ActiveScaffold and LOB sorting in Oracle

If you are using ActiveScaffold and an Oracle DB, you will notice that you can't natively sort on LOB columns. If you click on the table header for a LOB column, you will get an error message. A way to fix this is to sort using the substr function and pass it to config.columns[].sort_by :sql.

To make it simpler, I solved the matter including in ActiveScaffold::DataStructures::Column a
method:

def sort_as_lob(lenght = 50, offset = 1)
  sort_by :sql => "dbms_lob.substr(#{name},"+
                                  "#{lenght},"+
                                  "#{offset})"
end

which I use on LOBs column declaring in the active scaffold config block:

active_scaffold do |config|
config.columns[:my_lob].sort_as_lob
end

oracle adapter and rails migrations

The Oracle adapter for active record has a bug that does not allow to create a dump of the schema using rake. The following code is from http://dev.rubyonrails.org/ticket/10415 and corrects this problem.

require 'active_record/connection_adapters/oracle_adapter'
module ActiveRecord
  module ConnectionAdapters
   class OracleAdapter
     # Returns an array of arrays containing the field values.
     # Order is the same as that returned by #columns.
     def select_rows(sql, name = nil)
       result = select(sql, name)
       result.map{ |v| v.values}
     end
   end
 end
end