[Rails] Re: Problems migrating from Postgres to MySQL

[David Mitchell]

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.
>