Move code behind feature flag

Puts the changes under the use_insert_all_in_internal_id feature flag

app/models/internal_id.rb

@@ -223,6 +223,7 @@ class InternalId < ApplicationRecord
     # If another process was faster in doing this, we'll end up with that record
     # when we do the lookup after the insert.
     def create_record
+      if Feature.enabled?(:use_insert_all_in_internal_id, default_enabled: :yaml)
         scope[:project].save! if scope[:project] && !scope[:project].persisted?
         scope[:namespace].save! if scope[:namespace] && !scope[:namespace].persisted?
 
@@ -235,9 +236,22 @@ class InternalId < ApplicationRecord
 
         InternalId.insert_all([attributes])
 
+        lookup
+      else
+        begin
+          subject.transaction(requires_new: true) do
+            InternalId.create!(
+              **scope,
+              usage: usage_value,
+              last_value: initial_value(subject, scope)
+            )
+          end
+        rescue ActiveRecord::RecordNotUnique
           lookup
         end
       end
+    end
+  end
 
   class ImplicitlyLockingInternalIdGenerator
     # Generate next internal id for a given scope and usage.
@@ -330,6 +344,7 @@ class InternalId < ApplicationRecord
     end
 
     def create_record!(subject, scope, usage, value)
+      if Feature.enabled?(:use_insert_all_in_internal_id, default_enabled: :yaml)
         scope[:project].save! if scope[:project] && !scope[:project].persisted?
         scope[:namespace].save! if scope[:namespace] && !scope[:namespace].persisted?
 
@@ -345,6 +360,16 @@ class InternalId < ApplicationRecord
         raise RecordAlreadyExists if result.empty?
 
         value
+      else
+        begin
+          subject.transaction(requires_new: true) do
+            internal_id = InternalId.create!(**scope, usage: usage, last_value: value)
+            internal_id.last_value
+          end
+        rescue ActiveRecord::RecordNotUnique
+          raise RecordAlreadyExists
+        end
+      end
     end
 
     def arel_table

config/feature_flags/development/use_insert_all_in_internal_id.yml

+---
+name: use_insert_all_in_internal_id
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/68617
+rollout_issue_url: 
+milestone: '14.3'
+type: development
+group: group::project management
+default_enabled: false

spec/models/internal_id_spec.rb

@@ -238,21 +238,49 @@ RSpec.describe InternalId do
     end
   end
 
-  context 'when the feature flag is disabled' do
+  context 'when the explicit locking feature flag is disabled' do
     before do
       stub_feature_flags(generate_iids_without_explicit_locking: false)
     end
 
+    context 'when the insert all feature flag is enabled' do
+      before do
+        stub_feature_flags(use_insert_all_in_internal_id: true)
+      end
+
+      it_behaves_like 'a monotonically increasing id generator'
+    end
+
+    context 'when the insert all feature flag is disabled' do
+      before do
+        stub_feature_flags(use_insert_all_in_internal_id: false)
+      end
+
       it_behaves_like 'a monotonically increasing id generator'
     end
+  end
 
-  context 'when the feature flag is enabled' do
+  context 'when the explicit locking feature flag is enabled' do
     before do
       stub_feature_flags(generate_iids_without_explicit_locking: true)
     end
 
+    context 'when the insert all feature flag is enabled' do
+      before do
+        stub_feature_flags(use_insert_all_in_internal_id: true)
+      end
+
+      it_behaves_like 'a monotonically increasing id generator'
+    end
+
+    context 'when the insert all feature flag is disabled' do
+      before do
+        stub_feature_flags(use_insert_all_in_internal_id: false)
+      end
+
       it_behaves_like 'a monotonically increasing id generator'
     end
+  end
 
   describe '#increment_and_save!' do
     let(:id) { create(:internal_id) }