Revert "Merge branch 'ajk-relative-positioning-improvements' into 'master'"

This reverts merge request !37724

.rubocop_todo.yml

@@ -1323,6 +1323,7 @@ Rails/SaveBang:
     - 'spec/support/shared_examples/models/members_notifications_shared_example.rb'
     - 'spec/support/shared_examples/models/mentionable_shared_examples.rb'
     - 'spec/support/shared_examples/models/project_latest_successful_build_for_shared_examples.rb'
+    - 'spec/support/shared_examples/models/relative_positioning_shared_examples.rb'
     - 'spec/support/shared_examples/models/slack_mattermost_notifications_shared_examples.rb'
     - 'spec/support/shared_examples/models/update_project_statistics_shared_examples.rb'
     - 'spec/support/shared_examples/models/with_uploads_shared_examples.rb'

app/models/concerns/relative_positioning.rb

@@ -3,15 +3,11 @@
 # This module makes it possible to handle items as a list, where the order of items can be easily altered
 # Requirements:
 #
-# The model must have the following named columns:
-#  - id: integer
-#  - relative_position: integer
+# - Only works for ActiveRecord models
+# - relative_position integer field must present on the model
+# - This module uses GROUP BY: the model should have a parent relation, example: project -> issues, project is the parent relation (issues table has a parent_id column)
 #
-# The model must support a concept of siblings via a child->parent relationship,
-# to enable rebalancing and `GROUP BY` in queries.
-# - example: project -> issues, project is the parent relation (issues table has a parent_id column)
-#
-# Two class methods must be defined when including this concern:
+# Setup like this in the body of your class:
 #
 #     include RelativePositioning
 #
@@ -28,162 +24,66 @@
 module RelativePositioning
   extend ActiveSupport::Concern
 
-  STEPS = 10
-  IDEAL_DISTANCE = 2**(STEPS - 1) + 1
-
-  MIN_POSITION = Gitlab::Database::MIN_INT_VALUE
-  START_POSITION = 0
+  MIN_POSITION = 0
+  START_POSITION = Gitlab::Database::MAX_INT_VALUE / 2
   MAX_POSITION = Gitlab::Database::MAX_INT_VALUE
-
-  MAX_GAP = IDEAL_DISTANCE * 2
-  MIN_GAP = 2
-
-  NoSpaceLeft = Class.new(StandardError)
+  IDEAL_DISTANCE = 500
 
   class_methods do
     def move_nulls_to_end(objects)
-      move_nulls(objects, at_end: true)
+      objects = objects.reject(&:relative_position)
+      return if objects.empty?
+
+      self.transaction do
+        max_relative_position = objects.first.max_relative_position
+
+        objects.each do |object|
+          relative_position = position_between(max_relative_position || START_POSITION, MAX_POSITION)
+          object.update_column(:relative_position, relative_position)
+
+          max_relative_position = relative_position
+        end
+      end
     end
 
     def move_nulls_to_start(objects)
-      move_nulls(objects, at_end: false)
+      objects = objects.reject(&:relative_position)
+      return if objects.empty?
+
+      self.transaction do
+        min_relative_position = objects.first.min_relative_position
+
+        objects.reverse_each do |object|
+          relative_position = position_between(MIN_POSITION, min_relative_position || START_POSITION)
+          object.update_column(:relative_position, relative_position)
+
+          min_relative_position = relative_position
+        end
+      end
     end
 
     # This method takes two integer values (positions) and
     # calculates the position between them. The range is huge as
-    # the maximum integer value is 2147483647.
-    #
-    # We avoid open ranges by clamping the range to [MIN_POSITION, MAX_POSITION].
-    #
-    # Then we handle one of three cases:
-    #  - If the gap is too small, we raise NoSpaceLeft
-    #  - If the gap is larger than MAX_GAP, we place the new position at most
-    #    IDEAL_DISTANCE from the edge of the gap.
-    #  - otherwise we place the new position at the midpoint.
-    #
-    # The new position will always satisfy: pos_before <= midpoint <= pos_after
-    #
-    # As a precondition, the gap between pos_before and pos_after MUST be >= 2.
-    # If the gap is too small, NoSpaceLeft is raised.
-    #
-    # This class method should only be called by instance methods of this module, which
-    # include handling for minimum gap size.
-    #
-    # @raises NoSpaceLeft
-    # @api private
+    # the maximum integer value is 2147483647. We are incrementing position by IDEAL_DISTANCE * 2 every time
+    # when we have enough space. If distance is less than IDEAL_DISTANCE, we are calculating an average number.
     def position_between(pos_before, pos_after)
       pos_before ||= MIN_POSITION
       pos_after ||= MAX_POSITION
 
       pos_before, pos_after = [pos_before, pos_after].sort
 
-      gap_width = pos_after - pos_before
-      midpoint = [pos_after - 1, pos_before + (gap_width / 2)].min
+      halfway = (pos_after + pos_before) / 2
+      distance_to_halfway = pos_after - halfway
 
-      if gap_width < MIN_GAP
-        raise NoSpaceLeft
-      elsif gap_width > MAX_GAP
+      if distance_to_halfway < IDEAL_DISTANCE
+        halfway
+      else
         if pos_before == MIN_POSITION
           pos_after - IDEAL_DISTANCE
         elsif pos_after == MAX_POSITION
           pos_before + IDEAL_DISTANCE
         else
-          midpoint
-        end
-      else
-        midpoint
-      end
-    end
-
-    private
-
-    # @api private
-    def gap_size(object, gaps:, at_end:, starting_from:)
-      total_width = IDEAL_DISTANCE * gaps
-      size = if at_end && starting_from + total_width >= MAX_POSITION
-               (MAX_POSITION - starting_from) / gaps
-             elsif !at_end && starting_from - total_width <= MIN_POSITION
-               (starting_from - MIN_POSITION) / gaps
-             else
-               IDEAL_DISTANCE
-             end
-
-      # Shift max elements leftwards if there isn't enough space
-      return [size, starting_from] if size >= MIN_GAP
-
-      order = at_end ? :desc : :asc
-      terminus = object
-        .send(:relative_siblings) # rubocop:disable GitlabSecurity/PublicSend
-        .where('relative_position IS NOT NULL')
-        .order(relative_position: order)
-        .first
-
-      if at_end
-        terminus.move_sequence_before(true)
-        max_relative_position = terminus.reset.relative_position
-        [[(MAX_POSITION - max_relative_position) / gaps, IDEAL_DISTANCE].min, max_relative_position]
-      else
-        terminus.move_sequence_after(true)
-        min_relative_position = terminus.reset.relative_position
-        [[(min_relative_position - MIN_POSITION) / gaps, IDEAL_DISTANCE].min, min_relative_position]
-      end
-    end
-
-    # @api private
-    # @param [Array<RelativePositioning>] objects The objects to give positions to. The relative
-    #                                             order will be preserved (i.e. when this method returns,
-    #                                             objects.first.relative_position < objects.last.relative_position)
-    # @param [Boolean] at_end: The placement.
-    #                          If `true`, then all objects with `null` positions are placed _after_
-    #                          all siblings with positions. If `false`, all objects with `null`
-    #                          positions are placed _before_ all siblings with positions.
-    def move_nulls(objects, at_end:)
-      objects = objects.reject(&:relative_position)
-      return if objects.empty?
-
-      representative = objects.first
-      number_of_gaps = objects.size + 1 # 1 at left, one between each, and one at right
-      position = if at_end
-                   representative.max_relative_position
-                 else
-                   representative.min_relative_position
-                 end
-
-      position ||= START_POSITION # If there are no positioned siblings, start from START_POSITION
-
-      gap, position = gap_size(representative, gaps: number_of_gaps, at_end: at_end, starting_from: position)
-
-      # Raise if we could not make enough space
-      raise NoSpaceLeft if gap < MIN_GAP
-
-      indexed = objects.each_with_index.to_a
-      starting_from = at_end ? position : position - (gap * number_of_gaps)
-
-      # Some classes are polymorphic, and not all siblings are in the same table.
-      by_model = indexed.group_by { |pair| pair.first.class }
-
-      by_model.each do |model, pairs|
-        model.transaction do
-          pairs.each_slice(100) do |batch|
-            # These are known to be integers, one from the DB, and the other
-            # calculated by us, and thus safe to interpolate
-            values = batch.map do |obj, i|
-              pos = starting_from + gap * (i + 1)
-              obj.relative_position = pos
-              "(#{obj.id}, #{pos})"
-            end.join(', ')
-
-            model.connection.exec_query(<<~SQL, "UPDATE #{model.table_name} positions")
-              WITH cte(cte_id, new_pos) AS (
-               SELECT *
-               FROM (VALUES #{values}) as t (id, pos)
-              )
-              UPDATE #{model.table_name}
-              SET relative_position = cte.new_pos
-              FROM cte
-              WHERE cte_id = id
-            SQL
-          end
+          halfway
         end
       end
     end
@@ -197,12 +97,11 @@ module RelativePositioning
     calculate_relative_position('MAX', &block)
   end
 
