[LRUG] Multiple databases, migration, integration...

[Riccardo Tacconi]

This is interesting but I do not think that you can INSERT data in a view in
MySql. Am I wrong?

On Fri, Jan 8, 2010 at 11:15 AM, Andrew McDonough <
andrew at andrewmcdonough.co.uk> wrote:

> Disclaimer: my suggestion might be a really bad idea (I only just
> tried it and have certainly never used it in production).  I'd like to
> hear what other people think though, as it's something I've considered
> in the past to port our numerous legacy PHP apps to rails.  It does
> appear to work though.
>
> Use MySQL views:
> You could use MySQL views to create rails friendly views of the
> database tables.  You would then write the classes assuming that
> everything is named as rails likes it.  For example, assuming two
> simple tables in the old database, "user" and "dept", you could create
> views called users and departments:
>
> CREATE TABLE user (
>  userID int(11) NOT NULL auto_increment,
>  name varchar(255),
>  deptID int(11),
>  PRIMARY KEY  (userID)
> ) TYPE=MyISAM;
>
> CREATE TABLE dept (
>  deptID int(11) NOT NULL auto_increment,
>  name varchar(255),
>  PRIMARY KEY  (deptID)
> ) TYPE=MyISAM;
>
>
> CREATE VIEW users as select userID as id, name, deptID as
> department_id FROM user;
> CREATE VIEW departments as select deptID as id, name FROM dept;
>
> Then in your model:
>
> class Department < ActiveRecord::Base
>  has_many :users
> end
>
> class User < ActiveRecord::Base
>  belongs_to :department
> end
>
> I've tried creating, saving and loading both of these entities and
> querying the associations between them, and it appears to work.  The
> advantage of this is you could write clean model code, and assume well
> named tables, meaning if you ever decide to migrate the database to a
> rails naming convention, you wouldn't need to touch your code.  The
> disadvantages are that you would end up with twice as many table
> views, and you would need to maintain two things for each table (e.g.
> adding a field would mean adding it to both the table and the view).
> Again, I have only tested this for two simple tables.  It might break
> for more complex schemas, but I thought it was worth investigating.
>
> Regards,
>
> Andrew McDonough
>
>
>
> 2010/1/8 Andrew Stewart <boss at airbladesoftware.com>:
> >
> > On 8 Jan 2010, at 10:33, Riccardo Tacconi wrote:
> >>
> >> Yesterday I decided to refactor a page developed in PHP with Rails. I am
> >> using two MySql databases, one for the PHP, one for Rails. Now I am not
> sure
> >> if I should use only one database or two. The DB for PHP has name in the
> >> singular form (dept, user, article...), the primary keys are something
> like
> >> 'deptID', 'user_id', in few words is an old rubbish inherited DB.
> >
> > I am working in a similar situation where I am running an old Mambo (PHP)
> > site alongside a new Rails site, while slowly moving functionality from
> the
> > former to the latter.
> >
> > I have a single MySQL database containing both the PHP system's tables
> and
> > the Rails app's tables.  This way I only need to connect to a single
> > database, which is the way Rails likes it.  To avoid table name clashes I
> > prefixed all the Rails app's tables with a simple prefix, configuring
> > ActiveRecord appropriately (c.f. the table_name_prefix method).
> >
> > Have a class for each PHP table you need to use, and use ActiveRecord's
> > table_name and primary_key methods to cope with the old table names.  I
> do
> > this and it all works perfectly.
> >
> > When I want to move functionality and data from PHP-land to Rails-land, I
> > use Tim Riley's marvellous acts_as_importable plugin.  He came up with an
> > excellent pattern for migrating data, and for my system it works very
> well.
> >
> > http://github.com/timriley/acts-as-importable
> >
> > Regards,
> >
> > Andy Stewart
> > -------
> > http://airbladesoftware.com
> >
> > _______________________________________________
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> >
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-- 
Riccardo Tacconi
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