title: ActiveRecord::ConnectionNotEstablished error (eager loading?)
body: <p>I'm developing on OSX and deploying on Linux. My environments are:</p>
  
  <p>Development:</p>
  
  <pre><code>OSX Lion
  Ruby 1.9.2p180
  ActiveRecord 3.0.9
  PostgreSQL 9.0
  </code></pre>
  
  <p>Test:</p>
  
  <pre><code>Ubuntu Server 11.04
  Ruby 1.9.2p290
  ActiveRecord 3.1.1
  PostgreSQL 9.1
  </code></pre>
  
  <p>The following pieces of code work on OSX but not on Linux:</p>
  
  <pre><code>ei_doc_type = TaxDoc::Model::DocType.find_by_doc_type("EI")
  doc_version = ei_doc_type.doc_versions.find_by_doc_version(edoc.version)
  customer.electronic_invoices.create(....)
  </code></pre>
  
  <p>and:</p>
  
  <pre><code>ei_doc_type = TaxDoc::Model::DocType.find_by_doc_type("EI")
  ei_doc_type.doc_versions.each { |doc_version|
    @mappings[doc_version.doc_version] = Hash.new
    doc_version.mappings.each { |mapping|
      @mappings[doc_version.doc_version][mapping.column_name] = mapping.xml_element
    }
  }
  </code></pre>
  
  <p>When I try to run any of these pieces of code in Linux I get the following error:</p>
  
  <pre><code>.../connection_pool.rb:409: in `retrieve_connection': ActiveRecord::ConnectionNotEstablished (ActiveRecord::ConnectionNotEstablished)
  </code></pre>
  
  <p>I changed the code, and it works on Linux:</p>
  
  <pre><code>ei_doc_type = TaxDoc::Model::DocType.find_by_doc_type("EI")
  doc_versions = TaxDoc::Model::DocVersion.where(:doc_type_id =&gt; ei_doc_type.id, :doc_version =&gt; edoc.version)
  doc_version = doc_version.first
  customer.electronic_invoices.create(....)
  </code></pre>
  
  <p>and:</p>
  
  <pre><code>ei_doc_type = TaxDoc::Model::DocType.includes(:doc_versions =&gt; :mappings).find_by_doc_type("EI")
  ei_doc_type.doc_versions.each { |doc_version|
    @mappings[doc_version.doc_version] = Hash.new
    doc_version.mappings.each { |mapping|
      @mappings[doc_version.doc_version][mapping.column_name] = mapping.xml_element
    }
  }
  </code></pre>
  
  <p>It seems like eager loading for first order associations is not working on the test environment, and in the first example. Even if I use "includes" it does not work.</p>
  
  <p>Is there a difference between versions on ActiveRecord or PostgreSQL that could be causing this?</p>
  
  <p>These are my models:</p>
  
  <pre><code>class DocType &lt; EDocsDatabase
    has_many :doc_versions, :dependent =&gt; :destroy
    has_many :mappings, :through =&gt; :doc_versions
    has_many :service_types
  end
  
  class DocVersion &lt; EDocsDatabase
    belongs_to :doc_type
    has_many :mappings, :dependent =&gt; :destroy
  end
  
  class Mapping &lt; EDocsDatabase
    belongs_to :doc_version
  end
  </code></pre>