No error on updating deleted object in rails-CodePudding

Rails executing update on deleted records.

I have a web app on ruby on rails in which I created some users and after that I opened the rails console and assigned U1 to one of my user let say last user then assigned the same User to U2. Then I run U1.destroy which executes successfully you can check screenshot after that I updated the name of user through U2 and it returns me true Although, user was destroyed from database when I checked it. My concern is rails should give me false as there was no object in database against that ID.

CodePudding user response：

If you want to double check that record exists before updating you can use reload

user.reload.update(name: "Some Name")

It will raise ActiveRecord::RecordNotFound if record with such id is absent

CodePudding user response：

UPDATE changes the values of the specified columns in all rows that satisfy the condition. https://www.postgresql.org/docs/current/sql-update.html

Rails doesn't return false or raise an exception because the UPDATE is still a valid query in the database, even if no rows match the condition. If you connect directly to your PostgreSQL database and run...

UPDATE users
SET name = 'test'
WHERE id = 123

...if 123 is an id that no longer exists, then the database will successfully execute the query and respond with:

UPDATE 0

If it is an id that still exists, the database will respond with:

UPDATE 1

This is similar to how Rails behaves if you use update_all. If you were to run update_all on a record that no longer exists, you'd see something like:

User.where(id: 123).update_all(name: 'test')
 => 0

But if the record exists you'd see:

User.where(id: 123).update_all(name: 'test')
 => 1

No error will be raised.

The purpose of the Rails update and update_all methods is just to attempt to run an UPDATE query in the database. If there is a timing issue and the record no longer exists, that's not something that the database or Rails is designed to give warnings about.