Error building PostgreSQL gem with `budle install` [Ubuntu 10.04, Ruby EE]

I've Ruby Enterprise Edition installed on Ubuntu 10.04 as the default Ruby interpreter:

ruby 1.8.7 (2010-12-23 patchlevel 330) [i686-linux], MBARI 0x8770, Ruby Enterprise Edition 2011.01

If I sudo gem install pg, the gem is installed successfully.

But withing my Rails app, bundle install hangs up like that:

[...]
Using net-sftp (2.0.5) 
Using net-ssh-gateway (1.0.1) 
Using capistrano (2.5.19) 
Installing pg (0.10.1) with native extensions /opt/ruby-enterprise-1.8.7-2011.01/lib/ruby/site_ruby/1.8/rubygems/installer.rb:529:in `build_extensions': ERROR: Failed to build gem native extension. (Gem::Installer::ExtensionBuildError)

        /opt/ruby-enterprise-1.8.7-2011.01/bin/ruby extconf.rb 

Gem files will remain installed in /home/selhozka/rails/vendor/gems/ruby/1.8/gems/pg-0.10.1 for inspection.
Results logged to /home/selhozka/rails/vendor/gems/ruby/1.8/gems/pg-0.10.1/ext/gem_make.out
    from /opt/ruby-enterprise-1.8.7-2011.01/lib/ruby/site_ruby/1.8/rubygems/installer.rb:482:in `each'
    from /opt/ruby-enterprise-1.8.7-2011.01/lib/ruby/site_ruby/1.8/rubygems/installer.rb:482:in `build_extensions'
    from /opt/ruby-enterprise-1.8.7-2011.01/lib/ruby/site_ruby/1.8/rubygems/installer.rb:156:in `install'
    from /opt/ruby-enterprise-1.8.7-2011.01/lib/ruby/gems/1.8/gems/bundler-1.0.10/lib/bundler/source.rb:96:in `install'
    from /opt/ruby-enterprise-1.8.7-2011.01/lib/ruby/gems/1.8/gems/bundler-1.0.10/lib/bundler/installer.rb:55:in `run'
    from /opt/ruby-enterprise-1.8.7-2011.01/lib/ruby/gems/1.8/gems/bundler-1.0.10/lib/bundler/spec_set.rb:12:in `each'
    from /opt/ruby-enterprise-1.8.7-2011.01/lib/ruby/gems/1.8/gems/bundler-1.0.10/lib/bundler/spec_set.rb:12:in `each'
    from /opt/ruby-enterprise-1.8.7-2011.01/lib/ruby/gems/1.8/gems/bundler-1.0.10/lib/bundler/installer.rb:44:in `run'
    from /opt/ruby-enterprise-1.8.7-2011.01/lib/ruby/gems/1.8/gems/bundler-1.0.10/lib/bundler/installer.rb:8:in `install'
    from /opt/ruby-enterprise-1.8.7-2011.01/lib/ruby/gems/1.8/gems/bundler-1.0.10/lib/bundler/cli.rb:226:in `install'
    from /opt/ruby-enterprise-1.8.7-2011.01/lib/ruby/gems/1.8/gems/bundler-1.0.10/lib/bundler/vendor/thor/task.rb:22:in `send'
    from /opt/ruby-enterprise-1.8.7-2011.01/lib/ruby/gems/1.8/gems/bundler-1.0.10/lib/bundler/vendor/thor/task.rb:22:in `run'
    from /opt/ruby-enterprise-1.8.7-2011.01/lib/ruby/gems/1.8/gems/bundler-1.0.10/lib/bundler/vendor/thor/invocation.rb:118:in `invoke_task'
    from /opt/ruby-enterprise-1.8.7-2011.01/lib/ruby/gems/1.8/gems/bundler-1.0.10/lib/bundler/vendor/thor.rb:246:in `dispatch'
    from /opt/ruby-enterprise-1.8.7-2011.01/lib/ruby/gems/1.8/g开发者_JS百科ems/bundler-1.0.10/lib/bundler/vendor/thor/base.rb:389:in `start'
    from /opt/ruby-enterprise-1.8.7-2011.01/lib/ruby/gems/1.8/gems/bundler-1.0.10/bin/bundle:13
    from /opt/ruby-enterprise-1.8.7-2011.01/bin/bundle:19:in `load'
    from /opt/ruby-enterprise-1.8.7-2011.01/bin/bundle:19

The contents of /home/selhozka/rails/vendor/gems/ruby/1.8/gems/pg-0.10.1/ext/gem_make.out:

/opt/ruby-enterprise-1.8.7-2011.01/bin/ruby extconf.rb 

It was a lack-of-memory issue with an OpenVZ VPS.

There was only 256 MB of RAM and OpenVZ doesn't provide you with swap space. So the script hang up.