Even faster for postgresql

lib/delayed/backend/active_record.rb

@@ -68,17 +68,19 @@ def self.reserve(worker, max_run_time = Worker.max_run_time)
 
           now = self.db_time_now
 
-          # This works on any database and uses seperate queries to lock and return the job
-          # Databases like PostgreSQL and MySQL that support "SELECT .. FOR UPDATE" (ActiveRecord Pessimistic locking) don't need the second application
-          # of 'readyScope' but it doesn't hurt and it ensures that the job being locked still meets ready_to_run criteria. 
-          count = readyScope.where(:id => nextScope).update_all(:locked_at => now, :locked_by => worker.name)
-          return nil if count == 0
-          return self.where(:locked_at => now, :locked_by => worker.name).first
-
-          # This works on PostgreSQL and uses 1 less query, but uses SQL not supported nativly through ActiveRecord
-          #quotedTableName = ::ActiveRecord::Base.connection.quote_column_name(self.table_name)
-          #reserved = self.find_by_sql(["UPDATE #{quotedTableName} SET locked_at = ?, locked_by = ? WHERE id IN (#{nextScope.to_sql}) RETURNING *",now,worker.name])
-          #return reserved[0]
+          if rails3? && (::ActiveRecord::Base.connection.adapter_name == "PostgreSQL")
+            # This works on PostgreSQL and uses 1 less query, but uses SQL not supported nativly through ActiveRecord
+            quotedTableName = ::ActiveRecord::Base.connection.quote_column_name(self.table_name)
+            reserved = self.find_by_sql(["UPDATE #{quotedTableName} SET locked_at = ?, locked_by = ? WHERE id IN (#{nextScope.to_sql}) RETURNING *",now,worker.name])
+            return reserved[0]
+          else
+            # This works on any database and uses seperate queries to lock and return the job
+            # Databases like PostgreSQL and MySQL that support "SELECT .. FOR UPDATE" (ActiveRecord Pessimistic locking) don't need the second application
+            # of 'readyScope' but it doesn't hurt and it ensures that the job being locked still meets ready_to_run criteria. 
+            count = readyScope.where(:id => nextScope).update_all(:locked_at => now, :locked_by => worker.name)
+            return nil if count == 0
+            return self.where(:locked_at => now, :locked_by => worker.name).first
+          end
         end
 
         # Lock this job for this worker.