Reveert build_relations and simply add a line for creating iid

lib/gitlab/ci/pipeline/chain/populate.rb

@@ -8,7 +8,13 @@ module Gitlab
           PopulateError = Class.new(StandardError)
 
           def perform!
-            build_relations
+            # Allocate next IID. This operation must be outside of transactions of pipeline creations.
+            pipeline.ensure_project_iid!
+
+            ##
+            # Populate pipeline with block argument of CreatePipelineService#execute.
+            #
+            @command.seeds_block&.call(pipeline)
 
             ##
             # Populate pipeline with all stages, and stages with builds.
@@ -31,18 +37,6 @@ module Gitlab
           def break?
             pipeline.errors.any?
           end
-
-          private
-
-          def build_relations
-            ##
-            # Populate pipeline with block argument of CreatePipelineService#execute.
-            #
-            @command.seeds_block&.call(pipeline)
-
-            # Allocate next IID. This operation must be outside of transactions of pipeline creations.
-            pipeline.ensure_project_iid!
-          end
         end
       end
     end

spec/lib/gitlab/ci/pipeline/chain/populate_spec.rb

@@ -140,10 +140,10 @@ describe Gitlab::Ci::Pipeline::Chain::Populate do
         expect { step.perform! }.to raise_error(ActiveRecord::RecordNotSaved)
       end
 
-      it 'does not waste pipeline iid' do
-        step.perform rescue nil
+      it 'wastes pipeline iid' do
+        expect { step.perform! }.to raise_error
 
-        expect(InternalId.ci_pipelines.where(project_id: project.id).exists?).to be_falsy
+        expect(InternalId.ci_pipelines.where(project_id: project.id).exists?).to be_truthy
       end
     end
   end