-  def prev_relative_position(ignoring: nil)
+  def prev_relative_position
     prev_pos = nil
 
     if self.relative_position
       prev_pos = max_relative_position do |relation|
-        relation = relation.id_not_in(ignoring.id) if ignoring.present?
         relation.where('relative_position < ?', self.relative_position)
       end
     end
@@ -210,12 +109,11 @@ module RelativePositioning
     prev_pos
   end
 
-  def next_relative_position(ignoring: nil)
+  def next_relative_position
     next_pos = nil
 
     if self.relative_position
       next_pos = min_relative_position do |relation|
-        relation = relation.id_not_in(ignoring.id) if ignoring.present?
         relation.where('relative_position > ?', self.relative_position)
       end
     end
@@ -227,44 +125,24 @@ module RelativePositioning
     return move_after(before) unless after
     return move_before(after) unless before
 
+    # If there is no place to insert an item we need to create one by moving the item
+    # before this and all preceding items until there is a gap
     before, after = after, before if after.relative_position < before.relative_position
-
-    pos_left = before.relative_position
-    pos_right = after.relative_position
-
-    if pos_right - pos_left < MIN_GAP
-      # Not enough room! Make space by shifting all previous elements to the left
-      # if there is enough space, else to the right
-      gap = after.send(:find_next_gap_before) # rubocop:disable GitlabSecurity/PublicSend
-
-      if gap.present?
-        after.move_sequence_before(next_gap: gap)
-        pos_left -= optimum_delta_for_gap(gap)
-      else
-        before.move_sequence_after
-        pos_right = after.reset.relative_position
-      end
+    if (after.relative_position - before.relative_position) < 2
+      after.move_sequence_before
+      before.reset
     end
 
-    new_position = self.class.position_between(pos_left, pos_right)
-
-    self.relative_position = new_position
+    self.relative_position = self.class.position_between(before.relative_position, after.relative_position)
   end
 
   def move_after(before = self)
     pos_before = before.relative_position
-    pos_after = before.next_relative_position(ignoring: self)
-
-    if pos_before == MAX_POSITION || gap_too_small?(pos_after, pos_before)
-      gap = before.send(:find_next_gap_after) # rubocop:disable GitlabSecurity/PublicSend
+    pos_after = before.next_relative_position
 
-      if gap.nil?
-        before.move_sequence_before(true)
-        pos_before = before.reset.relative_position
-      else
-        before.move_sequence_after(next_gap: gap)
-        pos_after += optimum_delta_for_gap(gap)
-      end
+    if pos_after && (pos_after - pos_before) < 2
+      before.move_sequence_after
+      pos_after = before.next_relative_position
     end
 
     self.relative_position = self.class.position_between(pos_before, pos_after)
@@ -272,168 +150,80 @@ module RelativePositioning
 
   def move_before(after = self)
     pos_after = after.relative_position
-    pos_before = after.prev_relative_position(ignoring: self)
+    pos_before = after.prev_relative_position
 
-    if pos_after == MIN_POSITION || gap_too_small?(pos_before, pos_after)
-      gap = after.send(:find_next_gap_before) # rubocop:disable GitlabSecurity/PublicSend
-
-      if gap.nil?
-        after.move_sequence_after(true)
-        pos_after = after.reset.relative_position
-      else
-        after.move_sequence_before(next_gap: gap)
-        pos_before -= optimum_delta_for_gap(gap)
-      end
+    if pos_before && (pos_after - pos_before) < 2
+      after.move_sequence_before
+      pos_before = after.prev_relative_position
     end
 
     self.relative_position = self.class.position_between(pos_before, pos_after)
   end
 
   def move_to_end
-    max_pos = max_relative_position
-
-    self.relative_position = max_pos.nil? ? START_POSITION : self.class.position_between(max_pos, MAX_POSITION)
+    self.relative_position = self.class.position_between(max_relative_position || START_POSITION, MAX_POSITION)
   end
 
   def move_to_start
-    min_pos = max_relative_position
-
-    self.relative_position = min_pos.nil? ? START_POSITION : self.class.position_between(MIN_POSITION, min_pos)
+    self.relative_position = self.class.position_between(min_relative_position || START_POSITION, MIN_POSITION)
   end
 
   # Moves the sequence before the current item to the middle of the next gap
-  # For example, we have
-  #
-  #   5 . . . . . 11 12 13 14 [15] 16 . 17
-  #               -----------
-  #
-  # This moves the sequence [11 12 13 14] to [8 9 10 11], so we have:
-  #
-  #   5 . . 8 9 10 11 . . . [15] 16 . 17
-  #         ---------
-  #
-  # Creating a gap to the left of the current item. We can understand this as
-  # dividing the 5 spaces between 5 and 11 into two smaller gaps of 2 and 3.
-  #
-  # If `include_self` is true, the current item will also be moved, creating a
-  # gap to the right of the current item:
-  #
-  #   5 . . 8 9 10 11 [14] . . . 16 . 17
-  #         --------------
-  #
-  # As an optimization, the gap can be precalculated and passed to this method.
-  #
-  # @api private
-  # @raises NoSpaceLeft if the sequence cannot be moved
-  def move_sequence_before(include_self = false, next_gap: find_next_gap_before)
-    raise NoSpaceLeft unless next_gap.present?
-
+  # For example, we have 5 11 12 13 14 15 and the current item is 15
+  # This moves the sequence 11 12 13 14 to 8 9 10 11
+  def move_sequence_before
+    next_gap = find_next_gap_before
     delta = optimum_delta_for_gap(next_gap)
 
