install yajl-ruby, basically :

gem 'yajl-ruby', require: 'yajl'

then

$ bundle install

That’s all 😃 (Automatically prefer Yajl or JSON backend over Yaml, if available)

Use HTTP `POST` method (Medium)

Use HTTP POST method to avoid 414 Request-URI Too Large error. See : #278 and #308.

You can easily define a route concern in config/routes.rb and reuse it when you need it :

Rails.application.routes.draw do
  concern :with_datatable do
    post 'datatable', on: :collection
  end

  resources :posts, concerns: [:with_datatable]
  resources :users, concerns: [:with_datatable]
end

then in your controllers :

# PostsController
  def index
  end

  def datatable
    render json: PostDatatable.new(params)
  end

# UsersController
  def index
  end

  def datatable
    render json: UserDatatable.new(params)
  end

then in your views :

# posts/index.html.erb
<table id="posts-datatable" data-source="<%= datatable_posts_path(format: :json) %>">

# users/index.html.erb
<table id="users-datatable" data-source="<%= datatable_users_path(format: :json) %>">

then in your Coffee/JS :

# send params in form data
$ ->
  $('#posts-datatable').dataTable
    ajax:
      url: $('#posts-datatable').data('source')
      type: 'POST'
    # ...others options, see [here](#5-wire-up-the-javascript)

# send params as json data
$ ->
  $('#users-datatable').dataTable
    ajax:
      url: $('#users-datatable').data('source')
      contentType: 'application/json'
      type: 'POST'
      data: (d) ->
        JSON.stringify d
    # ...others options, see [here](#5-wire-up-the-javascript)

Create indices for Postgresql (Expert)

In order to speed up the ILIKE queries that are executed when using the default configuration, you might want to consider adding some indices.
For postgresql, you are advised to use the gin/gist index type.
This makes it necessary to enable the postgrsql extension pg_trgm. Double check that you have this extension installed before trying to enable it.
A migration for enabling the extension and creating the indices could look like this:

def change
  enable_extension :pg_trgm
  TEXT_SEARCH_ATTRIBUTES = ['your', 'attributes']
  TABLE = 'your_table'

  TEXT_SEARCH_ATTRIBUTES.each do |attr|
    reversible do |dir|
      dir.up do
        execute "CREATE INDEX #{TABLE}_#{attr}_gin ON #{TABLE} USING gin(#{attr} gin_trgm_ops)"
      end

      dir.down do
        remove_index TABLE.to_sym, name: "#{TABLE}_#{attr}_gin"
      end
    end
  end
end

Tutorial

Filtering by JSONB column values : #277

Use has_scope gem with ajax-datatables-rails : #280

Use Datatable orthogonal data : see #269

Contributing

Fork it
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Added some feature')
Push to the branch (git push origin my-new-feature)
Create new Pull Request