Test performance improvements

This includes a bunch of optimizations (avoiding re-creating issues,
being very careful about resets) that means we can run over a range of
size 6 (2606 examples) in about 4min 30s.

spec/lib/gitlab/relative_positioning/mover_spec.rb

@@ -3,57 +3,116 @@
 require 'spec_helper'
 
 RSpec.describe RelativePositioning::Mover do
-  let_it_be(:default_user) { create_default(:user) }
-  let_it_be(:project, reload: true) { create(:project) }
-
-  def create_issue(pos)
-    create(:issue, project: project, relative_position: pos)
+  let_it_be(:user) { create(:user) }
+  let_it_be(:one_sibling, reload: true) { create(:project, creator: user, namespace: user.namespace) }
+  let_it_be(:one_free_space, reload: true) { create(:project, creator: user, namespace: user.namespace) }
+  let_it_be(:fully_occupied, reload: true) { create(:project, creator: user, namespace: user.namespace) }
+  let_it_be(:no_issues, reload: true) { create(:project, creator: user, namespace: user.namespace) }
+  let_it_be(:three_sibs, reload: true) { create(:project, creator: user, namespace: user.namespace) }
+
+  def create_issue(pos, parent = project)
+    create(:issue, author: user, project: parent, relative_position: pos)
   end
 
-  # Increase the range size to convice yourself that this covers ALL arrangements
-  range = (101..104)
+  range = (101..106)
   indices = (0..).take(range.size)
 
   let(:start) { ((range.first + range.last) / 2.0).floor }
 
   subject { described_class.new(start, range) }
 
+  let_it_be(:full_set) do
+    range.each_with_index.map do |pos, i|
+      create(:issue, iid: i.succ, project: fully_occupied, relative_position: pos)
+    end
+  end
+
+  let_it_be(:sole_sibling) { create(:issue, iid: 1, project: one_sibling, relative_position: nil) }
+  let_it_be(:one_sibling_set) { [sole_sibling] }
+  let_it_be(:one_free_space_set) do
+    indices.drop(1).map { |iid| create(:issue, project: one_free_space, iid: iid.succ) }
+  end
+  let_it_be(:three_sibs_set) do
+    [1, 2, 3].map { |iid| create(:issue, iid: iid, project: three_sibs) }
+  end
+
+  def set_positions(positions)
+    vals = issues.zip(positions).map do |issue, pos|
+      issue.relative_position = pos
+      "(#{issue.id}, #{pos})"
+    end.join(', ')
+
+    Issue.connection.exec_query(<<~SQL, 'set-positions')
+      WITH cte(cte_id, new_pos) AS (
+       SELECT * FROM (VALUES #{vals}) as t (id, pos)
+      )
+      UPDATE issues SET relative_position = new_pos FROM cte WHERE id = cte_id
+      ;
+    SQL
+  end
+
+  def ids_in_position_order
+    project.issues.reorder(:relative_position).pluck(:id)
+  end
+
+  def relative_positions
+    project.issues.pluck(:relative_position)
+  end
+
   describe '#move_to_end' do
+    def max_position
+      project.issues.maximum(:relative_position)
+    end
+
+    def move_to_end(issue)
+      subject.move_to_end(issue)
+      issue.save!
+    end
+
     shared_examples 'able to place a new item at the end' do
       it 'can place any new item' do
-        existing_issues = project.issues.to_a
+        existing_issues = ids_in_position_order
         new_item = create_issue(nil)
 
-        subject.move_to_end(new_item)
-        new_item.save!
+        expect do
+          move_to_end(new_item)
+        end.to change { project.issues.pluck(:id, :relative_position) }
 
-        expect(new_item.relative_position).to eq(project.issues.maximum(:relative_position))
-        expect(project.issues.reorder(:relative_position).pluck(:id)).to eq(existing_issues.map(&:id) + [new_item.id])
+        expect(new_item.relative_position).to eq(max_position)
+        expect(relative_positions).to all(be_between(range.first, range.last))
+        expect(ids_in_position_order).to eq(existing_issues + [new_item.id])
       end
     end
 
     shared_examples 'able to move existing items to the end' do
       it 'can move any existing item' do
+        issues = project.issues.reorder(:relative_position).to_a
         issue = issues[index]
         other_issues = issues.reject { |i| i == issue }
+        expect(relative_positions).to all(be_between(range.first, range.last))
+
+        if issues.last == issue
+          move_to_end(issue) # May not change the positions
+        else
+          expect do
+            move_to_end(issue)
+          end.to change { project.issues.pluck(:id, :relative_position) }
+        end
 
