[Rails] Re: Problems migrating from Postgres to MySQL

[David Mitchell]

Thanks Pat,

Actually this was my first chance to use migrations, and it worked
reasonably well - made things a lot easier.  Following through the
migrations video made things a lot simpler.

The biggest problem I had was the lack of referential information that
comes out of rake when there's a problem with the migration code - it
can be tough to spot a problem when you're trawling through hundreds
of lines of create_table / t_column statements that all blur together
after a while...

Regards

Dave M.

On 01/02/06, Pat Maddox <pergesu at gmail.com> wrote:
> Glad to hear you got it working.
>
> Just so you know, there's no need to copy the generated schema file
> into a new migration.  Just leave it in db/schema.rb and do rake
> db_schema_import to create the database.  It generates a schema_info
> table to hold the version, so you can just do migrations normally
> after that.
>
> Pat
>
> On 1/31/06, David Mitchell <monch1962 at gmail.com> wrote:
> > OK I think I got it sorted - it was probably due to an update that I
> > did to (something) that had caused the wires to get crossed on the
> > system.  The box hadn't been rebooted for nearly 4 months, and
> > possibly a library update had crept by me unnoticed.
> >
> > A reboot fixed it.
> >
> > Regards
> >
> > Dave M.
> >
> > On 31/01/06, David Mitchell <monch1962 at gmail.com> wrote:
> > > Hello everyone,
> > >
> > > I'm trying to migrate a working app from Postgres to MySQL, and I'm
> > > trying to use a migration to get it done rather than alter all my
> > > database table creation scripts to MySQL syntax.  I've done loads of
> > > work with Postgres, but am a real newbie with MySQL...
> > >
> > > I did a 'rake db_schema_dump' from my Postgres app, and got a nice
> > > looking schema file with all my tables and fields, exactly as
> > > expected.  I then created a migration file, pasted the schema info
> > > into the self.up section in the schema file and made sure there were
> > > no obvious problems.  So far, so good.
> > >
> > > I then did a 'gem install mysql', created a new MySQL database, set up
> > > a MySQL user, tweaked database.yml to point to the new MySQL database
> > > and tried a 'rake db_schema_import'.
> > >
> > > Wham!  Loads of warnings, ending in an 'uninitialized constant Mysql'.
> > >  I've confirmed that the database.yml file is OK.  I then did a 'rake
> > > db_schema_import --trace'; here's what I think is the relevant section
> > > of the output:
> > >
> > > ** Invoke db_schema_import (first_time)
> > > ** Invoke environment (first_time)
> > > ** Execute environment
> > > ** Execute db_schema_import
> > > rake aborted!
> > > uninitialized constant Mysql
> > > /usr/lib/ruby/gems/1.8/gems/activesupport-1.2.5/lib/active_support/dependencies.rb:200:in
> > > `const_missing'
> > > /usr/lib/ruby/gems/1.8/gems/activerecord-1.13.2/lib/active_record/connection_adapters/mysql_adapter.rb:35:in
> > > `mysql_connection'
> > > /usr/lib/ruby/gems/1.8/gems/activerecord-1.13.2/lib/active_record/connection_adapters/abstract/connection_specification.rb:145:in
> > > `connection_without_query_cache='
> > > /usr/lib/ruby/gems/1.8/gems/activerecord-1.13.2/lib/active_record/query_cache.rb:54:in
> > > `connection='
> > > /usr/lib/ruby/gems/1.8/gems/activerecord-1.13.2/lib/active_record/connection_adapters/abstract/connection_specification.rb:106:in
> > > `retrieve_connection'
> > > /usr/lib/ruby/gems/1.8/gems/activerecord-1.13.2/lib/active_record/connection_adapters/abstract/connection_specification.rb:20:in
> > > `connection'
> > > /usr/lib/ruby/gems/1.8/gems/activerecord-1.13.2/lib/active_record/migration.rb:170:in
> > > `method_missing'
> > > ./db/schema.rb:7
> > > /usr/lib/ruby/gems/1.8/gems/activerecord-1.13.2/lib/active_record/schema.rb:43:in
> > > `define'
> > > ./db/schema.rb:5
> > > /usr/lib/ruby/gems/1.8/gems/activesupport-1.2.5/lib/active_support/dependencies.rb:207:in
> > > `load'
> > > /usr/lib/ruby/gems/1.8/gems/rails-1.0.0/lib/tasks/databases.rake:27
> > > /usr/lib/ruby/site_ruby/1.8/rake.rb:232:in `execute'
> > > /usr/lib/ruby/site_ruby/1.8/rake.rb:232:in `execute'
> > > /usr/lib/ruby/site_ruby/1.8/rake.rb:202:in `invoke'
> > > /usr/lib/ruby/1.8/thread.rb:135:in `synchronize'
> > > /usr/lib/ruby/site_ruby/1.8/rake.rb:195:in `invoke'
> > > /usr/lib/ruby/site_ruby/1.8/rake.rb:1719:in `run'
> > > /usr/lib/ruby/site_ruby/1.8/rake.rb:1719:in `run'
> > > /usr/bin/rake:8
> > >
> > > I poked around in Google and found a few people have seen the
> > > 'uninitialized constant Mysql' error, but these always seem to be due
> > > to using old versions of Rails, gems or MySQL.  I'm running the latest
> > > Rails, just updated all gems, and MySQL 5.1, so I can't see that I've
> > > got any old stuff left.
> > >
> > > Has anyone got any suggestions?
> > >
> > > Thanks in advance
> > >
> > > Dave M.
> > >
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