Open Stack

Yes, I agree. 

Actually, I am trying to infer what the "programming model" for this is as we go along. 

Personally I would have been happy with only marking the fields when they are set. Then, if a you want to change a list somehow you would get it and then set it again, e.g.: 
  mylist = object.alist	
  do something to mylist
  object.alist = mylist
  object.save()

Having said that, it can be convenient to use the data structures in place. In which case we need all these means to track the changes and they should go in the base classes so they are used consistently.

So in short, I am happy with your dirty children :)

Paul.

-----Original Message-----
From: Dan Smith [mailto:dms at danplanet.com] 
Sent: 13 January 2014 15:26
To: Murray, Paul (HP Cloud Services); Wang, Shane; OpenStack Development Mailing List (not for usage questions)
Cc: Lee, Alexis; Tan, Lin
Subject: Re: [Nova] Detect changes in object model

> ObjectListBase has a field called objects that is typed 
> fields.ListOfObjectsField('NovaObject'). I can see methods for count 
> and index, and I guess you are talking about adding a method for "are 
> any of your contents changed" here. I don't see other list operations 
> (like append, insert, remove, pop) that modify the list. If these were 
> included they would have to mark the list as changed so it is picked 
> up when looking for changes.
> 
> Do you see these belonging here or would you expect those to go in a 
> sub-class if they were wanted?

Well, I've been trying to avoid implying the notion that a list of things represents the content of the database. Meaning, I don't think it makes sense for someone to get a list of Foo objects, add another Foo to the list and then call save() on the list. I think that ends up with the assumption that the list matches the contents of the database, and if I add or remove things from the list, I can save() the contents to the database atomically. That definitely isn't something we can or would want to support.

That said, if we make the parent object consider the child to be dirty if any of its contents are dirty or the list itself is dirty (i.e. the list of objects has changed) that should give us the desired behavior for change tracking, right?

--Dan