-    move_sequence(next_gap[:start], relative_position, -delta, include_self)
+    move_sequence(next_gap[:start], relative_position, -delta)
   end
 
   # Moves the sequence after the current item to the middle of the next gap
-  # For example, we have:
-  #
-  #   8 . 10 [11] 12 13 14 15 . . . . . 21
-  #               -----------
-  #
-  # This moves the sequence [12 13 14 15] to [15 16 17 18], so we have:
-  #
-  #   8 . 10 [11] . . . 15 16 17 18 . . 21
-  #                     -----------
-  #
-  # Creating a gap to the right of the current item. We can understand this as
-  # dividing the 5 spaces between 15 and 21 into two smaller gaps of 3 and 2.
-  #
-  # If `include_self` is true, the current item will also be moved, creating a
-  # gap to the left of the current item:
-  #
-  #   8 . 10 . . . [14] 15 16 17 18 . . 21
-  #                ----------------
-  #
-  # As an optimization, the gap can be precalculated and passed to this method.
-  #
-  # @api private
-  # @raises NoSpaceLeft if the sequence cannot be moved
-  def move_sequence_after(include_self = false, next_gap: find_next_gap_after)
-    raise NoSpaceLeft unless next_gap.present?
-
+  # For example, we have 11 12 13 14 15 21 and the current item is 11
+  # This moves the sequence 12 13 14 15 to 15 16 17 18
+  def move_sequence_after
+    next_gap = find_next_gap_after
     delta = optimum_delta_for_gap(next_gap)
 
-    move_sequence(relative_position, next_gap[:start], delta, include_self)
+    move_sequence(relative_position, next_gap[:start], delta)
   end
 
   private
 
-  def gap_too_small?(pos_a, pos_b)
-    return false unless pos_a && pos_b
-
-    (pos_a - pos_b).abs < MIN_GAP
-  end
-
-  # Find the first suitable gap to the left of the current position.
-  #
-  # Satisfies the relations:
-  #  - gap[:start] <= relative_position
-  #  - abs(gap[:start] - gap[:end]) >= MIN_GAP
-  #  - MIN_POSITION <= gap[:start] <= MAX_POSITION
-  #  - MIN_POSITION <= gap[:end] <= MAX_POSITION
-  #
-  # Supposing that the current item is 13, and we have a sequence of items:
-  #
-  #   1 . . . 5 . . . . 11 12 [13] 14 . . 17
-  #           ^---------^
-  #
-  # Then we return: `{ start: 11, end: 5 }`
-  #
-  # Here start refers to the end of the gap closest to the current item.
+  # Supposing that we have a sequence of items: 1 5 11 12 13 and the current item is 13
+  # This would return: `{ start: 11, end: 5 }`
   def find_next_gap_before
     items_with_next_pos = scoped_items
                             .select('relative_position AS pos, LEAD(relative_position) OVER (ORDER BY relative_position DESC) AS next_pos')
                             .where('relative_position <= ?', relative_position)
                             .order(relative_position: :desc)
 
-    find_next_gap(items_with_next_pos, MIN_POSITION)
-  end
-
-  # Find the first suitable gap to the right of the current position.
-  #
-  # Satisfies the relations:
-  #  - gap[:start] >= relative_position
-  #  - abs(gap[:start] - gap[:end]) >= MIN_GAP
-  #  - MIN_POSITION <= gap[:start] <= MAX_POSITION
-  #  - MIN_POSITION <= gap[:end] <= MAX_POSITION
-  #
-  # Supposing the current item is 13, and that we have a sequence of items:
-  #
-  #   9 . . . [13] 14 15 . . . . 20 . . . 24
-  #                    ^---------^
-  #
-  # Then we return: `{ start: 15, end: 20 }`
-  #
-  # Here start refers to the end of the gap closest to the current item.
+    find_next_gap(items_with_next_pos).tap do |gap|
+      gap[:end] ||= MIN_POSITION
+    end
+  end
+
+  # Supposing that we have a sequence of items: 13 14 15 20 24 and the current item is 13
+  # This would return: `{ start: 15, end: 20 }`
   def find_next_gap_after
     items_with_next_pos = scoped_items
                             .select('relative_position AS pos, LEAD(relative_position) OVER (ORDER BY relative_position ASC) AS next_pos')
                             .where('relative_position >= ?', relative_position)
                             .order(:relative_position)
 
-    find_next_gap(items_with_next_pos, MAX_POSITION)
+    find_next_gap(items_with_next_pos).tap do |gap|
+      gap[:end] ||= MAX_POSITION
+    end
   end
 
-  def find_next_gap(items_with_next_pos, end_is_nil)
-    gap = self.class
-      .from(items_with_next_pos, :items)
-      .where('next_pos IS NULL OR ABS(pos::bigint - next_pos::bigint) >= ?', MIN_GAP)
+  def find_next_gap(items_with_next_pos)
+    gap = self.class.from(items_with_next_pos, :items_with_next_pos)
+                    .where('ABS(pos - next_pos) > 1 OR next_pos IS NULL')
                     .limit(1)
                     .pluck(:pos, :next_pos)
                     .first
 
-    return if gap.nil? || gap.first == end_is_nil
-
-    { start: gap.first, end: gap.second || end_is_nil }
+    { start: gap[0], end: gap[1] }
   end
 
   def optimum_delta_for_gap(gap)
@@ -442,10 +232,9 @@ module RelativePositioning
     [delta, IDEAL_DISTANCE].min
   end
 
-  def move_sequence(start_pos, end_pos, delta, include_self = false)
-    relation = include_self ? scoped_items : relative_siblings
-
-    relation
+  def move_sequence(start_pos, end_pos, delta)
+    scoped_items
+      .where.not(id: self.id)
       .where('relative_position BETWEEN ? AND ?', start_pos, end_pos)
       .update_all("relative_position = relative_position + #{delta}")
   end
@@ -466,10 +255,6 @@ module RelativePositioning
       .first&.last
   end
 
-  def relative_siblings(relation = scoped_items)
-    relation.id_not_in(id)
-  end
-
   def scoped_items
     self.class.relative_positioning_query_base(self)
   end

changelogs/unreleased/ajk-relative-positioning-improvements.yml

----
-title: Performance and robustness improvements for relative positioning
-merge_request: 37724
-author:
-type: performance

ee/app/models/concerns/epic_tree_sorting.rb

@@ -8,8 +8,8 @@ module EpicTreeSorting
   class_methods do
     def relative_positioning_query_base(object)
       from_union([
-        EpicIssue.select("id, relative_position, epic_id as parent_id, epic_id, 'epic_issue' as object_type").in_epic(object.parent_ids),
-        Epic.select("id, relative_position, parent_id, parent_id as epic_id, 'epic' as object_type").where(parent_id: object.parent_ids)
+        EpicIssue.select("id, relative_position, epic_id, 'epic_issue' as object_type").in_epic(object.parent_ids),
+        Epic.select("id, relative_position, parent_id as epic_id, 'epic' as object_type").where(parent_id: object.parent_ids)
       ])
     end
 
