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rails--rails/activerecord/test/cases/attribute_test.rb
Sean Griffin be9b68038e Introduce ActiveRecord::Base#accessed_fields
This method can be used to see all of the fields on a model which have
been read. This can be useful during development mode to quickly find
out which fields need to be selected. For performance critical pages, if
you are not using all of the fields of a database, an easy performance
win is only selecting the fields which you need. By calling this method
at the end of a controller action, it's easy to determine which fields
need to be selected.

While writing this, I also noticed a place for an easy performance win
internally which I had been wanting to introduce. You cannot mutate a
field which you have not read. Therefore, we can skip the calculation of
in place changes if we have never read from the field. This can
significantly speed up methods like `#changed?` if any of the fields
have an expensive mutable type (like `serialize`)

```
Calculating -------------------------------------
 #changed? with serialized column (before)
                       391.000  i/100ms
 #changed? with serialized column (after)
                         1.514k i/100ms
-------------------------------------------------
 #changed? with serialized column (before)
                          4.243k (± 3.7%) i/s -     21.505k
 #changed? with serialized column (after)
                         16.789k (± 3.2%) i/s -     84.784k
```
2015-01-20 14:42:15 -07:00

192 lines
6.5 KiB
Ruby

require 'cases/helper'
require 'minitest/mock'
module ActiveRecord
class AttributeTest < ActiveRecord::TestCase
setup do
@type = Minitest::Mock.new
@type.expect(:==, false, [false])
end
teardown do
assert @type.verify
end
test "from_database + read type casts from database" do
@type.expect(:type_cast_from_database, 'type cast from database', ['a value'])
attribute = Attribute.from_database(nil, 'a value', @type)
type_cast_value = attribute.value
assert_equal 'type cast from database', type_cast_value
end
test "from_user + read type casts from user" do
@type.expect(:type_cast_from_user, 'type cast from user', ['a value'])
attribute = Attribute.from_user(nil, 'a value', @type)
type_cast_value = attribute.value
assert_equal 'type cast from user', type_cast_value
end
test "reading memoizes the value" do
@type.expect(:type_cast_from_database, 'from the database', ['whatever'])
attribute = Attribute.from_database(nil, 'whatever', @type)
type_cast_value = attribute.value
second_read = attribute.value
assert_equal 'from the database', type_cast_value
assert_same type_cast_value, second_read
end
test "reading memoizes falsy values" do
@type.expect(:type_cast_from_database, false, ['whatever'])
attribute = Attribute.from_database(nil, 'whatever', @type)
attribute.value
attribute.value
end
test "read_before_typecast returns the given value" do
attribute = Attribute.from_database(nil, 'raw value', @type)
raw_value = attribute.value_before_type_cast
assert_equal 'raw value', raw_value
end
test "from_database + read_for_database type casts to and from database" do
@type.expect(:type_cast_from_database, 'read from database', ['whatever'])
@type.expect(:type_cast_for_database, 'ready for database', ['read from database'])
attribute = Attribute.from_database(nil, 'whatever', @type)
type_cast_for_database = attribute.value_for_database
assert_equal 'ready for database', type_cast_for_database
end
test "from_user + read_for_database type casts from the user to the database" do
@type.expect(:type_cast_from_user, 'read from user', ['whatever'])
@type.expect(:type_cast_for_database, 'ready for database', ['read from user'])
attribute = Attribute.from_user(nil, 'whatever', @type)
type_cast_for_database = attribute.value_for_database
assert_equal 'ready for database', type_cast_for_database
end
test "duping dups the value" do
@type.expect(:type_cast_from_database, 'type cast', ['a value'])
attribute = Attribute.from_database(nil, 'a value', @type)
value_from_orig = attribute.value
value_from_clone = attribute.dup.value
value_from_orig << ' foo'
assert_equal 'type cast foo', value_from_orig
assert_equal 'type cast', value_from_clone
end
test "duping does not dup the value if it is not dupable" do
@type.expect(:type_cast_from_database, false, ['a value'])
attribute = Attribute.from_database(nil, 'a value', @type)
assert_same attribute.value, attribute.dup.value
end
test "duping does not eagerly type cast if we have not yet type cast" do
attribute = Attribute.from_database(nil, 'a value', @type)
attribute.dup
end
class MyType
def type_cast_from_user(value)
value + " from user"
end
def type_cast_from_database(value)
value + " from database"
end
end
test "with_value_from_user returns a new attribute with the value from the user" do
old = Attribute.from_database(nil, "old", MyType.new)
new = old.with_value_from_user("new")
assert_equal "old from database", old.value
assert_equal "new from user", new.value
end
test "with_value_from_database returns a new attribute with the value from the database" do
old = Attribute.from_user(nil, "old", MyType.new)
new = old.with_value_from_database("new")
assert_equal "old from user", old.value
assert_equal "new from database", new.value
end
test "uninitialized attributes yield their name if a block is given to value" do
block = proc { |name| name.to_s + "!" }
foo = Attribute.uninitialized(:foo, nil)
bar = Attribute.uninitialized(:bar, nil)
assert_equal "foo!", foo.value(&block)
assert_equal "bar!", bar.value(&block)
end
test "uninitialized attributes have no value" do
assert_nil Attribute.uninitialized(:foo, nil).value
end
test "attributes equal other attributes with the same constructor arguments" do
first = Attribute.from_database(:foo, 1, Type::Integer.new)
second = Attribute.from_database(:foo, 1, Type::Integer.new)
assert_equal first, second
end
test "attributes do not equal attributes with different names" do
first = Attribute.from_database(:foo, 1, Type::Integer.new)
second = Attribute.from_database(:bar, 1, Type::Integer.new)
assert_not_equal first, second
end
test "attributes do not equal attributes with different types" do
first = Attribute.from_database(:foo, 1, Type::Integer.new)
second = Attribute.from_database(:foo, 1, Type::Float.new)
assert_not_equal first, second
end
test "attributes do not equal attributes with different values" do
first = Attribute.from_database(:foo, 1, Type::Integer.new)
second = Attribute.from_database(:foo, 2, Type::Integer.new)
assert_not_equal first, second
end
test "attributes do not equal attributes of other classes" do
first = Attribute.from_database(:foo, 1, Type::Integer.new)
second = Attribute.from_user(:foo, 1, Type::Integer.new)
assert_not_equal first, second
end
test "an attribute has not been read by default" do
attribute = Attribute.from_database(:foo, 1, Type::Value.new)
assert_not attribute.has_been_read?
end
test "an attribute has been read when its value is calculated" do
attribute = Attribute.from_database(:foo, 1, Type::Value.new)
attribute.value
assert attribute.has_been_read?
end
test "an attribute can not be mutated if it has not been read,
and skips expensive calculations" do
type_which_raises_from_all_methods = Object.new
attribute = Attribute.from_database(:foo, "bar", type_which_raises_from_all_methods)
assert_not attribute.changed_in_place_from?("bar")
end
end
end