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#3075 ✓resolved

Add :dependent => :restricted to has_one and has_many

Reported by CancelProfileIsBroken | August 19th, 2009 @ 02:26 PM | in 3.0.2

Based on , this patch adds a :dependent => :restricted option to has_one and has_many associations. This mirrors the common ON DELETE RESTRICT found in databases: if the parent has at least one child, do not allow the parent to be deleted. So, for example, trying to delete a customer with orders throws an error rather than deleting the orders or nullifying their foreign keys.

Patch builds on the original gist by:

  • Fixing up RDoc
  • Covering has_one as well as has_many
  • Adding tests

Tested on sqlite3, mysql, postgresql. Patch applies cleanly to master and 2-3-stable.

Comments and changes to this ticket

  • Jon Dahl

    Jon Dahl August 19th, 2009 @ 03:45 PM

    Big thanks for turning this into a "real" patch, Mike.

    Two small comments.

    First, the "else" path should be modified to list the :restrict option:

    raise ArgumentError, "The :dependent option expects either :destroy, :delete, :restrict, or :nullify (#{reflection.options[:dependent].inspect})"

    Second, is ActiveRecord::StatementInvalid the right exception to raise here? I threw that in to my sample code just because it's what would be raised by a DB foreign key that restricted deletes. But this isn't technically an invalid SQL statement. Is it worth creating a new exception class for this?

  • Pratik

    Pratik August 19th, 2009 @ 03:49 PM

    Yup we should have a new exception here.

  • Jon Dahl

    Jon Dahl August 19th, 2009 @ 04:14 PM

    I'll test the patch on an app today, and add a new exception - ActiveRecord::DependentRecordError or something like that.

  • CancelProfileIsBroken
  • Xavier Noria

    Xavier Noria August 21st, 2009 @ 06:40 PM

    Good, there are common use cases for this. Just some minor details:

    • The title of the ticket itself reads :restricted :-).

    • There are a couple of places where docs say "If the association is marked as :dependent => :restrict, create a callback that prevents deleting entirely.". That's true if there exists children, otherwise deletion is performed.

    • I think it could be good to document ActiveRecord::DeleteRestrictionError somewhere, because now destroy may throw it.

    • I'd prefer not to load the parent record in has_one to check if it exists, but there is no API for that it would need to be done by hand I guess. (Just a remark... no sure it is worth the trouble, I have in mind exists == @target || select 1 or something in that line).

    • There's also a case in HasOneAssociation#replace that I think should say something about :restrict. I don't really remember what's the purpose of #replace. The premise is that child records are untouchable, so an exception would make sense. You are not deleting the parent though, but you do not have information about how to destroy the child either. I think what to do is not completly clear, but I believe raising the exception is sound.

  • CancelProfileIsBroken

    CancelProfileIsBroken September 25th, 2009 @ 12:49 PM

    • Tag set to bugmash
    • Assigned user cleared.
  • Elad Meidar

    Elad Meidar September 26th, 2009 @ 07:52 AM

    +1 on idea but patch (v2) does not apply on neither master or 2-3-stable. i've attached a patch for both, please note that i had no idea how to credit mike for the entire thing, so my name is up there should be changed to mike before committing

    @xavier, your 4th point is something that i having running around in the past few days.. the fact that there is no way to access an associated model from within a reflection / association scope. There are many tickets that share this basic problem, this #3027 ticket would be easily solved if there was any kind of access to the associated model (and therefore AR::Base.table_name).
    Solving this issue can clear some significant amount of tickets.

  • Elad Meidar

    Elad Meidar September 26th, 2009 @ 07:52 AM

    • Tag changed from bugmash to bugmash, patch
  • Rizwan Reza

    Rizwan Reza January 21st, 2010 @ 07:17 AM

    • Milestone cleared.
    • Tag changed from bugmash, patch to activerecord, dependent, patch
    • State changed from “new” to “open”
    • Assigned user set to “Pratik”
  • Rizwan Reza

    Rizwan Reza March 28th, 2010 @ 07:08 PM

    • State changed from “open” to “resolved”
  • Jeremy Kemper

    Jeremy Kemper October 15th, 2010 @ 11:01 PM

    • Milestone set to 3.0.2
    • Importance changed from “” to “Low”

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