@@ -19,14 +19,11 @@ module EpicTreeSorting
   end
 
   included do
-    def move_sequence(start_pos, end_pos, delta, include_self = false)
+    def move_sequence(start_pos, end_pos, delta)
       items_to_update = scoped_items
         .select(:id, :object_type)
         .where('relative_position BETWEEN ? AND ?', start_pos, end_pos)
-
-      unless include_self
-        items_to_update = items_to_update.where.not('object_type = ? AND id = ?', self.class.table_name.singularize, self.id)
-      end
+        .where.not('object_type = ? AND id = ?', self.class.table_name.singularize, self.id)
 
       items_to_update.group_by { |item| item.object_type }.each do |type, group_items|
         ids = group_items.map(&:id)

ee/spec/models/epic_issue_spec.rb

@@ -28,49 +28,9 @@ RSpec.describe EpicIssue do
 
   context "relative positioning" do
     it_behaves_like "a class that supports relative positioning" do
-      let_it_be(:epic) { create(:epic) }
+      let(:epic) { create(:epic) }
       let(:factory) { :epic_issue }
       let(:default_params) { { epic: epic } }
     end
-
-    context 'with a mixed tree level' do
-      let_it_be(:epic) { create(:epic) }
-      let_it_be_with_reload(:left) { create(:epic_issue, epic: epic, relative_position: 100) }
-      let_it_be_with_reload(:middle) { create(:epic, group: epic.group, parent: epic, relative_position: 101) }
-      let_it_be_with_reload(:right) { create(:epic_issue, epic: epic, relative_position: 102) }
-
-      it 'can create space by using move_sequence_after' do
-        left.move_sequence_after
-        [left, middle, right].each(&:reset)
-
-        expect(middle.relative_position - left.relative_position).to be > 1
-        expect(left.relative_position).to be < middle.relative_position
-        expect(middle.relative_position).to be < right.relative_position
-      end
-
-      it 'can create space by using move_sequence_before' do
-        right.move_sequence_before
-        [left, middle, right].each(&:reset)
-
-        expect(right.relative_position - middle.relative_position).to be > 1
-        expect(left.relative_position).to be < middle.relative_position
-        expect(middle.relative_position).to be < right.relative_position
-      end
-
-      it 'moves nulls to the end' do
-        leaves = create_list(:epic_issue, 2, epic: epic, relative_position: nil)
-        nested = create(:epic, group: epic.group, parent: epic, relative_position: nil)
-        moved = [*leaves, nested]
-        level = [nested, *leaves, right]
-
-        expect do
-          EpicIssue.move_nulls_to_end(level)
-        end.not_to change { right.reset.relative_position }
-
-        moved.each(&:reset)
-
-        expect(moved.map(&:relative_position)).to all(be > right.relative_position)
-      end
-    end
   end
 end

ee/spec/models/epic_spec.rb

@@ -616,22 +616,12 @@ RSpec.describe Epic do
   end
 
   context "relative positioning" do
-    context 'there is no parent' do
     it_behaves_like "a class that supports relative positioning" do
       let(:factory) { :epic }
       let(:default_params) { {} }
     end
   end
 
-    context 'there is a parent' do
-      it_behaves_like "a class that supports relative positioning" do
-        let_it_be(:parent) { create(:epic) }
-        let(:factory) { :epic }
-        let(:default_params) { { parent: parent, group: parent.group } }
-      end
-    end
-  end
-
   describe '.related_issues' do
     it 'returns epic issues ordered by relative position' do
       epic1 = create(:epic, group: group)

ee/spec/models/issue_spec.rb

@@ -454,14 +454,20 @@ RSpec.describe Issue do
   end
 
   describe 'relative positioning with group boards' do
-    let_it_be(:group) { create(:group) }
-    let_it_be(:board) { create(:board, group: group) }
-    let_it_be(:project) { create(:project, namespace: group) }
-    let_it_be(:project1) { create(:project, namespace: group) }
-    let_it_be_with_reload(:issue) { create(:issue, project: project) }
-    let_it_be_with_reload(:issue1) { create(:issue, project: project1, relative_position: issue.relative_position + RelativePositioning::IDEAL_DISTANCE) }
+    let(:group) { create(:group) }
+    let!(:board) { create(:board, group: group) }
+    let(:project) { create(:project, namespace: group) }
+    let(:project1) { create(:project, namespace: group) }
+    let(:issue) { build(:issue, project: project) }
+    let(:issue1) { build(:issue, project: project1) }
     let(:new_issue) { build(:issue, project: project1, relative_position: nil) }
 
+    before do
+      [issue, issue1].each do |issue|
+        issue.move_to_end && issue.save
+      end
+    end
+
     describe '#max_relative_position' do
       it 'returns maximum position' do
         expect(issue.max_relative_position).to eq issue1.relative_position
@@ -540,20 +546,18 @@ RSpec.describe Issue do
         issue1.update relative_position: issue.relative_position
 
         new_issue.move_between(issue, issue1)
-        [issue, issue1].each(&:reset)
 
-        expect(new_issue.relative_position)
-          .to be_between(issue.relative_position, issue1.relative_position).exclusive
+        expect(new_issue.relative_position).to be > issue.relative_position
+        expect(issue.relative_position).to be < issue1.relative_position
       end
 
       it 'positions issues between other two if distance is 1' do
         issue1.update relative_position: issue.relative_position + 1
 
         new_issue.move_between(issue, issue1)
-        [issue, issue1].each(&:reset)
 
-        expect(new_issue.relative_position)
-          .to be_between(issue.relative_position, issue1.relative_position).exclusive
+        expect(new_issue.relative_position).to be > issue.relative_position
+        expect(issue.relative_position).to be < issue1.relative_position
       end
 
       it 'positions issue in the middle of other two if distance is big enough' do
@@ -562,20 +566,24 @@ RSpec.describe Issue do
 
         new_issue.move_between(issue, issue1)
 
-        expect(new_issue.relative_position)
-          .to be_between(issue.relative_position, issue1.relative_position).exclusive
+        expect(new_issue.relative_position).to eq(8000)
       end
 
       it 'positions issue closer to the middle if we are at the very top' do
-        new_issue.move_between(nil, issue)
+        issue1.update relative_position: 6000
 
-        expect(new_issue.relative_position).to eq(issue.relative_position - RelativePositioning::IDEAL_DISTANCE)
+        new_issue.move_between(nil, issue1)
+
+        expect(new_issue.relative_position).to eq(6000 - RelativePositioning::IDEAL_DISTANCE)
       end
 
       it 'positions issue closer to the middle if we are at the very bottom' do
-        new_issue.move_between(issue1, nil)
+        issue.update relative_position: 6000
+        issue1.update relative_position: nil
+
+        new_issue.move_between(issue, nil)
 
-        expect(new_issue.relative_position).to eq(issue1.relative_position + RelativePositioning::IDEAL_DISTANCE)
+        expect(new_issue.relative_position).to eq(6000 + RelativePositioning::IDEAL_DISTANCE)
       end
 
       it 'positions issue in the middle of other two if distance is not big enough' do
@@ -592,10 +600,8 @@ RSpec.describe Issue do
         issue1.update relative_position: 101
 
         new_issue.move_between(issue, issue1)
-        [issue, issue1].each(&:reset)
 
