Company.find_in_batches(:batch_size => 100, :conditions => "reviewed_state != 's'") {|coms| p coms.size }

 Company Load (10.5ms)  SELECT "companies".* FROM "companies" WHERE (reviewed_state != 's') ORDER BY "companies"."id" ASC LIMIT 100
100
  Company Load (8.2ms)  SELECT "companies".* FROM "companies" WHERE (reviewed_state != 's') AND ("companies"."id" > 2143) ORDER BY "companies"."id" ASC LIMIT 100
100
  Company Load (6.2ms)  SELECT "companies".* FROM "companies" WHERE (reviewed_state != 's') AND ("companies"."id" > 2243) ORDER BY "companies"."id" ASC LIMIT 100
100
  Company Load (4.4ms)  SELECT "companies".* FROM "companies" WHERE (reviewed_state != 's') AND ("companies"."id" > 2343) ORDER BY "companies"."id" ASC LIMIT 100
44
 => nil 

Company.find_each(:batch_size => 5, :start => 350) {|v| p v.name}