Clean up module usage. There's no need to use InstanceMethods -- normal Ruby modules and includes will work fine here.

lib/activerecord-import/active_record/adapters/mysql2_adapter.rb

@@ -2,5 +2,5 @@ require "active_record/connection_adapters/mysql2_adapter"
 require "activerecord-import/adapters/mysql_adapter"
 
 class ActiveRecord::ConnectionAdapters::Mysql2Adapter
-  include ActiveRecord::Import::MysqlAdapter::InstanceMethods
-end
+  include ActiveRecord::Import::MysqlAdapter
+end

lib/activerecord-import/active_record/adapters/mysql_adapter.rb

@@ -2,5 +2,5 @@ require "active_record/connection_adapters/mysql_adapter"
 require "activerecord-import/adapters/mysql_adapter"
 
 class ActiveRecord::ConnectionAdapters::MysqlAdapter
-  include ActiveRecord::Import::MysqlAdapter::InstanceMethods
-end
+  include ActiveRecord::Import::MysqlAdapter
+end

lib/activerecord-import/active_record/adapters/postgresql_adapter.rb

@@ -2,6 +2,6 @@ require "active_record/connection_adapters/postgresql_adapter"
 require "activerecord-import/adapters/postgresql_adapter"
 
 class ActiveRecord::ConnectionAdapters::PostgreSQLAdapter
-  include ActiveRecord::Import::PostgreSQLAdapter::InstanceMethods
+  include ActiveRecord::Import::PostgreSQLAdapter
 end
 

lib/activerecord-import/active_record/adapters/sqlite3_adapter.rb

@@ -2,6 +2,6 @@ require "active_record/connection_adapters/sqlite3_adapter"
 require "activerecord-import/adapters/sqlite3_adapter"
 
 class ActiveRecord::ConnectionAdapters::Sqlite3Adapter
-  include ActiveRecord::Import::Sqlite3Adapter::InstanceMethods
+  include ActiveRecord::Import::Sqlite3Adapter
 end
 

lib/activerecord-import/adapters/mysql_adapter.rb

@@ -1,59 +1,53 @@
 module ActiveRecord::Import::MysqlAdapter
-  module InstanceMethods
-    def self.included(klass)
-      klass.instance_eval do
-        include ActiveRecord::Import::ImportSupport  
-        include ActiveRecord::Import::OnDuplicateKeyUpdateSupport
-      end
-    end
-    
-    # Returns the maximum number of bytes that the server will allow
-    # in a single packet
-    def max_allowed_packet # :nodoc:
-      result = execute( "SHOW VARIABLES like 'max_allowed_packet';" )
-      # original Mysql gem responds to #fetch_row while Mysql2 responds to #first
-      val = result.respond_to?(:fetch_row) ? result.fetch_row[1] : result.first[1]
-      val.to_i
-    end
-    
-    # Returns a generated ON DUPLICATE KEY UPDATE statement given the passed
-    # in +args+. 
-    def sql_for_on_duplicate_key_update( table_name, *args ) # :nodoc:
-      sql = ' ON DUPLICATE KEY UPDATE '
-      arg = args.first
-      if arg.is_a?( Array )
-        sql << sql_for_on_duplicate_key_update_as_array( table_name, arg )
-      elsif arg.is_a?( Hash )
-        sql << sql_for_on_duplicate_key_update_as_hash( table_name, arg )
-      elsif arg.is_a?( String )
-        sql << arg
-      else
-        raise ArgumentError.new( "Expected Array or Hash" )
-      end
-      sql
-    end
+  include ActiveRecord::Import::ImportSupport  
+  include ActiveRecord::Import::OnDuplicateKeyUpdateSupport
 