-        expect(new_issue.relative_position)
-          .to be_between(issue.relative_position, issue1.relative_position).exclusive
+        expect(new_issue.relative_position).to be_between(issue.relative_position, issue1.relative_position)
       end
 
       it 'uses rebalancing if there is no place' do
@@ -606,15 +612,12 @@ RSpec.describe Issue do
 
         new_issue.move_between(issue1, issue2)
         new_issue.save!
-        [issue, issue1, issue2].each(&:reset)
-
-        expect(new_issue.relative_position)
-          .to be_between(issue1.relative_position, issue2.relative_position).exclusive
 
-        expect([issue, issue1, issue2, new_issue].map(&:relative_position).uniq).to have_attributes(size: 4)
+        expect(new_issue.relative_position).to be_between(issue1.relative_position, issue2.relative_position)
+        expect(issue.reload.relative_position).not_to eq(100)
       end
 
-      it 'positions issue right if we pass non-sequential parameters' do
+      it 'positions issue right if we pass none-sequential parameters' do
         issue.update relative_position: 99
         issue1.update relative_position: 101
         issue2 = create(:issue, relative_position: 102, project: project)

ee/spec/services/epic_issues/create_service_spec.rb

@@ -169,9 +169,7 @@ RSpec.describe EpicIssues::CreateService do
           end
 
           context 'when multiple valid issues are given' do
-            let(:references) { [issue, issue2].map { |i| i.to_reference(full: true) } }
-
-            subject { assign_issue(references) }
+            subject { assign_issue([issue.to_reference(full: true), issue2.to_reference(full: true)]) }
 
             let(:created_link1) { EpicIssue.find_by!(issue_id: issue.id) }
             let(:created_link2) { EpicIssue.find_by!(issue_id: issue2.id) }
@@ -183,18 +181,13 @@ RSpec.describe EpicIssues::CreateService do
               expect(created_link2).to have_attributes(epic: epic)
             end
 
-            it 'places each issue at the start' do
-              subject
-
-              expect(created_link2.relative_position).to be < created_link1.relative_position
-            end
             it 'orders the epic issues to the first place and moves the existing ones down' do
               existing_link = create(:epic_issue, epic: epic, issue: issue3)
 
               subject
 
-              expect([created_link1, created_link2].map(&:relative_position))
-                .to all(be < existing_link.reset.relative_position)
+              expect(created_link2.relative_position).to be < created_link1.relative_position
+              expect(created_link1.relative_position).to be < existing_link.reload.relative_position
             end
 
             it 'returns success status' do

lib/gitlab/database.rb

@@ -22,7 +22,6 @@ module Gitlab
 
     # https://www.postgresql.org/docs/9.2/static/datatype-numeric.html
     MAX_INT_VALUE = 2147483647
-    MIN_INT_VALUE = -2147483648
 
     # The max value between MySQL's TIMESTAMP and PostgreSQL's timestampz:
     # https://www.postgresql.org/docs/9.1/static/datatype-datetime.html

spec/features/boards/issue_ordering_spec.rb

@@ -21,7 +21,7 @@ RSpec.describe 'Issue Boards', :js do
   end
 
   context 'un-ordered issues' do
-    let!(:issue4) { create(:labeled_issue, project: project, labels: [label], relative_position: nil) }
+    let!(:issue4) { create(:labeled_issue, project: project, labels: [label]) }
 
     before do
       visit project_board_path(project, board)

spec/models/analytics/cycle_analytics/project_stage_spec.rb

@@ -23,7 +23,7 @@ RSpec.describe Analytics::CycleAnalytics::ProjectStage do
 
   context 'relative positioning' do
     it_behaves_like 'a class that supports relative positioning' do
-      let_it_be(:project) { create(:project) }
+      let(:project) { build(:project) }
       let(:factory) { :cycle_analytics_project_stage }
       let(:default_params) { { project: project } }
     end

spec/models/issue_spec.rb

@@ -6,7 +6,6 @@ RSpec.describe Issue do
   include ExternalAuthorizationServiceHelpers
 
   let_it_be(:user) { create(:user) }
-  let_it_be(:reusable_project) { create(:project) }
 
   describe "Associations" do
     it { is_expected.to belong_to(:milestone) }
@@ -146,13 +145,13 @@ RSpec.describe Issue do
   end
 
   describe '#order_by_position_and_priority' do
-    let(:project) { reusable_project }
+    let(:project) { create :project }
     let(:p1) { create(:label, title: 'P1', project: project, priority: 1) }
     let(:p2) { create(:label, title: 'P2', project: project, priority: 2) }
     let!(:issue1) { create(:labeled_issue, project: project, labels: [p1]) }
     let!(:issue2) { create(:labeled_issue, project: project, labels: [p2]) }
-    let!(:issue3) { create(:issue, project: project, relative_position: -200) }
-    let!(:issue4) { create(:issue, project: project, relative_position: -100) }
+    let!(:issue3) { create(:issue, project: project, relative_position: 100) }
+    let!(:issue4) { create(:issue, project: project, relative_position: 200) }
 
     it 'returns ordered list' do
       expect(project.issues.order_by_position_and_priority)
@@ -161,10 +160,10 @@ RSpec.describe Issue do
   end
 
   describe '#sort' do
-    let(:project) { reusable_project }
+    let(:project) { create(:project) }
 
     context "by relative_position" do
-      let!(:issue)  { create(:issue, project: project, relative_position: nil) }
+      let!(:issue)  { create(:issue, project: project) }
       let!(:issue2) { create(:issue, project: project, relative_position: 2) }
       let!(:issue3) { create(:issue, project: project, relative_position: 1) }
 
@@ -1028,7 +1027,7 @@ RSpec.describe Issue do
 
   context "relative positioning" do
     it_behaves_like "a class that supports relative positioning" do
-      let_it_be(:project) { create(:project) }
+      let(:project) { create(:project) }
       let(:factory) { :issue }
       let(:default_params) { { project: project } }
     end

spec/support/shared_examples/models/relative_positioning_shared_examples.rb

@@ -25,6 +25,7 @@ RSpec.shared_examples 'a class that supports relative positioning' do
 
       items = [item1, item2, item3]
       described_class.move_nulls_to_end(items)
+      items.map(&:reload)
 
       expect(items.sort_by(&:relative_position)).to eq(items)
       expect(item1.relative_position).to be(1000)
@@ -34,57 +35,22 @@ RSpec.shared_examples 'a class that supports relative positioning' do
       expect(item3.next_relative_position).to be_nil
     end
 
-    it 'preserves relative position' do
-      item1.update!(relative_position: nil)
-      item2.update!(relative_position: nil)
-
-      described_class.move_nulls_to_end([item1, item2])
-
-      expect(item1.relative_position).to be < item2.relative_position
-    end
-
     it 'moves the item near the start position when there are no existing positions' do
       item1.update!(relative_position: nil)
 
       described_class.move_nulls_to_end([item1])
-      expect(item1.reset.relative_position).to eq(described_class::START_POSITION + described_class::IDEAL_DISTANCE)
+      item1.reload
+
+      expect(item1.relative_position).to eq(described_class::START_POSITION + described_class::IDEAL_DISTANCE)
     end
 
     it 'does not perform any moves if all items have their relative_position set' do
       item1.update!(relative_position: 1)
 
