I have another patch which addresses this issue and also nonexistent Mysql::Error#error method. It also deals with situation when we use old mysql gem and 'uninitialized constant Mysql2' message gets raised.

I can confirm Marjan Krekoten' s patch is working for me ( haven't tried the other one ), but it is rather unpleasant having to modifing database.rake... perhaps the patch should be included into rails right away, not forcing mysql users to hack into activerecord files.

I agree with José Valim. It probably would be better to do somthing like this

class Mysql2::Error
    # ...
    alias_method :errno, :error_number
    alias_method :error, :message
end

But following is still needed, because it avoids 'uninitialized constant Mysql2' when we use mysql instead of mysql2:

error_class = "#{config['adapter'].capitalize}::Error".constantize

I can edit this patch and also make patch for mysql2 if José Valim and Brian Lopez agree with this.

Hey guys,
I added the aliases here: http://github.com/brianmario/mysql2/commit/98fbeb6f64e562e9889346d4...

Cool! I've updated patch to fix 'uninitialized constant Mysql2'. But this problem will go away completely with new release of mysql2 gem.

I'll try and push 0.2.4 by tonight

Is there a non hacky way for a rails mortal like me to resolve this problem? I have updated to rails 3 today and have since not been able to do any development. Thanks.

Any progress on this issue? I'm new to Rails and (like jw) this has held me up for almost a week now. Is there an easy workaround? Thanks.

Well we need to wait for next release of mysql2. It will introduce compatibility with mysql gem. Or you can point your Gemfile to mysql2 git repo.

mysql2 v0.2.4 released with mysql compatibility fix. So I think we should update development and generated Gemfile to use >= 0.2.4. I've attached a patch.

Currently the Gemfile uses 0.2.6. The rest hasn't been applied yet. Was the issue resolved?

Hi, I'm running rails 3.0.3, ruby 1.9.2p0, mysql 5.1.53, and when i run rake db:create I get the following:

** Invoke db:create (first_time)
** Invoke db:load_config (first_time)
** Invoke rails_env (first_time)
** Execute rails_env
** Execute db:load_config
** Execute db:create
rake aborted!
uninitialized constant Mysql
/Users/John/.rvm/gems/ruby-1.9.2-p0/gems/rspec-core-2.0.1/lib/rspec/core/backward_compatibility.rb:20:in `const_missing'
/Users/John/.rvm/gems/ruby-1.9.2-p0/gems/rspec-expectations-2.0.1/lib/rspec/expectations/backward_compatibility.rb:6:in `const_missing'
/Users/John/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.0.3/lib/active_record/railties/databases.rake:64:in `rescue in create_database'
/Users/John/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.0.3/lib/active_record/railties/databases.rake:39:in `create_database'
/Users/John/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.0.3/lib/active_record/railties/databases.rake:33:in `block (2 levels) in <top (required)>'
/Users/John/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.8.7/lib/rake.rb:636:in `call'
/Users/John/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.8.7/lib/rake.rb:636:in `block in execute'
/Users/John/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.8.7/lib/rake.rb:631:in `each'
/Users/John/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.8.7/lib/rake.rb:631:in `execute'
/Users/John/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.8.7/lib/rake.rb:597:in `block in invoke_with_call_chain'
/Users/John/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/1.9.1/monitor.rb:201:in `mon_synchronize'
/Users/John/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.8.7/lib/rake.rb:590:in `invoke_with_call_chain'
/Users/John/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.8.7/lib/rake.rb:583:in `invoke'
/Users/John/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.8.7/lib/rake.rb:2051:in `invoke_task'
/Users/John/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.8.7/lib/rake.rb:2029:in `block (2 levels) in top_level'
/Users/John/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.8.7/lib/rake.rb:2029:in `each'
/Users/John/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.8.7/lib/rake.rb:2029:in `block in top_level'
/Users/John/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_exception_handling'
/Users/John/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.8.7/lib/rake.rb:2023:in `top_level'
/Users/John/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.8.7/lib/rake.rb:2001:in `block in run'
/Users/John/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_exception_handling'
/Users/John/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.8.7/lib/rake.rb:1998:in `run'
/Users/John/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.8.7/bin/rake:31:in `<top (required)>'
/Users/John/.rvm/gems/ruby-1.9.2-p0/bin/rake:19:in `load'
/Users/John/.rvm/gems/ruby-1.9.2-p0/bin/rake:19:in `<main>'

