Backport to older version of ActiveRecord

delayed_job_active_record.gemspec

@@ -15,7 +15,7 @@ Gem::Specification.new do |s|
   s.require_paths     = ["lib"]
   s.test_files        = Dir.glob('spec/**/*')
 
-  s.add_runtime_dependency      'activerecord',  '~> 3.0'
+  s.add_runtime_dependency      'activerecord',  '> 2.1.0'
   s.add_runtime_dependency      'delayed_job',   '3.0.0.pre'
 
   s.add_development_dependency  'rspec',          '~> 2.0'

lib/delayed/backend/active_record.rb

@@ -1,3 +1,5 @@
+require 'active_record'
+require 'active_record/version'
 module Delayed
   module Backend
     module ActiveRecord
@@ -8,11 +10,22 @@ class Job < ::ActiveRecord::Base
         set_table_name :delayed_jobs
 
         before_save :set_default_run_at
-
-        scope :ready_to_run, lambda {|worker_name, max_run_time|
-          where(['(run_at <= ? AND (locked_at IS NULL OR locked_at < ?) OR locked_by = ?) AND failed_at IS NULL', db_time_now, db_time_now - max_run_time, worker_name])
-        }
-        scope :by_priority, order('priority ASC, run_at ASC')
+
+        def self.rails3?
+          ::ActiveRecord::VERSION::MAJOR == 3
+        end
+
+        if rails3?
+          scope :ready_to_run, lambda{|worker_name, max_run_time|
+            where('(run_at <= ? AND (locked_at IS NULL OR locked_at < ?) OR locked_by = ?) AND failed_at IS NULL', db_time_now, db_time_now - max_run_time, worker_name)
+          }
+          scope :by_priority, order('priority ASC, run_at ASC')
+        else
+          named_scope :ready_to_run, lambda {|worker_name, max_run_time|
+            { :conditions => ['(run_at <= ? AND (locked_at IS NULL OR locked_at < ?) OR locked_by = ?) AND failed_at IS NULL', db_time_now, db_time_now - max_run_time, worker_name] }
+          }
+          named_scope :by_priority, :order => 'priority ASC, run_at ASC'
+        end
 
         def self.before_fork
           ::ActiveRecord::Base.clear_all_connections!