Fix GROUP BY in VSA label queries

This change makes sure VSA GROUP BY queries will not fail due to the
following error: "must appear in the GROUP BY clause or be used in
an aggregate function"

ee/lib/ee/gitlab/analytics/cycle_analytics/data_collector.rb

@@ -7,7 +7,7 @@ module EE
         module DataCollector
           def duration_chart_data
             strong_memoize(:duration_chart) do
-              ::Gitlab::Analytics::CycleAnalytics::DataForDurationChart.new(stage: stage, query: query).load
+              ::Gitlab::Analytics::CycleAnalytics::DataForDurationChart.new(stage: stage, params: params, query: query).load
             end
           end
         end

ee/lib/gitlab/analytics/cycle_analytics/data_for_duration_chart.rb

@@ -8,23 +8,23 @@ module Gitlab
 
         MAX_RESULTS = 500
 
-        def initialize(stage:, query:)
+        def initialize(stage:, params:, query:)
           @stage = stage
+          @params = params
           @query = query
         end
 
         # rubocop: disable CodeReuse/ActiveRecord
         def load
-          query
+          order_by_end_event(query)
             .select(round_duration_to_seconds.as('duration_in_seconds'), stage.end_event.timestamp_projection.as('finished_at'))
-            .reorder(stage.end_event.timestamp_projection.desc)
             .limit(MAX_RESULTS)
         end
         # rubocop: enable CodeReuse/ActiveRecord
 
         private
 
-        attr_reader :stage, :query
+        attr_reader :stage, :query, :params
       end
     end
   end

ee/lib/gitlab/analytics/cycle_analytics/stage_events/label_based_stage_event.rb

@@ -24,6 +24,10 @@ module Gitlab
             Arel.sql("#{join_expression_name}.created_at")
           end
 
+          def column_list
+            [timestamp_projection]
+          end
+
           # rubocop: disable CodeReuse/ActiveRecord
           def apply_query_customization(query)
             query

ee/lib/gitlab/analytics/cycle_analytics/summary/group/issue.rb

@@ -28,7 +28,8 @@ module Gitlab
             def issues_count
               issues = IssuesFinder.new(current_user, finder_params).execute
               issues = issues.where(projects: { id: options[:projects] }) if options[:projects].present?
-              issues.count
+
+              ::Issue.where(id: issues.select(:id)).count
             end
             # rubocop: enable CodeReuse/ActiveRecord
 

ee/spec/lib/gitlab/analytics/cycle_analytics/data_collector_spec.rb

@@ -210,7 +210,24 @@ RSpec.describe Gitlab::Analytics::CycleAnalytics::DataCollector do
           ).execute(issue)
         end
 
-        it_behaves_like 'custom cycle analytics stage'
+        it_behaves_like 'custom cycle analytics stage' do
+          context 'when filtering for two labels' do
+            let(:params) do
+              {
+                from: Time.new(2019),
+                to: Time.new(2020),
+                current_user: user,
+                label_name: [label.name, other_label.name]
+              }
+            end
+
+            subject { described_class.new(stage: stage, params: params) }
+
+            it 'does not raise query syntax error' do
+              expect { subject.records_fetcher.serialized_records }.not_to raise_error(ActiveRecord::StatementInvalid)
+            end
+          end
+        end
       end
 
       describe 'between issue creation time and issue label added time' do
@@ -491,6 +508,23 @@ RSpec.describe Gitlab::Analytics::CycleAnalytics::DataCollector do
         it_behaves_like 'filter examples'
       end
 
+      context 'when two labels are given' do
+        let(:label1) { create(:group_label, group: group) }
+        let(:label2) { create(:group_label, group: group) }
+
+        before do
+          MergeRequests::UpdateService.new(
+            merge_request.project,
+            user,
+            label_ids: [label1.id, label2.id]
+          ).execute(merge_request)
+
+          data_collector_params[:label_name] = [label1.name, label2.name]
+        end
+
+        it_behaves_like 'filter examples'
+      end
+
       context 'when `milestone_title` is given' do
         let(:milestone) { create(:milestone, group: group) }
 

ee/spec/lib/gitlab/analytics/cycle_analytics/summary/group/stage_summary_spec.rb

@@ -80,6 +80,27 @@ RSpec.describe Gitlab::Analytics::CycleAnalytics::Summary::Group::StageSummary d
         end
       end
 
