PERF: Recover marshaling dump/load performance (#31827)

* PERF: Recover marshaling dump/load performance

This performance regression which is described in #30680 was caused by
f0ddf87 due to force materialized `LazyAttributeHash`.

Since 95b86e5, default proc has been removed in the class, so it is no
longer needed that force materialized.

Avoiding force materialized will recover marshaling dump/load
performance.

Benchmark:

https://gist.github.com/blimmer/1360ea51cd3147bae8aeb7c6d09bff17

Before:

```
it took 0.6248569069430232 seconds to unmarshal the objects

Total allocated: 38681544 bytes (530060 objects)

allocated memory by class
-----------------------------------
  12138848  Hash
  10542384  String
   7920000  ActiveModel::Attribute::Uninitialized
   5600000  ActiveModel::Attribute::FromDatabase
   1200000  Foo
    880000  ActiveModel::LazyAttributeHash
    400000  ActiveModel::AttributeSet
        80  Integer
        72  ActiveRecord::ConnectionAdapters::SQLite3Adapter::SQLite3Integer
        40  ActiveModel::Type::String
        40  ActiveRecord::Type::DateTime
        40  Object
        40  Range

allocated objects by class
-----------------------------------
    250052  String
    110000  ActiveModel::Attribute::Uninitialized
     70001  Hash
     70000  ActiveModel::Attribute::FromDatabase
     10000  ActiveModel::AttributeSet
     10000  ActiveModel::LazyAttributeHash
     10000  Foo
         2  Integer
         1  ActiveModel::Type::String
         1  ActiveRecord::ConnectionAdapters::SQLite3Adapter::SQLite3Integer
         1  ActiveRecord::Type::DateTime
         1  Object
         1  Range
```

After:

```
it took 0.1660824950085953 seconds to unmarshal the objects

Total allocated: 13883811 bytes (220090 objects)

allocated memory by class
-----------------------------------
   5743371  String
   4940008  Hash
   1200000  Foo
    880000  ActiveModel::LazyAttributeHash
    720000  Array
    400000  ActiveModel::AttributeSet
        80  ActiveModel::Attribute::FromDatabase
        80  Integer
        72  ActiveRecord::ConnectionAdapters::SQLite3Adapter::SQLite3Integer
        40  ActiveModel::Type::String
        40  ActiveModel::Type::Value
        40  ActiveRecord::Type::DateTime
        40  Object
        40  Range

allocated objects by class
-----------------------------------
    130077  String
     50004  Hash
     10000  ActiveModel::AttributeSet
     10000  ActiveModel::LazyAttributeHash
     10000  Array
     10000  Foo
         2  Integer
         1  ActiveModel::Attribute::FromDatabase
         1  ActiveModel::Type::String
         1  ActiveModel::Type::Value
         1  ActiveRecord::ConnectionAdapters::SQLite3Adapter::SQLite3Integer
         1  ActiveRecord::Type::DateTime
         1  Object
         1  Range
```

Fixes #30680.

* Keep the `@delegate_hash` to avoid to lose any mutations that have been made to the record

1 files changed, 16 insertions, 0 deletions

diff --git a/activemodel/test/cases/attribute_set_test.rb b/activemodel/test/cases/attribute_set_test.rb
index 9b323dae9d..b868dba743 100644
--- a/activemodel/test/cases/attribute_set_test.rb
+++ b/activemodel/test/cases/attribute_set_test.rb
@@ -217,6 +217,22 @@ module ActiveModel
       assert_equal({ foo: "1" }, attributes.to_hash)
     end
 
+    test "marshaling dump/load legacy materialized attribute hash" do
+      builder = AttributeSet::Builder.new(foo: Type::String.new)
+      attributes = builder.build_from_database(foo: "1")
+
+      attributes.instance_variable_get(:@attributes).instance_eval do
+        class << self
+          def marshal_dump
+            materialize
+          end
+        end
+      end
+
+      attributes = Marshal.load(Marshal.dump(attributes))
+      assert_equal({ foo: "1" }, attributes.to_hash)
+    end
+
     test "#accessed_attributes returns only attributes which have been read" do
       builder = AttributeSet::Builder.new(foo: Type::Value.new, bar: Type::Value.new)
       attributes = builder.build_from_database(foo: "1", bar: "2")