diff options
Diffstat (limited to 'app/models/concerns/relative_positioning.rb')
| -rw-r--r-- | app/models/concerns/relative_positioning.rb | 141 |
1 files changed, 100 insertions, 41 deletions
diff --git a/app/models/concerns/relative_positioning.rb b/app/models/concerns/relative_positioning.rb index 22b6b1d720c..6d3c7a7ed68 100644 --- a/app/models/concerns/relative_positioning.rb +++ b/app/models/concerns/relative_positioning.rb @@ -1,5 +1,26 @@ # frozen_string_literal: true +# This module makes it possible to handle items as a list, where the order of items can be easily altered +# Requirements: +# +# - 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) +# +# Setup like this in the body of your class: +# +# include RelativePositioning +# +# # base query used for the position calculation +# def self.relative_positioning_query_base(issue) +# where(deleted: false) +# end +# +# # column that should be used in GROUP BY +# def self.relative_positioning_parent_column +# :project_id +# end +# module RelativePositioning extend ActiveSupport::Concern @@ -8,12 +29,8 @@ module RelativePositioning MAX_POSITION = Gitlab::Database::MAX_INT_VALUE IDEAL_DISTANCE = 500 - included do - after_save :save_positionable_neighbours - end - class_methods do - def move_to_end(objects) + def move_nulls_to_end(objects) objects = objects.reject(&:relative_position) return if objects.empty? @@ -22,7 +39,7 @@ module RelativePositioning self.transaction do objects.each do |object| - relative_position = position_between(max_relative_position, MAX_POSITION) + relative_position = position_between(max_relative_position || START_POSITION, MAX_POSITION) object.relative_position = relative_position max_relative_position = relative_position object.save(touch: false) @@ -93,11 +110,12 @@ module RelativePositioning return move_after(before) unless after return move_before(after) unless before - # If there is no place to insert an issue we need to create one by moving the before issue closer - # to its predecessor. This process will recursively move all the predecessors until we have a place + # 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 if (after.relative_position - before.relative_position) < 2 - before.move_before - @positionable_neighbours = [before] # rubocop:disable Gitlab/ModuleWithInstanceVariables + after.move_sequence_before + before.reset end self.relative_position = self.class.position_between(before.relative_position, after.relative_position) @@ -107,12 +125,8 @@ module RelativePositioning pos_before = before.relative_position pos_after = before.next_relative_position - if before.shift_after? - issue_to_move = self.class.in_parents(parent_ids).find_by!(relative_position: pos_after) - issue_to_move.move_after - @positionable_neighbours = [issue_to_move] # rubocop:disable Gitlab/ModuleWithInstanceVariables - - pos_after = issue_to_move.relative_position + if pos_after && (pos_after - pos_before) < 2 + before.move_sequence_after end self.relative_position = self.class.position_between(pos_before, pos_after) @@ -122,12 +136,8 @@ module RelativePositioning pos_after = after.relative_position pos_before = after.prev_relative_position - if after.shift_before? - issue_to_move = self.class.in_parents(parent_ids).find_by!(relative_position: pos_before) - issue_to_move.move_before - @positionable_neighbours = [issue_to_move] # rubocop:disable Gitlab/ModuleWithInstanceVariables - - pos_before = issue_to_move.relative_position + if pos_before && (pos_after - pos_before) < 2 + after.move_sequence_before end self.relative_position = self.class.position_between(pos_before, pos_after) @@ -141,46 +151,95 @@ module RelativePositioning self.relative_position = self.class.position_between(min_relative_position || START_POSITION, MIN_POSITION) end - # Indicates if there is an issue that should be shifted to free the place - def shift_after? - next_pos = next_relative_position - next_pos && (next_pos - relative_position) == 1 + # Moves the sequence before the current item to the middle of the next gap + # 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) end - # Indicates if there is an issue that should be shifted to free the place - def shift_before? - prev_pos = prev_relative_position - prev_pos && (relative_position - prev_pos) == 1 + # Moves the sequence after the current item to the middle of the next gap + # 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) end private - # rubocop:disable Gitlab/ModuleWithInstanceVariables - def save_positionable_neighbours - return unless @positionable_neighbours + # 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).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) - status = @positionable_neighbours.all? { |issue| issue.save(touch: false) } - @positionable_neighbours = nil + find_next_gap(items_with_next_pos).tap do |gap| + gap[:end] ||= MAX_POSITION + end + end + + 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 + + { start: gap[0], end: gap[1] } + end - status + def optimum_delta_for_gap(gap) + delta = ((gap[:start] - gap[:end]) / 2.0).abs.ceil + + [delta, IDEAL_DISTANCE].min + end + + 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 - # rubocop:enable Gitlab/ModuleWithInstanceVariables def calculate_relative_position(calculation) # When calculating across projects, this is much more efficient than # MAX(relative_position) without the GROUP BY, due to index usage: # https://gitlab.com/gitlab-org/gitlab-ce/issues/54276#note_119340977 - relation = self.class - .in_parents(parent_ids) + relation = scoped_items .order(Gitlab::Database.nulls_last_order('position', 'DESC')) + .group(self.class.relative_positioning_parent_column) .limit(1) - .group(self.class.parent_column) relation = yield relation if block_given? relation - .pluck(self.class.parent_column, "#{calculation}(relative_position) AS position") + .pluck(self.class.relative_positioning_parent_column, Arel.sql("#{calculation}(relative_position) AS position")) .first&. last end + + def scoped_items + self.class.relative_positioning_query_base(self) + end end |