+      context 'with `label_name` filter' do
+        let(:label1) { create(:group_label, group: group) }
+        let(:label2) { create(:group_label, group: group) }
+
+        before do
+          issue = project.issues.last
+
+          Issues::UpdateService.new(
+            issue.project,
+            user,
+            label_ids: [label1.id, label2.id]
+          ).execute(issue)
+        end
+
+        subject { described_class.new(group, options: { from: Time.now, current_user: user, label_name: [label1.name, label2.name] }).data }
+
+        it 'finds issue with two labels' do
+          expect(subject.first[:value]).to eq('1')
+        end
+      end
+
       context 'when `from` and `to` parameters are provided' do
         subject { described_class.new(group, options: { from: 10.days.ago, to: Time.now, current_user: user }).data }
 

lib/gitlab/analytics/cycle_analytics/records_fetcher.rb

@@ -90,9 +90,7 @@ module Gitlab
         end
 
         def ordered_and_limited_query
-          query
-            .reorder(stage.end_event.timestamp_projection.desc)
-            .limit(MAX_RECORDS)
+          order_by_end_event(query).limit(MAX_RECORDS)
         end
 
         def records

lib/gitlab/analytics/cycle_analytics/stage_events/issue_stage_end.rb

@@ -18,10 +18,14 @@ module Gitlab
           end
 
           def timestamp_projection
-            Arel::Nodes::NamedFunction.new('COALESCE', [
+            Arel::Nodes::NamedFunction.new('COALESCE', column_list)
+          end
+
+          def column_list
+            [
               issue_metrics_table[:first_associated_with_milestone_at],
               issue_metrics_table[:first_added_to_board_at]
-            ])
+            ]
           end
 
           # rubocop: disable CodeReuse/ActiveRecord

lib/gitlab/analytics/cycle_analytics/stage_events/metrics_based_stage_event.rb

@@ -10,6 +10,10 @@ module Gitlab
             query.joins(:metrics)
           end
           # rubocop: enable CodeReuse/ActiveRecord
+
+          def column_list
+            [timestamp_projection]
+          end
         end
       end
     end

lib/gitlab/analytics/cycle_analytics/stage_events/plan_stage_start.rb

@@ -18,10 +18,14 @@ module Gitlab
           end
 
           def timestamp_projection
-            Arel::Nodes::NamedFunction.new('COALESCE', [
+            Arel::Nodes::NamedFunction.new('COALESCE', column_list)
+          end
+
+          def column_list
+            [
               issue_metrics_table[:first_associated_with_milestone_at],
               issue_metrics_table[:first_added_to_board_at]
-            ])
+            ]
           end
 
           # rubocop: disable CodeReuse/ActiveRecord

lib/gitlab/analytics/cycle_analytics/stage_events/production_stage_end.rb

@@ -21,6 +21,10 @@ module Gitlab
             mr_metrics_table[:first_deployed_to_production_at]
           end
 
+          def column_list
+            [timestamp_projection]
+          end
+
           # rubocop: disable CodeReuse/ActiveRecord
           def apply_query_customization(query)
             query.joins(merge_requests_closing_issues: { merge_request: [:metrics] }).where(mr_metrics_table[:first_deployed_to_production_at].gteq(mr_table[:created_at]))

lib/gitlab/analytics/cycle_analytics/stage_events/stage_event.rb

@@ -32,6 +32,13 @@ module Gitlab
             raise NotImplementedError
           end
 
+          # List of columns that are referenced in the `timestamp_projection` expression
+          # Example timestamp projection: COALESCE(issue_metrics.created_at, issue_metrics.updated_at)
+          # Expected column list: issue_metrics.created_at, issue_metrics.updated_at
+          def column_list
+            []
+          end
+
           # Optionally a StageEvent may apply additional filtering or join other tables on the base query.
           def apply_query_customization(query)
             query

lib/gitlab/analytics/cycle_analytics/stage_query_helpers.rb

@@ -22,6 +22,29 @@ module Gitlab
             stage.start_event.timestamp_projection
           )
         end
+
+        # rubocop: disable CodeReuse/ActiveRecord
+        def order_by_end_event(query)
+          ordered_query = query.reorder(stage.end_event.timestamp_projection.desc)
+
+          # When filtering for more than one label, postgres requires the columns in ORDER BY to be present in the GROUP BY clause
+          if requires_grouping?
+            column_list = [
+              ordered_query.arel_table[:id],
+              *stage.end_event.column_list,
+              *stage.start_event.column_list
+            ]
+
+            ordered_query = ordered_query.group(column_list)
+          end
+
+          ordered_query
+        end
+        # rubocop: enable CodeReuse/ActiveRecord
+
+        def requires_grouping?
+          Array(params[:label_name]).size > 1
+        end
       end
     end
   end

spec/support/shared_examples/lib/gitlab/cycle_analytics/event_shared_examples.rb

@@ -8,6 +8,7 @@ RSpec.shared_examples_for 'cycle analytics event' do
   it { expect(described_class.identifier).to be_a_kind_of(Symbol) }
   it { expect(instance.object_type.ancestors).to include(ApplicationRecord) }
   it { expect(instance).to respond_to(:timestamp_projection) }
+  it { expect(instance.column_list).to be_a_kind_of(Array) }
 
   describe '#apply_query_customization' do
     it 'expects an ActiveRecord::Relation object as argument and returns a modified version of it' do