-        subject.move_to_end(issue)
-        issue.save!
         project.reset
 
-        expect(project.issues.pluck(:relative_position)).to all(be_between(range.first, range.last))
-        expect(issue.relative_position).to eq(project.issues.maximum(:relative_position))
-        expect(project.issues.reorder(:relative_position).pluck(:id)).to eq(other_issues.map(&:id) + [issue.id])
+        expect(relative_positions).to all(be_between(range.first, range.last))
+        expect(issue.relative_position).to eq(max_position)
+        expect(ids_in_position_order).to eq(other_issues.map(&:id) + [issue.id])
       end
     end
 
     context 'all positions are taken' do
-      let_it_be(:issues) do
-        range.map { |pos| create_issue(pos) }
-      end
+      let(:issues) { full_set }
+      let(:project) { fully_occupied }
 
       it 'raises an error when placing a new item' do
-        new_item = create(:issue, project: project, relative_position: nil)
+        new_item = create_issue(nil)
 
         expect { subject.move_to_end(new_item) }.to raise_error(RelativePositioning::NoSpaceLeft)
       end
@@ -66,6 +125,9 @@ RSpec.describe RelativePositioning::Mover do
     end
 
     context 'there are no siblings' do
+      let(:issues) { [] }
+      let(:project) { no_issues }
+
       it_behaves_like 'able to place a new item at the end'
     end
 
@@ -73,9 +135,14 @@ RSpec.describe RelativePositioning::Mover do
       where(:pos) { range.to_a }
 
       with_them do
-        let!(:issues) { [create_issue(pos)] }
+        let(:issues) { one_sibling_set }
+        let(:project) { one_sibling }
         let(:index) { 0 }
 
+        before do
+          sole_sibling.reset.update!(relative_position: pos)
+        end
+
         it_behaves_like 'able to place a new item at the end'
 
         it_behaves_like 'able to move existing items to the end'
@@ -84,12 +151,18 @@ RSpec.describe RelativePositioning::Mover do
 
     context 'at least one position is free' do
       where(:free_space, :index) do
-        range.to_a.product((0..).take(range.size - 1).to_a)
+        is = indices.take(range.size - 1)
+
+        range.to_a.product(is)
       end
 
       with_them do
-        let!(:issues) do
-          range.reject { |x| x == free_space }.map { |pos| create_issue(pos) }
+        let(:issues) { one_free_space_set }
+        let(:project) { one_free_space }
+
+        before do
+          positions = range.reject { |x| x == free_space }
+          set_positions(positions)
         end
 
         it_behaves_like 'able to place a new item at the end'
@@ -100,38 +173,56 @@ RSpec.describe RelativePositioning::Mover do
   end
 
   describe '#move_to_start' do
+    def min_position
+      project.issues.minimum(:relative_position)
+    end
+
+    def move_to_start(issue)
+      subject.move_to_start(issue)
+      issue.save!
+    end
+
     shared_examples 'able to place a new item at the start' do
       it 'can place any new item' do
-        existing_issues = project.issues.to_a
+        existing_issues = ids_in_position_order
         new_item = create_issue(nil)
 
-        subject.move_to_start(new_item)
-        new_item.save!
+        expect do
+          move_to_start(new_item)
+        end.to change { project.issues.pluck(:id, :relative_position) }
 
