thr3ads.net - Rails - Generating Migration Files With DATA Changes [Sep 2006]

If this information is useful, please help other people find it:
Share via:

Caleb

2006-Sep-13 21:40 UTC

Generating Migration Files With DATA Changes

I would like to leverage the Rails migration functionality but use it 
for producing migrate files that migrate DATA changes instead of SCHEMA 
changes.  For an example, instead of having:

class MigrateName < ActiveRecord::Migration
  def self.up
    add_column :users, :new_user_column, :float
  end

  def self.down
    remove_column :users, :new_user_column
  end
end

I need something like:

class MigrateName < ActiveRecord::Migration
  def self.up
    User.create({:id => 5, :name => "John"})
    User.create({:id => 6, :name => "John2"})
    User.delete(1)
    User.update(2, {:name => "Mary_after"})
  end

  def self.down
    User.delete(5)
    User.delete(6)
    User.create({:id => 1, :name => "Jack"})
    User.update(2, {:name => "Mary_before"})
  end
end

This way running ''rake migrate'' will update to the latest DATA
SET.
Anyone try to do something like this before?  Is this a good way to go 
about doing this?  I know I could just do DB dumps to flat files, but 
these databses could get quite large and I would like to have 
''relatively'' small migrate files that are much more usable
than flat DB
dumps.

Another way I thought of doing this was to produce patch files from 
running diff and keep track of these.  However, something like the above 
seemed more elegant.

The tricky part here is that in order to produce these migrate files, I 
need to be able to have two different databases to compare against.  How 
can I use one ActiveRecord class but programmatically switch what DB it 
is pointing at?  I imagine that some sort of factory would be needed for 
this.  For example:

user_from_db1 = ObjectFactory(User.find_by_id(22), "DB1")
user_from_db2 = ObjectFactory(User.find_by_id(22), "DB2")

user_from_db1.name # "Fred"
user_from_db2.name # "Alice"

At this point I could then determine what to write in both the self.up 
and self.down methods above if I were iterating through each user to see 
how DB1 and DB2 were different.

This looks like it will be somewhat complex, so I''m mainly looking to 
see if anyone has successfully tackled this before or if anyone knows of 
a better way to do this.

-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk
-~----------~----~----~----~------~----~------~--~---

Mr. Interweb

2006-Sep-13 22:18 UTC

head link

Re: Generating Migration Files With DATA Changes

I hate to say it, but my guess as to how to do this best would be to
copy your table to a backup table.  Then, apply your data changes.  To
roll back all you would have to do would be to drop or empty the
current table and restore the old backup.  I would think that would be
the easiest way.


Caleb wrote:> I would like to leverage the Rails migration functionality but use it
> for producing migrate files that migrate DATA changes instead of SCHEMA
> changes.  For an example, instead of having:
>
> class MigrateName < ActiveRecord::Migration
>   def self.up
>     add_column :users, :new_user_column, :float
>   end
>
>   def self.down
>     remove_column :users, :new_user_column
>   end
> end
>
> I need something like:
>
> class MigrateName < ActiveRecord::Migration
>   def self.up
>     User.create({:id => 5, :name => "John"})
>     User.create({:id => 6, :name => "John2"})
>     User.delete(1)
>     User.update(2, {:name => "Mary_after"})
>   end
>
>   def self.down
>     User.delete(5)
>     User.delete(6)
>     User.create({:id => 1, :name => "Jack"})
>     User.update(2, {:name => "Mary_before"})
>   end
> end
>
> This way running ''rake migrate'' will update to the latest
DATA SET.
> Anyone try to do something like this before?  Is this a good way to go
> about doing this?  I know I could just do DB dumps to flat files, but
> these databses could get quite large and I would like to have
> ''relatively'' small migrate files that are much more
usable than flat DB
> dumps.
>
> Another way I thought of doing this was to produce patch files from
> running diff and keep track of these.  However, something like the above
> seemed more elegant.
>
> The tricky part here is that in order to produce these migrate files, I
> need to be able to have two different databases to compare against.  How
> can I use one ActiveRecord class but programmatically switch what DB it
> is pointing at?  I imagine that some sort of factory would be needed for
> this.  For example:
>
> user_from_db1 = ObjectFactory(User.find_by_id(22), "DB1")
> user_from_db2 = ObjectFactory(User.find_by_id(22), "DB2")
>
> user_from_db1.name # "Fred"
> user_from_db2.name # "Alice"
>
> At this point I could then determine what to write in both the self.up
> and self.down methods above if I were iterating through each user to see
> how DB1 and DB2 were different.
>
> This looks like it will be somewhat complex, so I''m mainly looking
to
> see if anyone has successfully tackled this before or if anyone knows of
> a better way to do this.
> 
> -- 
> Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk
-~----------~----~----~----~------~----~------~--~---

_Kevin

2006-Sep-13 22:19 UTC

head link

Re: Generating Migration Files With DATA Changes

Caleb wrote:> I would like to leverage the Rails migration functionality but use it
> for producing migrate files that migrate DATA changes instead of SCHEMA
> changes.  For an example, instead of having:
>
> class MigrateName < ActiveRecord::Migration
>   def self.up
>     add_column :users, :new_user_column, :float
>   end
>
>   def self.down
>     remove_column :users, :new_user_column
>   end
> end
>
> I need something like:
>
> class MigrateName < ActiveRecord::Migration
>   def self.up
>     User.create({:id => 5, :name => "John"})
>     User.create({:id => 6, :name => "John2"})
>     User.delete(1)
>     User.update(2, {:name => "Mary_after"})
>   end
>
>   def self.down
>     User.delete(5)
>     User.delete(6)
>     User.create({:id => 1, :name => "Jack"})
>     User.update(2, {:name => "Mary_before"})
>   end
> end
>
> This way running ''rake migrate'' will update to the latest
DATA SET.
> Anyone try to do something like this before?  Is this a good way to go
> about doing this?  I know I could just do DB dumps to flat files, but
> these databses could get quite large and I would like to have
> ''relatively'' small migrate files that are much more
usable than flat DB
> dumps.
>
> Another way I thought of doing this was to produce patch files from
> running diff and keep track of these.  However, something like the above
> seemed more elegant.
>
> The tricky part here is that in order to produce these migrate files, I
> need to be able to have two different databases to compare against.  How
> can I use one ActiveRecord class but programmatically switch what DB it
> is pointing at?  I imagine that some sort of factory would be needed for
> this.  For example:
>
> user_from_db1 = ObjectFactory(User.find_by_id(22), "DB1")
> user_from_db2 = ObjectFactory(User.find_by_id(22), "DB2")
>
> user_from_db1.name # "Fred"
> user_from_db2.name # "Alice"
>
> At this point I could then determine what to write in both the self.up
> and self.down methods above if I were iterating through each user to see
> how DB1 and DB2 were different.
>
> This looks like it will be somewhat complex, so I''m mainly looking
to
> see if anyone has successfully tackled this before or if anyone knows of
> a better way to do this.
>
> --
> Posted via http://www.ruby-forum.com/.
Migrations can pretty much run arbitrary code in the up and down
methods.  The only time it''s an issue is if you change the model and
then try to manipulate objects in the same migraiton.

It should not be too difficult to have a migration load a fixture into
a database table from a YAML file.

_Kevin


--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk
-~----------~----~----~----~------~----~------~--~---

Rails - Sep 2006 - Generating Migration Files With DATA Changes

Generating Migration Files With DATA Changes

Re: Generating Migration Files With DATA Changes

Re: Generating Migration Files With DATA Changes