Defaulting values of new fields on existing documents

[nader]

Before I work on a patch, I wanted to get the community's opinion on
this.

I run into this issue all the time, where I add a new field to my
mongoid document definition with a default value. The default value
applies to new documents, but not to existing documents.

I think that if you set a default value and you request that field on
a document it should return the value even it didn't have it
originally.

What do you guys think?

[James Harton]

I would tend to agree with your thesis; this caused a lot of headaches for me recently. You can always make it a separate plugin if others don't like it.

James Harton
@jamesotron

[Doug Mayer]

+1 for this behavior. We might want the ability to see if a particular
field is being defaulted (is it null in the DB?), or perhaps a way to
not default it, but I think what you describe would be the expected
behavior.

[Jacques Crocker]

This is a really good idea and something I personally need as well. However I think it work better as some sort of migration rake task.

rake mongoid:set_defaults

Something that scans through all the records for the association collection on each model and sets the default fields if not already set.

[Andrew Coldham]

+1 for Jacques method. Minimize surprises. (E.g. if you set the default value after a read, is the object dirty? It definitely needs to be saved.)

[nader]

Great. I agree with the Jacques method. Simple and surprise free.
I'll try and work on the rake task this weekend. If anyone wants to
help let me know.

On Oct 19, 7:19 pm, Andrew Coldham <andrewcold...@gmail.com> wrote:
> +1 for Jacques method. Minimize surprises. (E.g. if you set the default value after a read, is the object dirty? It definitely needs to be saved.)
>

[Bradley Grzesiak]

what about something like:

class Foo

  include Mongoid::Document

  include Mongoid::Migrations

  field :bar, :default => ''

end

class FooMigration

  migrate :bar, :from => nil

end

Perhaps no rake task would be necessary?

:brad

--
Bradley Grzesiak
co-founder, bendyworks llc
http://bendyworks.com/

[nader]

Brad, I prefer the rake task. You can just add it to your deploy
process and everything will be defaulted. I can see a case for adding
something to the field to indicate that you don't want to migrate that
field in existing docs though. But that would be the exception in
most cases.

[nader]

Hi everyone, here's the first draft of the rake task: http://gist.github.com/641569

Improvement suggestions very welcome.

Couple things to note.
1) I dropped down to the Ruby driver, because I don't know how to
update all the docs in a collection with one call using Mongoid.
2) This currently only works for top level documents. I don't think
there is a way to update all embedded docs without looping through the
individual parent documents? So maybe that is the better approach?
Seems like it will be a serious performance hit with a large set of
documents.

Jacques, where's the best place to put this? Just in the Rakefile?

Nader

[nader]

OK, Jacques I found the database.rake file, not sure how I missed that
earlier.

So here is the rake task: http://github.com/iamnader/mongoid/commit/ffb5a2b05202fe14e3b6b397382b02fcf402081f

Let me know if anyone has any feedback before I send the pull request.

I'll try and work on adding support for embedded documents today.

[nader]

OK, I got this working with embedded documents. Turned out to be more
complicated than I anticipated due to positional operators only
updating the first match and unexpected cases with deeply nested
documents (like if the nested document doesn't exist at all on some of
the parent docs.

Sent a pull request: http://github.com/mongoid/mongoid/pull/416

On Oct 25, 11:27 am, nader <iamna...@gmail.com> wrote:
> OK, Jacques I found the database.rake file, not sure how I missed that
> earlier.
>

> So here is the rake task:http://github.com/iamnader/mongoid/commit/ffb5a2b05202fe14e3b6b397382...

[nader]

Updated this with better exception handling. Still needs to be pulled
in

> > > > > > collection on each model and sets thedefaultfields if not already set.

>
> > > > > > > > On Oct 19, 2010, at 5:53 PM, nader wrote:
>
> > > > > > > >> Before I work on a patch, I wanted to get the community's opinion on
> > > > > > > >> this.
>
> > > > > > > >> I run into this issue all the time, where I add a new field to my
> > > > > > > >> mongoid document definition with adefaultvalue.  Thedefaultvalue
> > > > > > > >> applies to new documents, but not to existing documents.
>

> > > > > > > >> I think that if you set adefaultvalue and you request that field on

[JDeville]

Are you sure this is working w/ embedded documents? It's been
absurdly helpful for me so far, but I've got a problem now with it not
updating embedded schemas.

Here's what I have:

class User
include Mongoid::Document
include Mongoid::Timestamps
embeds_many :interests, :class_name => "Interest"
end

class Interest
include Mongoid::Document
embedded_in :user, :inverse_of => :interests
identity :type => String
field :name
field :category
field :created_by, :default => "fb"

attr_accessible :name, :category, :_id, :created_by
end

The new field is :created_by, but the field isn't being created and
initialized.

Thanks
-Jeff