I have a task to import old data from old DB to new Rails app. Old program was created in Delphi and is outdated so customer decided create rails app for replacing it. I have dump file, and I am creating local MySQL db now and inserting there data for last 8 years (mysql is working for over an hour already) :)
Now I am not sure about the way old data should be imported. The problem is that old db tables and columns are named differently from what I have in my App and there are many of unused and unneeded columns/tables there. So I need select only some of them and insert into App DB. Could You please suggest the best solution for this case?
Thank you in advance!
You can adjust old db to rails app and work with it
Let's imagine you have old DB with the following table old_posts
old_posts
________________________________________
sysid | name | description |
_______________________________________
| | |
1 | The best post| Some description |
_______________________________________
| | |
2 | Another post| Another descrip |
________________________________________
In rails you can define table_name with
More information in doc:
http://api.rubyonrails.org/classes/ActiveRecord/ModelSchema/ClassMethods.html#method-i-table_name
Also you can redifine attributes with alias_attribute
More information in doc:
http://api.rubyonrails.org/classes/Module.html#method-i-alias_attribute
To change primary key primary_key
More information in doc:
http://api.rubyonrails.org/classes/ActiveRecord/AttributeMethods/PrimaryKey/ClassMethods.html#method-i-primary_key-3D
The example will be seems as
class Post < ActiveRecord::Base
self.primary_key = 'sysid'
self.table_name = 'old_posts`
alias_attribute :name, :title
alias_attribute :description, :content
end
Then you can invoke:
p = Post.find(1)
p.title #= > The best post
Also you can use legacy database separately from rails app database