-      expect do
       described_class.move_nulls_to_end([item1])
-      end.not_to change { item1.reset.relative_position }
-    end
-
-    it 'manages to move nulls to the end even if there is a sequence at the end' do
-      bunch = create_items_with_positions(run_at_end)
-      item1.update!(relative_position: nil)
-
-      described_class.move_nulls_to_end([item1])
-
-      items = [*bunch, item1]
-      items.each(&:reset)
-
-      expect(items.map(&:relative_position)).to all(be_valid_position)
-      expect(items.sort_by(&:relative_position)).to eq(items)
-    end
-
-    it 'does not have an N+1 issue' do
-      create_items_with_positions(10..12)
-
-      a, b, c, d, e, f = create_items_with_positions([nil, nil, nil, nil, nil, nil])
-
-      baseline = ActiveRecord::QueryRecorder.new do
-        described_class.move_nulls_to_end([a, e])
-      end
-
-      expect { described_class.move_nulls_to_end([b, c, d]) }
-        .not_to exceed_query_limit(baseline)
+      item1.reload
 
-      expect { described_class.move_nulls_to_end([f]) }
-        .not_to exceed_query_limit(baseline.count)
+      expect(item1.relative_position).to be(1)
     end
   end
 
@@ -112,19 +78,11 @@ RSpec.shared_examples 'a class that supports relative positioning' do
       item1.update!(relative_position: nil)
 
       described_class.move_nulls_to_start([item1])
+      item1.reload
 
       expect(item1.relative_position).to eq(described_class::START_POSITION - described_class::IDEAL_DISTANCE)
     end
 
-    it 'preserves relative position' do
-      item1.update!(relative_position: nil)
-      item2.update!(relative_position: nil)
-
-      described_class.move_nulls_to_end([item1, item2])
-
-      expect(item1.relative_position).to be < item2.relative_position
-    end
-
     it 'does not perform any moves if all items have their relative_position set' do
       item1.update!(relative_position: 1)
 
@@ -143,8 +101,8 @@ RSpec.shared_examples 'a class that supports relative positioning' do
 
   describe '#prev_relative_position' do
     it 'returns previous position if there is an item above' do
-      item1.update!(relative_position: 5)
-      item2.update!(relative_position: 15)
+      item1.update(relative_position: 5)
+      item2.update(relative_position: 15)
 
       expect(item2.prev_relative_position).to eq item1.relative_position
     end
@@ -156,8 +114,8 @@ RSpec.shared_examples 'a class that supports relative positioning' do
 
   describe '#next_relative_position' do
     it 'returns next position if there is an item below' do
-      item1.update!(relative_position: 5)
-      item2.update!(relative_position: 15)
+      item1.update(relative_position: 5)
+      item2.update(relative_position: 15)
 
       expect(item1.next_relative_position).to eq item2.relative_position
     end
@@ -167,172 +125,9 @@ RSpec.shared_examples 'a class that supports relative positioning' do
     end
   end
 
-  describe '#find_next_gap_before' do
-    context 'there is no gap' do
-      let(:items) { create_items_with_positions(run_at_start) }
-
-      it 'returns nil' do
-        items.each do |item|
-          expect(item.send(:find_next_gap_before)).to be_nil
-        end
-      end
-    end
-
-    context 'there is a sequence ending at MAX_POSITION' do
-      let(:items) { create_items_with_positions(run_at_end) }
-
-      let(:gaps) do
-        items.map { |item| item.send(:find_next_gap_before) }
-      end
-
-      it 'can find the gap at the start for any item in the sequence' do
-        gap = { start: items.first.relative_position, end: RelativePositioning::MIN_POSITION }
-
-        expect(gaps).to all(eq(gap))
-      end
-
-      it 'respects lower bounds' do
-        gap = { start: items.first.relative_position, end: 10 }
-        new_item.update!(relative_position: 10)
-
-        expect(gaps).to all(eq(gap))
-      end
-    end
-
-    specify do
-      item1.update!(relative_position: 5)
-
-      (0..10).each do |pos|
-        item2.update!(relative_position: pos)
-
-        gap = item2.send(:find_next_gap_before)
-
-        expect(gap[:start]).to be <= item2.relative_position
-        expect((gap[:end] - gap[:start]).abs).to be >= RelativePositioning::MIN_GAP
-        expect(gap[:start]).to be_valid_position
-        expect(gap[:end]).to be_valid_position
-      end
-    end
-
-    it 'deals with there not being any items to the left' do
-      create_items_with_positions([1, 2, 3])
-      new_item.update!(relative_position: 0)
-
-      expect(new_item.send(:find_next_gap_before)).to eq(start: 0, end: RelativePositioning::MIN_POSITION)
-    end
-
-    it 'finds the next gap to the left, skipping adjacent values' do
-      create_items_with_positions([1, 9, 10])
-      new_item.update!(relative_position: 11)
-
-      expect(new_item.send(:find_next_gap_before)).to eq(start: 9, end: 1)
-    end
-
-    it 'finds the next gap to the left' do
-      create_items_with_positions([2, 10])
-
-      new_item.update!(relative_position: 15)
-      expect(new_item.send(:find_next_gap_before)).to eq(start: 15, end: 10)
-
-      new_item.update!(relative_position: 11)
-      expect(new_item.send(:find_next_gap_before)).to eq(start: 10, end: 2)
-
-      new_item.update!(relative_position: 9)
-      expect(new_item.send(:find_next_gap_before)).to eq(start: 9, end: 2)
-
-      new_item.update!(relative_position: 5)
-      expect(new_item.send(:find_next_gap_before)).to eq(start: 5, end: 2)
-    end
-  end
-
-  describe '#find_next_gap_after' do
-    context 'there is no gap' do
-      let(:items) { create_items_with_positions(run_at_end) }
-
-      it 'returns nil' do
-        items.each do |item|
-          expect(item.send(:find_next_gap_after)).to be_nil
-        end
-      end
-    end
-
-    context 'there is a sequence starting at MIN_POSITION' do
-      let(:items) { create_items_with_positions(run_at_start) }
-
-      let(:gaps) do
-        items.map { |item| item.send(:find_next_gap_after) }
-      end
-
-      it 'can find the gap at the end for any item in the sequence' do
-        gap = { start: items.last.relative_position, end: RelativePositioning::MAX_POSITION }
-
-        expect(gaps).to all(eq(gap))
-      end
-
-      it 'respects upper bounds' do
-        gap = { start: items.last.relative_position, end: 10 }
-        new_item.update!(relative_position: 10)
-
-        expect(gaps).to all(eq(gap))
-      end
-    end
-
-    specify do
-      item1.update!(relative_position: 5)
-
-      (0..10).each do |pos|
-        item2.update!(relative_position: pos)
-
-        gap = item2.send(:find_next_gap_after)
-
-        expect(gap[:start]).to be >= item2.relative_position
-        expect((gap[:end] - gap[:start]).abs).to be >= RelativePositioning::MIN_GAP
-        expect(gap[:start]).to be_valid_position
-        expect(gap[:end]).to be_valid_position
-      end
-    end
-
-    it 'deals with there not being any items to the right' do
-      create_items_with_positions([1, 2, 3])
-      new_item.update!(relative_position: 5)
-
-      expect(new_item.send(:find_next_gap_after)).to eq(start: 5, end: RelativePositioning::MAX_POSITION)
-    end
-
-    it 'finds the next gap to the right, skipping adjacent values' do
-      create_items_with_positions([1, 2, 10])
-      new_item.update!(relative_position: 0)
-
-      expect(new_item.send(:find_next_gap_after)).to eq(start: 2, end: 10)
-    end
-
-    it 'finds the next gap to the right' do
-      create_items_with_positions([2, 10])
-
-      new_item.update!(relative_position: 0)
-      expect(new_item.send(:find_next_gap_after)).to eq(start: 0, end: 2)
-
-      new_item.update!(relative_position: 1)
-      expect(new_item.send(:find_next_gap_after)).to eq(start: 2, end: 10)
-
-      new_item.update!(relative_position: 3)
-      expect(new_item.send(:find_next_gap_after)).to eq(start: 3, end: 10)
-
-      new_item.update!(relative_position: 5)
-      expect(new_item.send(:find_next_gap_after)).to eq(start: 5, end: 10)
-    end
-  end
-
   describe '#move_before' do
-    let(:item3) { create(factory, default_params) }
-
     it 'moves item before' do
-      [item2, item1].each do |item|
-        item.move_to_end
-        item.save!
-      end
-
-      expect(item1.relative_position).to be > item2.relative_position
+      [item2, item1].each(&:move_to_end)
 