-        expect(new_item.relative_position).to eq(project.issues.minimum(:relative_position))
-        expect(project.issues.reorder(:relative_position).pluck(:id)).to eq([new_item.id] + existing_issues.map(&:id))
+        expect(relative_positions).to all(be_between(range.first, range.last))
+        expect(new_item.relative_position).to eq(min_position)
+        expect(ids_in_position_order).to eq([new_item.id] + existing_issues)
       end
     end
 
     shared_examples 'able to move existing items to the start' do
       it 'can move any existing item' do
+        issues = project.issues.reorder(:relative_position).to_a
         issue = issues[index]
         other_issues = issues.reject { |i| i == issue }
+        expect(relative_positions).to all(be_between(range.first, range.last))
+
+        if issues.first == issue
+          move_to_start(issue) # May not change the positions
+        else
+          expect do
+            move_to_start(issue)
+          end.to change { project.issues.pluck(:id, :relative_position) }
+        end
 
-        subject.move_to_start(issue)
-        issue.save!
         project.reset
 
-        expect(project.issues.pluck(:relative_position)).to all(be_between(range.first, range.last))
-        expect(issue.relative_position).to eq(project.issues.minimum(:relative_position))
-        expect(project.issues.reorder(:relative_position).pluck(:id)).to eq([issue.id] + other_issues.map(&:id))
+        expect(relative_positions).to all(be_between(range.first, range.last))
+        expect(issue.relative_position).to eq(min_position)
+        expect(ids_in_position_order).to eq([issue.id] + other_issues.map(&:id))
       end
     end
 
     context 'all positions are taken' do
-      let_it_be(:issues) do
-        range.map { |pos| create_issue(pos) }
-      end
+      let(:issues) { full_set }
+      let(:project) { fully_occupied }
 
       it 'raises an error when placing a new item' do
         new_item = create(:issue, project: project, relative_position: nil)
@@ -147,6 +238,9 @@ RSpec.describe RelativePositioning::Mover do
     end
 
     context 'there are no siblings' do
+      let(:project) { no_issues }
+      let(:issues) { [] }
+
       it_behaves_like 'able to place a new item at the start'
     end
 
@@ -154,9 +248,14 @@ RSpec.describe RelativePositioning::Mover do
       where(:pos) { range.to_a }
 
       with_them do
-        let!(:issues) { [create_issue(pos)] }
+        let(:issues) { one_sibling_set }
+        let(:project) { one_sibling }
         let(:index) { 0 }
 
+        before do
+          sole_sibling.reset.update!(relative_position: pos)
+        end
+
         it_behaves_like 'able to place a new item at the start'
 
         it_behaves_like 'able to move existing items to the start'
@@ -169,8 +268,11 @@ RSpec.describe RelativePositioning::Mover do
       end
 
       with_them do
-        let!(:issues) do
-          range.reject { |x| x == free_space }.map { |pos| create_issue(pos) }
+        let(:issues) { one_free_space_set }
+        let(:project) { one_free_space }
+
+        before do
+          set_positions(range.reject { |x| x == free_space })
         end
 
         it_behaves_like 'able to place a new item at the start'
@@ -230,10 +332,14 @@ RSpec.describe RelativePositioning::Mover do
     end
 
     shared_examples 'able to move an existing item' do
-      let(:item) { issues[index] }
+      let(:all_issues) { project.issues.reorder(:relative_position).to_a }
+      let(:item) { all_issues[index] }
       let(:positions) { project.reset.issues.pluck(:relative_position) }
-      let(:other_issues) { project.issues.reorder(:relative_position).to_a.reject { |i| i == item } }
+      let(:other_issues) { all_issues.reject { |i| i == item } }
       let!(:previous_order) { other_issues.map(&:id) }
+      let(:new_order) do
+        project.issues.where.not(id: item.id).reorder(:relative_position).pluck(:id)
+      end
 
       it 'can place any item betwen two others' do
         subject.move(item, lhs, rhs)
@@ -245,8 +351,13 @@ RSpec.describe RelativePositioning::Mover do
         expect(positions).to match_array(positions.uniq)
         expect(item.relative_position).to be_between(lhs.relative_position, rhs.relative_position)
 