My gems are:

*** LOCAL GEMS ***

abstract (1.0.0)
actionmailer (3.0.3, 3.0.0)
actionpack (3.0.3, 3.0.0)
activemodel (3.0.3, 3.0.0)
activerecord (3.0.3, 3.0.0)
activeresource (3.0.3, 3.0.0)
activesupport (3.0.3, 3.0.0)
addressable (2.2.2)
arel (2.0.6, 1.0.1)
bcrypt-ruby (2.1.2)
builder (2.1.2)
bundler (1.0.2)
cgi_multipart_eof_fix (2.5.0)
configuration (1.2.0, 1.1.0)
cucumber (0.10.0, 0.9.3)
cucumber-rails (0.3.2)
daemons (1.1.0, 1.0.10)
database_cleaner (0.6.0)
devise (1.1.5, 1.1.3)
diff-lcs (1.1.2)
erubis (2.6.6)
faraday (0.5.3)
fastthread (1.0.7)
gem_plugin (0.2.3)
gherkin (2.3.2, 2.2.9)
i18n (0.5.0, 0.4.1)
jasmine (1.0.1.1, 1.0.1)
json (1.4.6)
json_pure (1.4.6)
launchy (0.3.7)
mail (2.2.12, 2.2.7)
mime-types (1.16)
mongrel (1.2.0.pre2)
multi_json (0.0.5)
multipart-post (1.0.1)
mysql2 (0.2.6)
net-ldap (0.1.1)
nokogiri (1.4.4, 1.4.3.1)
oa-basic (0.1.6)
oa-core (0.1.6)
oa-enterprise (0.1.6)
oa-oauth (0.1.6)
oa-openid (0.1.6)
oauth (0.4.4)
oauth2 (0.1.0)
omniauth (0.1.6)
pg (0.9.0)
polyglot (0.3.1)
pyu-ruby-sasl (0.0.3.2)
rack (1.2.1)
rack-mount (0.6.13)
rack-openid (1.2.0)
rack-test (0.5.6)
rails (3.0.3, 3.0.0)
railties (3.0.3, 3.0.0)
rake (0.8.7)
rest-client (1.6.1)
rspec (2.0.1)
rspec-core (2.0.1)
rspec-expectations (2.0.1)
rspec-mocks (2.0.1)
rspec-rails (2.0.1)
ruby-openid (2.1.8)
ruby-openid-apps-discovery (1.2.0)
rubyntlm (0.1.1)
selenium-client (1.2.18)
selenium-rc (2.2.4)
spork (0.8.4)
term-ansicolor (1.0.5)
thor (0.14.6, 0.14.3)
treetop (1.4.9, 1.4.8)
tzinfo (0.3.23)
warden (1.0.2, 0.10.7)
webrat (0.7.2)

I am having the same issue. Any ideas guys?