-    def sql_for_on_duplicate_key_update_as_array( table_name, arr )  # :nodoc:
-      results = arr.map do |column|
-        qc = quote_column_name( column )
-        "#{table_name}.#{qc}=VALUES(#{qc})"        
-      end
-      results.join( ',' )
-    end
-  
-    def sql_for_on_duplicate_key_update_as_hash( table_name, hsh ) # :nodoc:
-      sql = ' ON DUPLICATE KEY UPDATE '
-      results = hsh.map do |column1, column2|
-        qc1 = quote_column_name( column1 )
-        qc2 = quote_column_name( column2 )
-        "#{table_name}.#{qc1}=VALUES( #{qc2} )"
-      end
-      results.join( ',')
-    end
-
-    #return true if the statement is a duplicate key record error
-    def duplicate_key_update_error?(exception)# :nodoc:
-      exception.is_a?(ActiveRecord::StatementInvalid) && exception.to_s.include?('Duplicate entry')
-    end
+  # Returns the maximum number of bytes that the server will allow
+  # in a single packet
+  def max_allowed_packet # :nodoc:
+    result = execute( "SHOW VARIABLES like 'max_allowed_packet';" )
+    # original Mysql gem responds to #fetch_row while Mysql2 responds to #first
+    val = result.respond_to?(:fetch_row) ? result.fetch_row[1] : result.first[1]
+    val.to_i
   end
-end
+  
+  # Returns a generated ON DUPLICATE KEY UPDATE statement given the passed
+  # in +args+. 
+  def sql_for_on_duplicate_key_update( table_name, *args ) # :nodoc:
+    sql = ' ON DUPLICATE KEY UPDATE '
+    arg = args.first
+    if arg.is_a?( Array )
+      sql << sql_for_on_duplicate_key_update_as_array( table_name, arg )
+    elsif arg.is_a?( Hash )
+      sql << sql_for_on_duplicate_key_update_as_hash( table_name, arg )
+    elsif arg.is_a?( String )
+      sql << arg
+    else
+      raise ArgumentError.new( "Expected Array or Hash" )
+    end
+    sql
+  end
+
+  def sql_for_on_duplicate_key_update_as_array( table_name, arr )  # :nodoc:
+    results = arr.map do |column|
+      qc = quote_column_name( column )
+      "#{table_name}.#{qc}=VALUES(#{qc})"
+    end
+    results.join( ',' )
+  end
+
+  def sql_for_on_duplicate_key_update_as_hash( table_name, hsh ) # :nodoc:
+    sql = ' ON DUPLICATE KEY UPDATE '
+    results = hsh.map do |column1, column2|
+      qc1 = quote_column_name( column1 )
+      qc2 = quote_column_name( column2 )
+      "#{table_name}.#{qc1}=VALUES( #{qc2} )"
+    end
+    results.join( ',')
+  end
+
+  #return true if the statement is a duplicate key record error
+  def duplicate_key_update_error?(exception)# :nodoc:
+    exception.is_a?(ActiveRecord::StatementInvalid) && exception.to_s.include?('Duplicate entry')
+  end
+end

lib/activerecord-import/adapters/postgresql_adapter.rb

@@ -1,13 +1,7 @@
 module ActiveRecord::Import::PostgreSQLAdapter
-  module InstanceMethods
-    def self.included(klass)
-      klass.instance_eval do
-        include ActiveRecord::Import::ImportSupport
-      end
-    end
+  include ActiveRecord::Import::ImportSupport
 
-    def next_value_for_sequence(sequence_name)
-      %{nextval('#{sequence_name}')}
-    end
+  def next_value_for_sequence(sequence_name)
+    %{nextval('#{sequence_name}')}
   end
 end

lib/activerecord-import/adapters/sqlite3_adapter.rb

@@ -1,7 +1,5 @@
 module ActiveRecord::Import::Sqlite3Adapter
-  module InstanceMethods
-    def next_value_for_sequence(sequence_name)
-      %{nextval('#{sequence_name}')}
-    end
+  def next_value_for_sequence(sequence_name)
+    %{nextval('#{sequence_name}')}
   end
 end