I can't run "bundle update" because of "mysql2" gem - mysql

Question

I have this in the Gemfile:
gem 'mysql2'
But when I run bundle update, I get this error message:
An error occurred while installing mysql2 (0.3.16), and Bundler cannot continue.
Make sure that `gem install mysql2 -v '0.3.16'` succeeds before bundling.
I've tried to move this into the production section, like this:
group :production do
gem 'mysql2'
end
But after running bundle update, the result is the same. This section is processed only in the production mode, or not?
How to get rid of this error message on localhost?
EDIT: The whole error message:
Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.
/Users/radek/.rvm/rubies/ruby-1.9.3-p385/bin/ruby extconf.rb
checking for ruby/thread.h... *** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers. Check the mkmf.log file for more
details. You may need configuration options.
Provided configuration options:
--with-opt-dir
--with-opt-include
--without-opt-include=${opt-dir}/include
--with-opt-lib
--without-opt-lib=${opt-dir}/lib
--with-make-prog
--without-make-prog
--srcdir=.
--curdir
--ruby=/Users/radek/.rvm/rubies/ruby-1.9.3-p385/bin/ruby
/Users/radek/.rvm/rubies/ruby-1.9.3-p385/lib/ruby/1.9.1/mkmf.rb:381:in `try_do': The compiler failed to generate an executable file. (RuntimeError)
You have to install development tools first.
from /Users/radek/.rvm/rubies/ruby-1.9.3-p385/lib/ruby/1.9.1/mkmf.rb:506:in `try_cpp'
from /Users/radek/.rvm/rubies/ruby-1.9.3-p385/lib/ruby/1.9.1/mkmf.rb:931:in `block in have_header'
from /Users/radek/.rvm/rubies/ruby-1.9.3-p385/lib/ruby/1.9.1/mkmf.rb:790:in `block in checking_for'
from /Users/radek/.rvm/rubies/ruby-1.9.3-p385/lib/ruby/1.9.1/mkmf.rb:284:in `block (2 levels) in postpone'
from /Users/radek/.rvm/rubies/ruby-1.9.3-p385/lib/ruby/1.9.1/mkmf.rb:254:in `open'
from /Users/radek/.rvm/rubies/ruby-1.9.3-p385/lib/ruby/1.9.1/mkmf.rb:284:in `block in postpone'
from /Users/radek/.rvm/rubies/ruby-1.9.3-p385/lib/ruby/1.9.1/mkmf.rb:254:in `open'
from /Users/radek/.rvm/rubies/ruby-1.9.3-p385/lib/ruby/1.9.1/mkmf.rb:280:in `postpone'
from /Users/radek/.rvm/rubies/ruby-1.9.3-p385/lib/ruby/1.9.1/mkmf.rb:789:in `checking_for'
from /Users/radek/.rvm/rubies/ruby-1.9.3-p385/lib/ruby/1.9.1/mkmf.rb:930:in `have_header'
from extconf.rb:9:in `<main>'
Gem files will remain installed in /Users/radek/.rvm/gems/ruby-1.9.3-p385/gems/mysql2-0.3.16 for inspection.
Results logged to /Users/radek/.rvm/gems/ruby-1.9.3-p385/gems/mysql2-0.3.16/ext/mysql2/gem_make.out
An error occurred while installing mysql2 (0.3.16), and Bundler cannot continue.
Make sure that `gem install mysql2 -v '0.3.16'` succeeds before bundling.
Thank you

Answer 1

On Ubuntu, run
sudo apt-get install libmysqlclient-dev
Or, if you use MariaDB, run
sudo apt-get install libmariadbclient-dev

Answer 2

Looks like there is no mysql2 gem installed in your machine.As you are using Mac OSX,you should be installing mysql2 gem like this
gem install mysql2 -- --with-mysql-dir=/usr/local/opt/mysql/
If the above command did't work,try like this
sudo gem install mysql -- --with-mysql-config=/usr/local/mysql/bin/mysql_config
And after try
bundle install
This should fix the error.
Source

Answer 3

Add this in Gemfile:-
gem 'mysql2', '0.3.16'
Then:-
bundle install
After that try:-
bundle update

Answer 4

I just installed mysql via $ brew install mysql and it fixed the problem.

Answer 5

I've ended up with a near-identical error message from attempting to build on a machine without gcc-c++ installed; mkmf is failing to compile a simple c program because the compiler flat out isn't there.
If you're on CentOS, you want sudo yum install gcc-c++. On Ubuntu, it's sudo apt-get install g++. It's a little disappointing that old versions of ruby-devel don't have a dependency on g++.