Split same_family_pipeline_ids query to reduce complexity

Ci::Pipeline#same_family_pipeline_ids uses PipelineObjectHierarchy
to recursively find all pipelines (parent + children) given
a pipeline object.

This previously was finding recursively all ancestors and then
all descendants. We can instead fire two queries, one to find
the root ancestor and then use that as a baseline to find all
descendants.

app/models/ci/pipeline.rb

@@ -845,9 +845,15 @@ module Ci
     end
 
     def same_family_pipeline_ids
-      ::Gitlab::Ci::PipelineObjectHierarchy.new(
-        base_and_ancestors(same_project: true), options: { same_project: true }
-      ).base_and_descendants.select(:id)
+      if Feature.enabled?(:ci_root_ancestor_for_pipeline_family, project, default_enabled: false)
+        ::Gitlab::Ci::PipelineObjectHierarchy.new(
+          self.class.where(id: root_ancestor), options: { same_project: true }
+        ).base_and_descendants.select(:id)
+      else
+        ::Gitlab::Ci::PipelineObjectHierarchy.new(
+          base_and_ancestors(same_project: true), options: { same_project: true }
+        ).base_and_descendants.select(:id)
+      end
     end
 
     def build_with_artifacts_in_self_and_descendants(name)
@@ -869,6 +875,15 @@ module Ci
         .base_and_descendants
     end
 
+    def root_ancestor
+      return self unless child?
+
+      Gitlab::Ci::PipelineObjectHierarchy
+        .new(self.class.unscoped.where(id: id), options: { same_project: true })
+        .base_and_ancestors(hierarchy_order: :desc)
+        .first
+    end
+
     def bridge_triggered?
       source_bridge.present?
     end
@@ -878,7 +893,8 @@ module Ci
     end
 
     def child?
-      parent_pipeline.present?
+      parent_pipeline? && # child pipelines have `parent_pipeline` source
+        parent_pipeline.present?
     end
 
     def parent?

config/feature_flags/development/ci_root_ancestor_for_pipeline_family.yml

+---
+name: ci_root_ancestor_for_pipeline_family
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/46575 
+rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/287812 
+milestone: '13.7'
+type: development
+group: group::continuous integration
+default_enabled: false

spec/factories/ci/pipelines.rb

@@ -16,6 +16,7 @@ FactoryBot.define do
     transient { head_pipeline_of { nil } }
 
     transient { child_of { nil } }
+    transient { upstream_of { nil } }
 
     after(:build) do |pipeline, evaluator|
       if evaluator.child_of
@@ -30,9 +31,12 @@ FactoryBot.define do
 
       if evaluator.child_of
         bridge = create(:ci_bridge, pipeline: evaluator.child_of)
-        create(:ci_sources_pipeline,
-          source_job: bridge,
-          pipeline: pipeline)
+        create(:ci_sources_pipeline, source_job: bridge, pipeline: pipeline)
+      end
+
+      if evaluator.upstream_of
+        bridge = create(:ci_bridge, pipeline: pipeline)
+        create(:ci_sources_pipeline, source_job: bridge, pipeline: evaluator.upstream_of)
       end
     end
 

spec/models/ci/pipeline_spec.rb

@@ -269,7 +269,7 @@ RSpec.describe Ci::Pipeline, :mailer, factory_default: :keep do
     let!(:older_other_pipeline) { create(:ci_pipeline, project: project) }
 
     let!(:upstream_pipeline) { create(:ci_pipeline, project: project) }
-    let!(:child_pipeline) { create(:ci_pipeline, project: project) }
+    let!(:child_pipeline) { create(:ci_pipeline, child_of: upstream_pipeline) }
 
     let!(:other_pipeline) { create(:ci_pipeline, project: project) }
 
@@ -2754,13 +2754,9 @@ RSpec.describe Ci::Pipeline, :mailer, factory_default: :keep do
     end
 
     context 'when pipeline is child' do
-      let(:parent) { create(:ci_pipeline, project: pipeline.project) }
-      let(:sibling) { create(:ci_pipeline, project: pipeline.project) }
-
-      before do
-        create_source_pipeline(parent, pipeline)
-        create_source_pipeline(parent, sibling)
-      end
+      let(:parent) { create(:ci_pipeline, project: project) }
+      let!(:pipeline) { create(:ci_pipeline, child_of: parent) }
+      let!(:sibling) { create(:ci_pipeline, child_of: parent) }
 
       it 'returns parent sibling and self ids' do
         expect(subject).to contain_exactly(parent.id, pipeline.id, sibling.id)
@@ -2768,11 +2764,7 @@ RSpec.describe Ci::Pipeline, :mailer, factory_default: :keep do
     end
 
     context 'when pipeline is parent' do
-      let(:child) { create(:ci_pipeline, project: pipeline.project) }
-
-      before do
-        create_source_pipeline(pipeline, child)
-      end
+      let!(:child) { create(:ci_pipeline, child_of: pipeline) }
 
       it 'returns self and child ids' do
         expect(subject).to contain_exactly(pipeline.id, child.id)
@@ -2780,17 +2772,11 @@ RSpec.describe Ci::Pipeline, :mailer, factory_default: :keep do
     end
 
