Minidusen: Filtering associated records

Minidusen lets you find text in associated records.

Assume the following model where a Contact record may be associated with a Group record:

class Contact < ApplicationRecord
  belongs_to :group

  validates_presence_of :name, :street, :city, :email
end

class Group < ApplicationRecord
  has_many :contacts

  validates_presence_of :name
end

We can filter contacts by their group name by joining the groups table and filtering on a joined column.
Note how the joined column is qualified as groups.name (rather than just name):

class ContactFilter
  include Minidusen::Filter

  filter :text do |scope, phrases|
    columns = [:name, :email, 'groups.name']
    scope.joins(:group).where_like(columns => phrases)
  end
end

github.com

Henning Koch

makandra.com

Say thanks

Last edit

Over 3 years ago

Jakob Scholz

License

Source code in this card is licensed under the MIT License.

FactoryBot: Passing attributes to associated records using transient attributes

FactoryBot.define do

  factory :parent do
    transient do
      child_name nil
      child_allowed_to_drive false
    end
    
    child do
      association(:child, name: child_name, allowed_to_drive: child_allowed_to_drive)
    end
  e...

Don't forget: Automatically remove join records on has_many :through associations

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# Given the following models

class Image < ActiveRecord::Base
  has_many :album_images
  has_many :albums, through: :album_images
end

class Album < ActiveRecord::Base
  has_many :album_images
  has_many :images, through: :album_i...

Use find_in_batches or find_each to deal with many records efficiently

Occasionally you need to do something directly on the server -- like having all records recalculate something that cannot be done in a migration because it takes a long time.

Let's say you do something like this:

Project.all.each(&:recal...

Rails: Composing an ETag from multiple records

Rails offers the fresh_when method to automatically compute an ETag from the given record, array of records or scope of records:

class UsersController < ApplicationController
  def show
    @user = User.find(params[:id])
    fresh_when ...

Retrieve the total number of records when paginating with will_paginate

When you use will_paginage to paginate a scope, and you want to obtain the total number of records matched before pagination, you can use total_entries:

users = User.active.paginate
puts users....

ActiveRecord: Creating many records works faster in a transaction

When you need to insert many records into the same table, performance may become an issue.

What you can do to save time is to open a transaction and save multiple records within that transaction:

transaction do
  500.times { Model.create!...

Validations on associated objects

Validations that need to access an associated object may lead to some trouble. Let's exemplify that using this example:

class Project < ActiveRecord::Base
   has_one :note
end

class Note < ActiveRecord::Base
   belongs_to :pr...

Posted by Henning Koch to makandra dev (2020-11-16 15:59)

Minidusen: Filtering associated records

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