root@localhost:/var/ruby/testapp# rake db:create --trace
(in /var/ruby/testapp) Invoke db:create (first_time) Invoke db:load_config (first_time) Invoke rails_env (first_time) Execute rails_env Execute db:load_config Execute db:create rake aborted!
uninitialized constant Mysql2
/usr/lib/ruby/gems/1.8/gems/activerecord-3.0.3/lib/active_record/railties/databases.rake:64:in create_database' /usr/lib/ruby/gems/1.8/gems/activerecord-3.0.3/lib/active_record/railties/databases.rake:33 /usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:636:incall' /usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:636:in execute' /usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:631:ineach' /usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:631:in execute' /usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:597:ininvoke_with_call_chain' /usr/lib/ruby/1.8/monitor.rb:242:in synchronize' /usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:590:ininvoke_with_call_chain' /usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:583:in invoke' /usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2051:ininvoke_task' /usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in top_level' /usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:ineach' /usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in top_level' /usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:instandard_exception_handling' /usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2023:in top_level' /usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2001:inrun' /usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in standard_exception_handling' /usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:1998:inrun' /usr/lib/ruby/gems/1.8/gems/rake-0.8.7/bin/rake:31 /usr/bin/rake:19:in load' /usr/bin/rake:19

Hi guys

I am having the same issue at the moment. I am running Rails 3.0.3

Local Gems:

 LOCAL GEMS 







abstract (1.0.0)
actionmailer (3.0.3)
actionpack (3.0.3)
activemodel (3.0.3)
activerecord (3.0.3)
activeresource (3.0.3)
activesupport (3.0.3)
arel (2.0.6)
builder (2.1.2)
bundler (1.0.7)
columnize (0.3.2)
erubis (2.6.6)
i18n (0.5.0)
linecache (0.43)
mail (2.2.13)
mime-types (1.16)
mysql (2.8.1)
mysql2 (0.2.6)
polyglot (0.3.1)
rack (1.2.1)
rack-mount (0.6.13)
rack-test (0.5.6)
rails (3.0.3)
railties (3.0.3)
rake (0.8.7)
ruby-debug (0.10.4)
ruby-debug-base (0.10.4)
ruby-debug-ide (0.4.16)
sqlite3-ruby (1.3.2)
SystemTimer (1.2.1)
thor (0.14.6)
treetop (1.4.9)
tzinfo (0.3.23)

Database config:

development:
  adapter: mysql2
  encoding: utf8
  database: testapp_development
  pool: 5
  username: root
  password: tax1Rank
  socket: /tmp/mysql.sock

Warning: The database defined as "test" will be erased and

re-generated from your development database when you run "rake".

Do not set this db to the same as development or production.

test:
  adapter: mysql2
  encoding: utf8
  database: testapp_test
  pool: 5
  username: root
  password: tax1Rank
  socket: /tmp/mysql.sock



production:
  adapter: mysql2
  encoding: utf8
  database: testapp_production
  pool: 5
  username: root
  password: tax1Rank
  socket: /tmp/mysql.sock

Rake with trace:

(in /var/ruby/testapp)
 Invoke db:create (first_time)
 Invoke db:load_config (first_time)
 Invoke rails_env (first_time)
 Execute rails_env
 Execute db:load_config
 Execute db:create
rake aborted!
uninitialized constant Mysql2
/usr/lib/ruby/gems/1.8/gems/activerecord-3.0.3/lib/active_record/railties/databases.rake:64:in create_database'
/usr/lib/ruby/gems/1.8/gems/activerecord-3.0.3/lib/active_record/railties/databases.rake:33
/usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:636:incall'
/usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:636:in execute'
/usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:631:ineach'
/usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:631:in execute'
/usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:597:ininvoke_with_call_chain'
/usr/lib/ruby/1.8/monitor.rb:242:in synchronize'
/usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:590:ininvoke_with_call_chain'
/usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:583:in invoke'
/usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2051:ininvoke_task'
/usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in top_level'
/usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:ineach'
/usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in top_level'
/usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:instandard_exception_handling'
/usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2023:in top_level'
/usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2001:inrun'
/usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in standard_exception_handling'
/usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:1998:inrun'
/usr/lib/ruby/gems/1.8/gems/rake-0.8.7/bin/rake:31
/usr/bin/rake:19:in load'
/usr/bin/rake:19</code>
</pre>

This patch should help.

You can see my blog post, may be it helps : http://geryit.com/blog/2011/01/installing-mysql-with-rails-on-mac-o...