     context 'when pipeline is a child of a child pipeline' do
-      let(:ancestor) { create(:ci_pipeline, project: pipeline.project) }
-      let(:parent) { create(:ci_pipeline, project: pipeline.project) }
-      let(:cousin_parent) { create(:ci_pipeline, project: pipeline.project) }
-      let(:cousin) { create(:ci_pipeline, project: pipeline.project) }
-
-      before do
-        create_source_pipeline(ancestor, parent)
-        create_source_pipeline(ancestor, cousin_parent)
-        create_source_pipeline(parent, pipeline)
-        create_source_pipeline(cousin_parent, cousin)
-      end
+      let(:ancestor) { create(:ci_pipeline, project: project) }
+      let!(:parent) { create(:ci_pipeline, child_of: ancestor) }
+      let!(:pipeline) { create(:ci_pipeline, child_of: parent) }
+      let!(:cousin_parent) { create(:ci_pipeline, child_of: ancestor) }
+      let!(:cousin) { create(:ci_pipeline, child_of: cousin_parent) }
 
       it 'returns all family ids' do
         expect(subject).to contain_exactly(
@@ -2800,11 +2786,7 @@ RSpec.describe Ci::Pipeline, :mailer, factory_default: :keep do
     end
 
     context 'when pipeline is a triggered pipeline' do
-      let(:upstream) { create(:ci_pipeline, project: create(:project)) }
-
-      before do
-        create_source_pipeline(upstream, pipeline)
-      end
+      let!(:upstream) { create(:ci_pipeline, project: create(:project), upstream_of: pipeline)}
 
       it 'returns self id' do
         expect(subject).to contain_exactly(pipeline.id)
@@ -2812,6 +2794,46 @@ RSpec.describe Ci::Pipeline, :mailer, factory_default: :keep do
     end
   end
 
+  describe '#root_ancestor' do
+    subject { pipeline.root_ancestor }
+
+    let_it_be(:pipeline) { create(:ci_pipeline, project: project) }
+
+    context 'when pipeline is child of child pipeline' do
+      let!(:root_ancestor) { create(:ci_pipeline, project: project) }
+      let!(:parent_pipeline) { create(:ci_pipeline, child_of: root_ancestor) }
+      let!(:pipeline) { create(:ci_pipeline, child_of: parent_pipeline) }
+
+      it 'returns the root ancestor' do
+        expect(subject).to eq(root_ancestor)
+      end
+    end
+
+    context 'when pipeline is root ancestor' do
+      let!(:child_pipeline) { create(:ci_pipeline, child_of: pipeline) }
+
+      it 'returns itself' do
+        expect(subject).to eq(pipeline)
+      end
+    end
+
+    context 'when pipeline is standalone' do
+      it 'returns itself' do
+        expect(subject).to eq(pipeline)
+      end
+    end
+
+    context 'when pipeline is multi-project downstream pipeline' do
+      let!(:upstream_pipeline) do
+        create(:ci_pipeline, project: create(:project), upstream_of: pipeline)
+      end
+
+      it 'ignores cross project ancestors' do
+        expect(subject).to eq(pipeline)
+      end
+    end
+  end
+
   describe '#stuck?' do
     before do
       create(:ci_build, :pending, pipeline: pipeline)
@@ -3552,18 +3574,9 @@ RSpec.describe Ci::Pipeline, :mailer, factory_default: :keep do
   describe '#parent_pipeline' do
     let_it_be(:project) { create(:project) }
 
-    let(:pipeline) { create(:ci_pipeline, project: project) }
-
     context 'when pipeline is triggered by a pipeline from the same project' do
-      let(:upstream_pipeline) { create(:ci_pipeline, project: pipeline.project) }
-
-      before do
-        create(:ci_sources_pipeline,
-          source_pipeline: upstream_pipeline,
-          source_project: project,
-          pipeline: pipeline,
-          project: project)
-      end
+      let_it_be(:upstream_pipeline) { create(:ci_pipeline, project: project) }
+      let_it_be(:pipeline) { create(:ci_pipeline, child_of: upstream_pipeline) }
 
       it 'returns the parent pipeline' do
         expect(pipeline.parent_pipeline).to eq(upstream_pipeline)
@@ -3575,15 +3588,8 @@ RSpec.describe Ci::Pipeline, :mailer, factory_default: :keep do
     end
 
     context 'when pipeline is triggered by a pipeline from another project' do
-      let(:upstream_pipeline) { create(:ci_pipeline) }
-
-      before do
-        create(:ci_sources_pipeline,
-          source_pipeline: upstream_pipeline,
-          source_project: upstream_pipeline.project,
-          pipeline: pipeline,
-          project: project)
-      end
+      let(:pipeline) { create(:ci_pipeline, project: project) }
+      let!(:upstream_pipeline) { create(:ci_pipeline, project: create(:project), upstream_of: pipeline) }
 
       it 'returns nil' do
         expect(pipeline.parent_pipeline).to be_nil
@@ -3595,6 +3601,8 @@ RSpec.describe Ci::Pipeline, :mailer, factory_default: :keep do
     end
 
     context 'when pipeline is not triggered by a pipeline' do
+      let_it_be(:pipeline) { create(:ci_pipeline) }
+
       it 'returns nil' do
         expect(pipeline.parent_pipeline).to be_nil
       end