Merge pull request rails#54184 from Shopify/limit-number-of-returning-columns-after-insert-to-1-when-not-supported

Fix inserts on MySQL with no `RETURNING` support for a table with multiple auto populated columns

Author: byroot

activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb

@@ -174,6 +174,10 @@ def supports_insert_returning?
         mariadb? && database_version >= "10.5.0"
       end
 
+      def return_value_after_insert?(column) # :nodoc:
+        supports_insert_returning? ? column.auto_populated? : column.auto_increment?
+      end
+
       def get_advisory_lock(lock_name, timeout = 0) # :nodoc:
         query_value("SELECT GET_LOCK(#{quote(lock_name.to_s)}, #{timeout})") == 1
       end

activerecord/test/cases/persistence_test.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require "cases/helper"
+require "models/auto_id"
 require "models/aircraft"
 require "models/dashboard"
 require "models/clothing_item"
@@ -38,6 +39,22 @@ def test_populates_non_primary_key_autoincremented_column
     assert_not_nil topic.attributes["id"]
   end
 
+  def test_populates_autoincremented_id_pk_regardless_of_its_position_in_columns_list
+    auto_populated_column_names = AutoId.columns.select(&:auto_populated?).map(&:name)
+
+    # It's important we test a scenario where tables has more than one auto populated column
+    # and the first column is not the primary key. Otherwise it will be a regular test not asserting this special case.
+    assert auto_populated_column_names.size > 1
+    assert_not_equal AutoId.primary_key, auto_populated_column_names.first
+
+    record = AutoId.create!
+    last_id = AutoId.last.id
+
+    assert_not_nil last_id
+    assert last_id > 0
+    assert_equal last_id, record.id
+  end
+
   def test_populates_non_primary_key_autoincremented_column_for_a_cpk_model
     order = Cpk::Order.create(shop_id: 111_222)
 

activerecord/test/schema/schema.rb

@@ -105,8 +105,9 @@
   end
 
   create_table :auto_id_tests, force: true, id: false do |t|
-    t.primary_key :auto_id
     t.integer     :value
+    t.timestamp   :published_at, default: -> { "CURRENT_TIMESTAMP" }
+    t.primary_key :auto_id
   end
 
   create_table :binaries, force: true do |t|