Relation#ids answers a uuid key as its leading digits (.to_i on every key) #310

Probed at main a643ac7 (the runtime is unchanged at bc4acba), Linux x86-64, gcc 16.2.1 (Spinel 01d9d2f02).

Relation#ids answers the primary keys of a uuid-keyed model as Integers: the runtime reads #{@table}.id and calls .to_i on each value, and the sidecar seeds it Array[Integer]. So a uuid 44444444-4444-4444-8444-444444444441 comes back as 44444444, and a key starting with a letter as 0. The neighbours already carry string keys since #90 and #266: find casts through _cast_primary_key, the model's own finders take its key type, and pluck(:id) answers the stored value.

db/schema.rb:

ActiveRecord::Schema[8.1].define(version: 2026_01_01_000000) do
  create_table "widgets", id: :uuid, force: :cascade do |t|
    t.string "name"
    t.boolean "active", default: true
  end
end

app/controllers/widgets_controller.rb:

class WidgetsController < ApplicationController
  def index
    render plain: Widget.count.to_s
  end

  def exists
    render plain: Widget.where(active: true).exists?(params[:id]).to_s
  end

  def ids
    render plain: Widget.where(active: true).ids.join(",")
  end
end

(config/routes.rb: root "widgets#index", get "widgets/:id/exists", to: "widgets#exists", get "widget_ids", to: "widgets#ids"; Widget < ApplicationRecord with no body.)

With one row, id = '44444444-4444-4444-8444-444444444441', after spin build:

The runtime, runtime/ruby/active_record/relation.rb:

    # `ids` — primary keys, as integers.
    def ids
      prior = @select_sql
      @select_sql = "#{@table}.id AS v"
      rows = ActiveRecord.adapter.select_rows(to_sql)
      @select_sql = prior
      rows.map { |row| row["v"].to_i }
    end

A model with self.primary_key = "identifier" would read the wrong column as well (I read that from the code rather than ran it).

A possible shape: select @model.primary_key and map each value through @model._cast_primary_key (as find does), with the ids seed widened for string-keyed apps the way widen_key_contract widens id. I have not tried that against the integer-keyed corpus, where the narrower Array[Integer] may matter to the typing, so I'm leaving the approach to you.

Found while compiling a Rails API app with --target spinel.