Rick Olson wrote:
One way the developer can deal with this (what I've been muddling through in a
tough spot in my case, in fact) is to do things like:
def self.up
# ...
ActiveRecord::Base.connection.select_all(...).each do |foo|
execute "insert into bar (...) values (...)"
end
Blech.
But, this doesn't catch everything (the before_save example is unhelped, e.g.).
Ultimately, the developer can't (and shouldn't have to) predict what the future
is going to bring, and shouldn't have to code around this sort of problem.
RIck, I've been running into this with Mephisto, a little blogging app
I've been writing on the side. After a pretty intense weekend of
hacking, I found myself doing a lot of db restructuring. Obviously,
the earlier migrations weren't working, because the model and or table
has been renamed.
To work around this, I just started creating temporary models per
migration. I find that much nicer than reverting to
ActiveRecord::Base.connection for my delicate sql needs. It might be
best to create the temporary model classes inside the migration class
to keep them from clashing. This temp model gives me a nicer way to
manage the data, and frees me from worrying about filters,
validations, changing method names, etc.
I may throw together some task that takes my initial schema and runs
through all the migrations eventually. I think this kind ability is
important for packaged apps, so I'll certainly share any progress I
make in Mephisto.
Take a look: http://techno-weenie.net/svn/projects/mephisto/trunk/db/migrate/
That's what I do too, like in
http://techno-weenie.net/svn/projects/mephisto/trunk/db/migrate/012_rename_categories_to_sections.rb
The only difference, is that I use two classes instead of one, one for the up
and one for the down, in case they are different. And I also give them a unique
name that uses the migration's name. This is in case all the migrations are run
from 1-N to allow for the possibility that the same table will be modified in
different migrations.
class Section_Migrate003Up < ActiveRecord::Base
set_table_name 'output_state'
end
class Section_Migrate003Down < ActiveRecord::Base
set_table_name 'output_state'
end
Regards,
Blair
--
Blair Zajac, Ph.D.
<[EMAIL PROTECTED]>
Subversion training, consulting and support
http://www.orcaware.com/svn/
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