Merge branch 'ahegyi_issue_rebalancing_optimization' into 'master'

Optimize issue rebalancing UPDATE query [RUN ALL RSPEC] [RUN AS-IF-FOSS]

See merge request gitlab-org/gitlab!53384

app/services/issue_rebalancing_service.rb

@@ -17,8 +17,21 @@ class IssueRebalancingService
 
     start = RelativePositioning::START_POSITION - (gaps / 2) * gap_size
 
+    if Feature.enabled?(:issue_rebalancing_optimization)
       Issue.transaction do
-      indexed_ids.each_slice(100) { |pairs| assign_positions(start, pairs) }
+        assign_positions(start, indexed_ids)
+          .sort_by(&:first)
+          .each_slice(100) do |pairs_with_position|
+          update_positions(pairs_with_position, 'rebalance issue positions in batches ordered by id')
+        end
+      end
+    else
+      Issue.transaction do
+        indexed_ids.each_slice(100) do |pairs|
+          pairs_with_position = assign_positions(start, pairs)
+          update_positions(pairs_with_position, 'rebalance issue positions')
+        end
+      end
     end
   end
 
@@ -32,13 +45,22 @@ class IssueRebalancingService
   end
   # rubocop: enable CodeReuse/ActiveRecord
 
-  # rubocop: disable CodeReuse/ActiveRecord
-  def assign_positions(start, positions)
-    values = positions.map do |id, index|
-      "(#{id}, #{start + (index * gap_size)})"
+  def assign_positions(start, pairs)
+    pairs.map do |id, index|
+      [id, start + (index * gap_size)]
+    end
+  end
+
+  def update_positions(pairs_with_position, query_name)
+    values = pairs_with_position.map do |id, index|
+      "(#{id}, #{index})"
     end.join(', ')
 
-    Issue.connection.exec_query(<<~SQL, "rebalance issue positions")
+    run_update_query(values, query_name)
+  end
+
+  def run_update_query(values, query_name)
+    Issue.connection.exec_query(<<~SQL, query_name)
       WITH cte(cte_id, new_pos) AS (
        SELECT *
        FROM (VALUES #{values}) as t (id, pos)
@@ -49,7 +71,6 @@ class IssueRebalancingService
       WHERE cte_id = id
     SQL
   end
-  # rubocop: enable CodeReuse/ActiveRecord
 
   def issue_count
     @issue_count ||= base.count

config/feature_flags/development/issue_rebalancing_optimization.yml

+---
+name: issue_rebalancing_optimization
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/53384
+rollout_issue_url:
+milestone: '13.9'
+type: development
+group: group::project management
+default_enabled: false

spec/services/issue_rebalancing_service_spec.rb

@@ -32,6 +32,7 @@ RSpec.describe IssueRebalancingService do
     project.reload.issues.reorder(relative_position: :asc).to_a
   end
 
+  shared_examples 'IssueRebalancingService shared examples' do
     it 'rebalances a set of issues with clumps at the end and start' do
       all_issues = start_clump + unclumped + end_clump.reverse
       service = described_class.new(project.issues.first)
@@ -98,4 +99,21 @@ RSpec.describe IssueRebalancingService do
 
       expect { described_class.new(issue).execute }.to raise_error(described_class::TooManyIssues)
     end
+  end
+
+  context 'when issue_rebalancing_optimization feature flag is on' do
+    before do
+      stub_feature_flags(issue_rebalancing_optimization: true)
+    end
+
+    it_behaves_like 'IssueRebalancingService shared examples'
+  end
+
+  context 'when issue_rebalancing_optimization feature flag is on' do
+    before do
+      stub_feature_flags(issue_rebalancing_optimization: false)
+    end
+
+    it_behaves_like 'IssueRebalancingService shared examples'
+  end
 end