-        ids = project.issues.reorder(:relative_position).pluck(:id).reject { |id| id == item.id }
-        expect(ids).to eq(previous_order)
+        expect(new_order).to eq(previous_order)
+      end
+
+      def sequence(expected_sequence)
+        range = (expected_sequence.first.relative_position..expected_sequence.last.relative_position)
+
+        project.issues.reorder(:relative_position).where(relative_position: range)
       end
 
       it 'can place any item after another' do
@@ -259,14 +370,10 @@ RSpec.describe RelativePositioning::Mover do
         expect(item.relative_position).to be >= lhs.relative_position
 
         expected_sequence = [lhs, item].uniq
-        sequence = project.issues
-          .reorder(:relative_position)
-          .where(relative_position: (expected_sequence.first.relative_position..expected_sequence.last.relative_position))
 
-        expect(sequence).to eq(expected_sequence)
+        expect(sequence(expected_sequence)).to eq(expected_sequence)
 
-        ids = project.issues.reorder(:relative_position).pluck(:id).reject { |id| id == item.id }
-        expect(ids).to eq(previous_order)
+        expect(new_order).to eq(previous_order)
       end
 
       it 'can place any item before another' do
@@ -279,31 +386,24 @@ RSpec.describe RelativePositioning::Mover do
         expect(item.relative_position).to be <= rhs.relative_position
 
         expected_sequence = [item, rhs].uniq
-        sequence = project.issues
-          .reorder(:relative_position)
-          .where(relative_position: (expected_sequence.first.relative_position..expected_sequence.last.relative_position))
 
-        expect(sequence).to eq(expected_sequence)
+        expect(sequence(expected_sequence)).to eq(expected_sequence)
 
-        ids = project.issues.reorder(:relative_position).pluck(:id).reject { |id| id == item.id }
-        expect(ids).to eq(previous_order)
+        expect(new_order).to eq(previous_order)
       end
     end
 
     context 'all positions are taken' do
-      let_it_be(:issues) { range.map { |pos| create_issue(pos) } }
+      let(:issues) { full_set }
+      let(:project) { fully_occupied }
 
       where(:idx_a, :idx_b) do
         indices.product(indices).select { |a, b| a < b }
       end
 
       with_them do
-        let(:lhs) { issues[idx_a] }
-        let(:rhs) { issues[idx_b] }
-
-        before do
-          issues.each(&:reset)
-        end
+        let(:lhs) { issues[idx_a].reset }
+        let(:rhs) { issues[idx_b].reset }
 
         it 'raises an error when placing a new item anywhere' do
           new_item = create_issue(nil)
@@ -327,6 +427,8 @@ RSpec.describe RelativePositioning::Mover do
     end
 
     context 'there are no siblings' do
+      let(:project) { no_issues }
+
       it 'raises an ArgumentError when both first and last are nil' do
         new_item = create_issue(nil)
 
@@ -338,15 +440,21 @@ RSpec.describe RelativePositioning::Mover do
       where(:pos_movable, :pos_a, :pos_b) do
         xs = range.to_a
 
-        xs.product(xs).product(xs).map(&:flatten).select { |vals| vals == vals.uniq }
+        xs.product(xs).product(xs).map(&:flatten)
+          .select { |vals| vals == vals.uniq && vals[1] < vals[2] }
       end
 
       with_them do
-        let!(:issues) { ([pos_movable] + [pos_a, pos_b].sort).map { |p| create_issue(p) } }
+        let(:issues) { three_sibs_set }
+        let(:project) { three_sibs }
         let(:index) { 0 }
         let(:lhs) { issues[1] }
         let(:rhs) { issues[2] }
 
+        before do
+          set_positions([pos_movable, pos_a, pos_b])
+        end
+
         it_behaves_like 'able to move a new item'
         it_behaves_like 'able to move an existing item'
       end
@@ -362,15 +470,16 @@ RSpec.describe RelativePositioning::Mover do
       end
 
       with_them do
-        let!(:issues) do
-          range.reject { |x| x == free_space }.map { |pos| create_issue(pos) }
-        end
-
+        let(:issues) { one_free_space_set }
+        let(:project) { one_free_space }
         let(:lhs) { issues[pos_a] }
         let(:rhs) { issues[pos_b] }
 
-        it_behaves_like 'able to move a new item'
+        before do
+          set_positions(range.reject { |x| x == free_space })
+        end
 
+        it_behaves_like 'able to move a new item'
         it_behaves_like 'able to move an existing item'
       end
     end