Delete from Database with Specific Details in Ruby

Delete from database with specific details in ruby

From the comments, I learned that you are running a very old version of Ruby on Rails – probably more than 10 years old. With Rails 3.0 the finder methods change completely and therefore all current documentation for Rails will not be helpful anymore. Especially the where method did not exist before Rails 3.0

In such an old version the following should work:

YourModel.destroy_all("id in (?)", @recipient.split(','))

Here you will find the docs of older Rails versions.

The condition is basically just one SQL fragment. When you want to add more conditions then you need to write all conditions in one line like this:

YourModel.destroy_all(
  "id IN (?) AND thread = ?", @recipient.split(','), @dis_PI.m_id
)

Deleting all records in a database table

If you are looking for a way to it without SQL you should be able to use delete_all.

Post.delete_all

or with a criteria

Post.delete_all "person_id = 5 AND (category = 'Something' OR category = 'Else')"

See here for more information.

The records are deleted without loading them first which makes it very fast but will break functionality like counter cache that depends on rails code to be executed upon deletion.

Deleting a record from database

@variable.destroy will call all callbacks (before_destroy etc.) as well as ensure associations are respected. @variable.delete just calls the raw database query to delete the object. You're generally much safer off using destroy even if it's more expensive.

Only delete from memory not from database

Beware if you are using has_many relationship the answer by JP will not work.

Extending the example:

class City < ActiveRecord::Base
  has_many :shops
end

city = City.find(:name => "Portland")

then

city.shops.delete(city.shops[0])

Will delete from the DB!

Also

theshops = city.shops
theshops.delete(ss[0])

Will delete from the DB

One way to detach from the DB is to use compact or another array function like so:

theshops = city.shops.compact
theshops.delete(ss[0])

Will not delete from the DB

Also, in all cases delete_if Will not delete from the db:

city.shops.delete_if {|s| s.id == city.shops[0]}

Cheers!

Don't forget: If you are in doubt about these sort of things script/console is your friend!

how to automatically delete a record from the database in rails

There are different ways on how to handle this task. Check 2 options below.

Option 1 - whenever gem

You would setup a task using whenever which runs for example every 30 days.

1- Generate task as following:

rails g task posts delete_30_days_old

2- Create a ruby file in your application

# lib/tasks/delete_old_records.rb
namespace :posts do
  desc "Delete records older than 30 days"
  task delete_30_days_old: :environment do
    Post.where(['created_at < ?', 30.days.ago]).destroy_all
  end
end

Option 2 - sidekick and Sidetiq gems

# in app/workers/clean_posts.rb
class CleanPosts
  include Sidekiq::Worker
  include Sidetiq::Schedulable

  recurrence { monthly }

  def perform
    Post.recent.destroy_all
  end
end

and

# /models/post.rb
class Post < ApplicationRecord
  scope :recent, -> { where('created_at >= :thirty_days_ago', thiryty_days_ago: Time.now - 30.days) }
end

Since Ruby is about beauty, move the where clause to your model, where can reuse it.

These options will remove old posts from your DB and they will no longer be accessible by your application.

How do you delete an ActiveRecord object?

It's destroy and destroy_all methods, like

user.destroy
User.find(15).destroy
User.destroy(15)
User.where(age: 20).destroy_all
User.destroy_all(age: 20)

Alternatively you can use delete and delete_all which won't enforce :before_destroy and :after_destroy callbacks or any dependent association options.

User.delete_all(condition: 'value') will allow you to delete records
without a primary key

Note: from @hammady's comment, user.destroy won't work if User model has no primary key.

Note 2: From @pavel-chuchuva's comment, destroy_all with conditions and delete_all with conditions has been deprecated in Rails 5.1 - see guides.rubyonrails.org/5_1_release_notes.html

Rails - Delete all Records that Meet a Condition

I think it is better to use destroy instead of delete

because destroy will delete current object record from db and also its
associated children record from db (https://stackoverflow.com/a/22757656/5452072)

Also delete will skip callbacks, but destroy doesn't.

Manager.where(:manager_level => 5).destroy_all

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