About 85% through porting over MySQL on duplicate key functionality.

lib/ar-extensions/import/mysql.rb

@@ -0,0 +1,50 @@
+module ActiveRecord::Extensions::ConnectionAdapters::MysqlAdapter # :nodoc:
+
+  include ActiveRecord::Extensions::Import::ImportSupport  
+  include ActiveRecord::Extensions::Import::OnDuplicateKeyUpdateSupport
+    
+  # 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
+
+ActiveRecord::ConnectionAdapters::MysqlAdapter.class_eval do
+  include ActiveRecord::Extensions::ConnectionAdapters::MysqlAdapter
+end