Rails: postgres adapter returns string instead of integer

gistfile1.rb

ris  = RequestedItem.currently_requested.joins(:order_request).
  group(:item_variant_id).select('requested_items.*, order_request.business_site_id').all
ris.first[:business_site_id].class == String #instead of Fixnum...

#with SQLite with can:
if ris.first[:business_site_id]  ==  DEFAULT_SITE
  ..
#but with PG, we must:  
if ris.first[:business_site_id].try(:to_i)  ==  DEFAULT_SITE
  ..
  
#Another example:
RequestedItem.where(id: 1).select(*, 10 AS tq).first.tq.class   #   =>   String

# http://stackoverflow.com/questions/12571215/connection-select-value-only-returns-strings-in-postgres-with-pg-gem

#Tried with: Rails 3.0.20  with pg gem 0.17.1 and psql 9.3.5 on mac os x 10.8.5
#Same result with Rails 3.2.22 / pg gem 0.18.4

#Same setup with Rails > 4.0.10 return proper type...

[4] pry(main)> Simulation.joins(:factor_instances).select("simulations.*, factor_instances.value").first[:model_id]
  Simulation Load (0.9ms)  SELECT  simulations.*, factor_instances.value FROM "simulations" INNER JOIN "factor_instances" ON "factor_instances"."simulation_id" = "simulations"."id"  ORDER BY "simulations"."id" ASC LIMIT 1
=> 1
[5] pry(main)> Simulation.joins(:factor_instances).select("simulations.*, factor_instances.value").first[:model_id].class
  Simulation Load (0.7ms)  SELECT  simulations.*, factor_instances.value FROM "simulations" INNER JOIN "factor_instances" ON "factor_instances"."simulation_id" = "simulations"."id"  ORDER BY "simulations"."id" ASC LIMIT 1
=> Fixnum
[6] pry(main)> Simulation.joins(:factor_instances).select("simulations.*, factor_instances.value").first[:value].class
  Simulation Load (0.7ms)  SELECT  simulations.*, factor_instances.value FROM "simulations" INNER JOIN "factor_instances" ON "factor_instances"."simulation_id" = "simulations"."id"  ORDER BY "simulations"."id" ASC LIMIT 1
=> BigDecimal

What's your versions for PostgreSQL, pg gem and rails?