       item1.move_before(item2)
 
@@ -340,10 +135,12 @@ RSpec.shared_examples 'a class that supports relative positioning' do
     end
 
     context 'when there is no space' do
+      let(:item3) { create(factory, default_params) }
+
       before do
-        item1.update!(relative_position: 1000)
-        item2.update!(relative_position: 1001)
-        item3.update!(relative_position: 1002)
+        item1.update(relative_position: 1000)
+        item2.update(relative_position: 1001)
+        item3.update(relative_position: 1002)
       end
 
       it 'moves items correctly' do
@@ -352,73 +149,6 @@ RSpec.shared_examples 'a class that supports relative positioning' do
         expect(item3.relative_position).to be_between(item1.reload.relative_position, item2.reload.relative_position).exclusive
       end
     end
-
-    it 'can move the item before an item at the start' do
-      item1.update!(relative_position: RelativePositioning::START_POSITION)
-
-      new_item.move_before(item1)
-
-      expect(new_item.relative_position).to be_valid_position
-      expect(new_item.relative_position).to be < item1.reload.relative_position
-    end
-
-    it 'can move the item before an item at MIN_POSITION' do
-      item1.update!(relative_position: RelativePositioning::MIN_POSITION)
-
-      new_item.move_before(item1)
-
-      expect(new_item.relative_position).to be >= RelativePositioning::MIN_POSITION
-      expect(new_item.relative_position).to be < item1.reload.relative_position
-    end
-
-    it 'can move the item before an item bunched up at MIN_POSITION' do
-      item1, item2, item3 = create_items_with_positions(run_at_start)
-
-      new_item.move_before(item3)
-      new_item.save!
-
-      items = [item1, item2, new_item, item3]
-
-      items.each do |item|
-        expect(item.reset.relative_position).to be_valid_position
-      end
-
-      expect(items.sort_by(&:relative_position)).to eq(items)
-    end
-
-    context 'leap-frogging to the left' do
-      before do
-        start = RelativePositioning::START_POSITION
-        item1.update!(relative_position: start - RelativePositioning::IDEAL_DISTANCE * 0)
-        item2.update!(relative_position: start - RelativePositioning::IDEAL_DISTANCE * 1)
-        item3.update!(relative_position: start - RelativePositioning::IDEAL_DISTANCE * 2)
-      end
-
-      let(:item3) { create(factory, default_params) }
-
-      def leap_frog(steps)
-        a = item1
-        b = item2
-
-        steps.times do |i|
-          a.move_before(b)
-          a.save!
-          a, b = b, a
-        end
-      end
-
-      it 'can leap-frog STEPS - 1 times before needing to rebalance' do
-        # This is less efficient than going right, due to the flooring of
-        # integer division
-        expect { leap_frog(RelativePositioning::STEPS - 1) }
-          .not_to change { item3.reload.relative_position }
-      end
-
-      it 'rebalances after leap-frogging STEPS times' do
-        expect { leap_frog(RelativePositioning::STEPS) }
-          .to change { item3.reload.relative_position }
-      end
-    end
   end
 
   describe '#move_after' do
@@ -434,17 +164,9 @@ RSpec.shared_examples 'a class that supports relative positioning' do
       let(:item3) { create(factory, default_params) }
 
       before do
-        item1.update!(relative_position: 1000)
-        item2.update!(relative_position: 1001)
-        item3.update!(relative_position: 1002)
-      end
-
-      it 'can move the item after an item at MAX_POSITION' do
-        item1.update!(relative_position: RelativePositioning::MAX_POSITION)
-
-        new_item.move_after(item1)
-        expect(new_item.relative_position).to be_valid_position
-        expect(new_item.relative_position).to be > item1.reset.relative_position
+        item1.update(relative_position: 1000)
+        item2.update(relative_position: 1001)
+        item3.update(relative_position: 1002)
       end
 
       it 'moves items correctly' do
@@ -453,53 +175,6 @@ RSpec.shared_examples 'a class that supports relative positioning' do
         expect(item1.relative_position).to be_between(item2.reload.relative_position, item3.reload.relative_position).exclusive
       end
     end
-
-    it 'can move the item after an item bunched up at MAX_POSITION' do
-      item1, item2, item3 = create_items_with_positions(run_at_end)
-
-      new_item.move_after(item1)
-      new_item.save!
-
-      items = [item1, new_item, item2, item3]
-
-      items.each do |item|
-        expect(item.reset.relative_position).to be_valid_position
-      end
-
-      expect(items.sort_by(&:relative_position)).to eq(items)
-    end
-
-    context 'leap-frogging' do
-      before do
-        start = RelativePositioning::START_POSITION
-        item1.update!(relative_position: start + RelativePositioning::IDEAL_DISTANCE * 0)
-        item2.update!(relative_position: start + RelativePositioning::IDEAL_DISTANCE * 1)
-        item3.update!(relative_position: start + RelativePositioning::IDEAL_DISTANCE * 2)
-      end
-
-      let(:item3) { create(factory, default_params) }
-
-      def leap_frog(steps)
-        a = item1
-        b = item2
-
-        steps.times do |i|
-          a.move_after(b)
-          a.save!
-          a, b = b, a
-        end
-      end
-
-      it 'can leap-frog STEPS times before needing to rebalance' do
-        expect { leap_frog(RelativePositioning::STEPS) }
-          .not_to change { item3.reload.relative_position }
-      end
-
-      it 'rebalances after leap-frogging STEPS+1 times' do
-        expect { leap_frog(RelativePositioning::STEPS + 1) }
-          .to change { item3.reload.relative_position }
-      end
-    end
   end
 
   describe '#move_to_end' do
@@ -518,17 +193,8 @@ RSpec.shared_examples 'a class that supports relative positioning' do
 
   describe '#move_between' do
     before do
-      [item1, item2].each do |item|
-        item.move_to_end && item.save!
-      end
-    end
-
-    shared_examples 'moves item between' do
-      it 'moves the middle item to between left and right' do
-        expect do
-          middle.move_between(left, right)
-          middle.save!
-        end.to change { between_exclusive?(left, middle, right) }.from(false).to(true)
+      [item1, item2].each do |item1|
+        item1.move_to_end && item1.save
       end
     end
 
