Always return decimal average of integer fields

[rsim]

In previous version if database adapter (e.g. SQLite and Oracle) returned non-String calculated values then type_cast_using_column converted decimal average value of intefer field to integer value. Now operation parameter is always checked to decide which conversion of calculated value should be done.

This is fix for Lighthouse issue #6103
https://rails.lighthouseapp.com/projects/8994-ruby-on-rails/tickets/6103-average-returns-integer-values-instead-of-decimals
and is fixing bug that was introduced by commit 0a8eaff

This should be applied to master branch as well.

[tenderlove]

This breaks the mysql2 tests:

  1) Error:
test_average_with_from_option(CalculationsTest):
NoMethodError: undefined method `to_d' for #<BigDecimal:104c80690,'0.53E2',9(18)>
    /Users/apatterson/git/rails/activerecord/lib/active_record/relation/calculations.rb:279:in `type_cast_calculated_value'
    /Users/apatterson/git/rails/activerecord/lib/active_record/relation/calculations.rb:207:in `execute_simple_calculation'
    /Users/apatterson/git/rails/activerecord/lib/active_record/relation/calculations.rb:182:in `perform_calculation'
    /Users/apatterson/git/rails/activerecord/lib/active_record/relation/calculations.rb:152:in `calculate'
    /Users/apatterson/git/rails/activerecord/lib/active_record/relation/calculations.rb:66:in `average'
    /Users/apatterson/git/rails/activerecord/lib/active_record/base.rb:442:in `average'
    test/cases/calculations_test.rb:339:in `test_average_with_from_option'
    /Users/apatterson/.local/lib/ruby/gems/1.9.1/gems/mocha-0.9.10/lib/mocha/integration/mini_test/version_142_and_above.rb:27:in `run'
    /Users/apatterson/git/rails/activesupport/lib/active_support/testing/setup_and_teardown.rb:35:in `block in run'
    /Users/apatterson/git/rails/activesupport/lib/active_support/callbacks.rb:418:in `_run_setup_callbacks'
    /Users/apatterson/git/rails/activesupport/lib/active_support/testing/setup_and_teardown.rb:34:in `run'

  2) Error:
test_should_average_field(CalculationsTest):
NoMethodError: undefined method `to_d' for #<BigDecimal:106020448,'0.53E2',9(18)>
    /Users/apatterson/git/rails/activerecord/lib/active_record/relation/calculations.rb:279:in `type_cast_calculated_value'
    /Users/apatterson/git/rails/activerecord/lib/active_record/relation/calculations.rb:207:in `execute_simple_calculation'
    /Users/apatterson/git/rails/activerecord/lib/active_record/relation/calculations.rb:182:in `perform_calculation'
    /Users/apatterson/git/rails/activerecord/lib/active_record/relation/calculations.rb:152:in `calculate'
    /Users/apatterson/git/rails/activerecord/lib/active_record/relation/calculations.rb:66:in `average'
    /Users/apatterson/git/rails/activerecord/lib/active_record/base.rb:442:in `average'
    test/cases/calculations_test.rb:22:in `test_should_average_field'
    /Users/apatterson/.local/lib/ruby/gems/1.9.1/gems/mocha-0.9.10/lib/mocha/integration/mini_test/version_142_and_above.rb:27:in `run'
    /Users/apatterson/git/rails/activesupport/lib/active_support/testing/setup_and_teardown.rb:35:in `block in run'
    /Users/apatterson/git/rails/activesupport/lib/active_support/callbacks.rb:418:in `_run_setup_callbacks'
    /Users/apatterson/git/rails/activesupport/lib/active_support/testing/setup_and_teardown.rb:34:in `run'

  3) Error:
test_should_return_decimal_average_of_integer_field(CalculationsTest):
NoMethodError: undefined method `to_d' for #<BigDecimal:10499c578,'0.35E1',18(18)>
    /Users/apatterson/git/rails/activerecord/lib/active_record/relation/calculations.rb:279:in `type_cast_calculated_value'
    /Users/apatterson/git/rails/activerecord/lib/active_record/relation/calculations.rb:207:in `execute_simple_calculation'
    /Users/apatterson/git/rails/activerecord/lib/active_record/relation/calculations.rb:182:in `perform_calculation'
    /Users/apatterson/git/rails/activerecord/lib/active_record/relation/calculations.rb:152:in `calculate'
    /Users/apatterson/git/rails/activerecord/lib/active_record/relation/calculations.rb:66:in `average'
    /Users/apatterson/git/rails/activerecord/lib/active_record/base.rb:442:in `average'
    test/cases/calculations_test.rb:27:in `test_should_return_decimal_average_of_integer_field'
    /Users/apatterson/.local/lib/ruby/gems/1.9.1/gems/mocha-0.9.10/lib/mocha/integration/mini_test/version_142_and_above.rb:27:in `run'
    /Users/apatterson/git/rails/activesupport/lib/active_support/testing/setup_and_teardown.rb:35:in `block in run'
    /Users/apatterson/git/rails/activesupport/lib/active_support/callbacks.rb:418:in `_run_setup_callbacks'
    /Users/apatterson/git/rails/activesupport/lib/active_support/testing/setup_and_teardown.rb:34:in `run'

  4) Error:
test_delegates_finds_and_calculations_to_the_base_class(NamedScopeTest):
NoMethodError: undefined method `to_d' for #<BigDecimal:104903a58,'0.5E0',9(18)>
    /Users/apatterson/git/rails/activerecord/lib/active_record/relation/calculations.rb:279:in `type_cast_calculated_value'
    /Users/apatterson/git/rails/activerecord/lib/active_record/relation/calculations.rb:207:in `execute_simple_calculation'
    /Users/apatterson/git/rails/activerecord/lib/active_record/relation/calculations.rb:182:in `perform_calculation'
    /Users/apatterson/git/rails/activerecord/lib/active_record/relation/calculations.rb:152:in `calculate'
    /Users/apatterson/git/rails/activerecord/lib/active_record/relation/calculations.rb:66:in `average'
    /Users/apatterson/git/rails/activerecord/lib/active_record/base.rb:442:in `average'
    test/cases/named_scope_test.rb:47:in `test_delegates_finds_and_calculations_to_the_base_class'
    /Users/apatterson/.local/lib/ruby/gems/1.9.1/gems/mocha-0.9.10/lib/mocha/integration/mini_test/version_142_and_above.rb:27:in `run'
    /Users/apatterson/git/rails/activesupport/lib/active_support/testing/setup_and_teardown.rb:35:in `block in run'
    /Users/apatterson/git/rails/activesupport/lib/active_support/callbacks.rb:418:in `_run_setup_callbacks'
    /Users/apatterson/git/rails/activesupport/lib/active_support/testing/setup_and_teardown.rb:34:in `run'

2433 tests, 7757 assertions, 0 failures, 4 errors, 0 skips

[tenderlove]

Closing this since it's in master