From: "tenderlovemaking (Aaron Patterson) via ruby-core" <ruby-core@...>
Date: 2025-10-29T19:44:13+00:00
Subject: [ruby-core:123603] [Ruby Bug#21654] Set#new calls extra methods compared to previous versions

Issue #21654 has been updated by tenderlovemaking (Aaron Patterson).


mame (Yusuke Endoh) wrote in #note-5:
> >���How about handling only `Range` and `Enumerator` (not `Enumerable`) for now?
> 
> I think it would be better to handle only Range for now, and not Enumerator either. See https://bugs.ruby-lang.org/issues/21513#note-10

I sent a pull request that only handles `Range` for now:  https://github.com/ruby/ruby/pull/14990

This fixes the issues we're seeing in tests.

----------------------------------------
Bug #21654: Set#new calls extra methods compared to previous versions
https://bugs.ruby-lang.org/issues/21654#change-114985

* Author: tenderlovemaking (Aaron Patterson)
* Status: Open
* ruby -v: ruby 3.5.0dev (2025-10-24T15:50:47Z master a9f24aaccb) +PRISM [arm64-darwin25]
* Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
----------------------------------------
I'm trying to test Ruby 3.5.0 with our Rails application and we've found that `Set.new` is now causing extra database queries to happen.

The changes in d4020dd5faf call "size" on enumerable objects that are passed to the `new` method, and this causes extra "COUNT" queries to happen with ActiveRecord associations.

For example:

```ruby
Set.new(some_activerecord_association)
```

Previously, the above code would only do one query by iterating over the association. Now it issues two queries, a count query, and then the normal query for results.

Since d4020dd5faf is dealing with endless ranges, I would like to narrow the scope from all Enumerable objects to just Ranges.  Unfortunately, I noticed we have a test like this:

```ruby
    assert_raise(ArgumentError) {
      Set.new(1.upto(Float::INFINITY))
    }
```

I'm not sure how we can handle such a case without testing `size`.



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