@@ -552,26 +218,26 @@ RSpec.shared_examples 'a class that supports relative positioning' do
     end
 
     it 'positions items even when after and before positions are the same' do
-      item2.update! relative_position: item1.relative_position
+      item2.update relative_position: item1.relative_position
 
       new_item.move_between(item1, item2)
-      [item1, item2].each(&:reset)
 
       expect(new_item.relative_position).to be > item1.relative_position
       expect(item1.relative_position).to be < item2.relative_position
     end
 
-    context 'the two items are next to each other' do
-      let(:left) { item1 }
-      let(:middle) { new_item }
-      let(:right) { create_item(relative_position: item1.relative_position + 1) }
+    it 'positions items between other two if distance is 1' do
+      item2.update relative_position: item1.relative_position + 1
+
+      new_item.move_between(item1, item2)
 
-      it_behaves_like 'moves item between'
+      expect(new_item.relative_position).to be > item1.relative_position
+      expect(item1.relative_position).to be < item2.relative_position
     end
 
     it 'positions item in the middle of other two if distance is big enough' do
-      item1.update! relative_position: 6000
-      item2.update! relative_position: 10000
+      item1.update relative_position: 6000
+      item2.update relative_position: 10000
 
       new_item.move_between(item1, item2)
 
@@ -579,8 +245,7 @@ RSpec.shared_examples 'a class that supports relative positioning' do
     end
 
     it 'positions item closer to the middle if we are at the very top' do
-      item1.update!(relative_position: 6001)
-      item2.update!(relative_position: 6000)
+      item2.update relative_position: 6000
 
       new_item.move_between(nil, item2)
 
@@ -588,53 +253,51 @@ RSpec.shared_examples 'a class that supports relative positioning' do
     end
 
     it 'positions item closer to the middle if we are at the very bottom' do
-      new_item.update!(relative_position: 1)
-      item1.update!(relative_position: 6000)
-      item2.update!(relative_position: 5999)
+      new_item.update relative_position: 1
+      item1.update relative_position: 6000
+      item2.destroy
 
       new_item.move_between(item1, nil)
 
       expect(new_item.relative_position).to eq(6000 + RelativePositioning::IDEAL_DISTANCE)
     end
 
-    it 'positions item in the middle of other two' do
-      item1.update! relative_position: 100
-      item2.update! relative_position: 400
+    it 'positions item in the middle of other two if distance is not big enough' do
+      item1.update relative_position: 100
+      item2.update relative_position: 400
 
       new_item.move_between(item1, item2)
 
       expect(new_item.relative_position).to eq(250)
     end
 
-    context 'there is no space' do
-      let(:middle) { new_item }
-      let(:left) { create_item(relative_position: 100) }
-      let(:right) { create_item(relative_position: 101) }
+    it 'positions item in the middle of other two is there is no place' do
+      item1.update relative_position: 100
+      item2.update relative_position: 101
 
-      it_behaves_like 'moves item between'
-    end
+      new_item.move_between(item1, item2)
 
-    context 'there is a bunch of items' do
-      let(:items) { create_items_with_positions(100..104) }
-      let(:left) { items[1] }
-      let(:middle) { items[3] }
-      let(:right) { items[2] }
+      expect(new_item.relative_position).to be_between(item1.relative_position, item2.relative_position).exclusive
+    end
 
-      it_behaves_like 'moves item between'
+    it 'uses rebalancing if there is no place' do
+      item1.update relative_position: 100
+      item2.update relative_position: 101
+      item3 = create_item(relative_position: 102)
+      new_item.update relative_position: 103
 
-      it 'handles bunches correctly' do
-        middle.move_between(left, right)
-        middle.save!
+      new_item.move_between(item2, item3)
+      new_item.save!
 
-        expect(items.first.reset.relative_position).to be < middle.relative_position
-      end
+      expect(new_item.relative_position).to be_between(item2.relative_position, item3.relative_position).exclusive
+      expect(item1.reload.relative_position).not_to eq(100)
     end
 
-    it 'positions item right if we pass non-sequential parameters' do
-      item1.update! relative_position: 99
-      item2.update! relative_position: 101
+    it 'positions item right if we pass none-sequential parameters' do
+      item1.update relative_position: 99
+      item2.update relative_position: 101
       item3 = create_item(relative_position: 102)
-      new_item.update! relative_position: 103
+      new_item.update relative_position: 103
 
       new_item.move_between(item1, item3)
       new_item.save!
@@ -666,12 +329,6 @@ RSpec.shared_examples 'a class that supports relative positioning' do
       expect(positions).to eq([90, 95, 96, 102])
     end
 
-    it 'raises an error if there is no space' do
-      items = create_items_with_positions(run_at_start)
-
-      expect { items.last.move_sequence_before }.to raise_error(RelativePositioning::NoSpaceLeft)
-    end
-
     it 'finds a gap if there are unused positions' do
       items = create_items_with_positions([100, 101, 102])
 
@@ -679,8 +336,7 @@ RSpec.shared_examples 'a class that supports relative positioning' do
       items.last.save!
 
       positions = items.map { |item| item.reload.relative_position }
-
-      expect(positions.last - positions.second).to be > RelativePositioning::MIN_GAP
+      expect(positions).to eq([50, 51, 102])
     end
   end
 
@@ -702,33 +358,7 @@ RSpec.shared_examples 'a class that supports relative positioning' do
       items.first.save!
 
       positions = items.map { |item| item.reload.relative_position }
-      expect(positions.second - positions.first).to be > RelativePositioning::MIN_GAP
+      expect(positions).to eq([100, 601, 602])
     end
-
-    it 'raises an error if there is no space' do
-      items = create_items_with_positions(run_at_end)
-
-      expect { items.first.move_sequence_after }.to raise_error(RelativePositioning::NoSpaceLeft)
-    end
-  end
-
-  def be_valid_position
-    be_between(RelativePositioning::MIN_POSITION, RelativePositioning::MAX_POSITION)
-  end
-
-  def between_exclusive?(left, middle, right)
-    a, b, c = [left, middle, right].map { |item| item.reset.relative_position }
-    return false if a.nil? || b.nil?
-    return a < b if c.nil?
-
-    a < b && b < c
-  end
-
-  def run_at_end(size = 3)
-    (RelativePositioning::MAX_POSITION - size)..RelativePositioning::MAX_POSITION
-  end
-
-  def run_at_start(size = 3)
-    (RelativePositioning::MIN_POSITION..).take(size)
   end
 end