Merge branch '18915-pagination-with-priority-sort-repeats-results' into 'master'
Fix pagination on sorts with lots of ties ## What does this MR do? Fixes #18915. As we only order by the sorted column, we don't have any tie-breaker. Some orderings, like priority and weight, have lots of ties, so you can see duplicate results as you page through. (Timestamp columns are less susceptible to this.) ## Are there points in the code the reviewer needs to double check? I just picked `id DESC`, this could as easily be `id ASC`. ## Why was this MR needed? Postgres and MySQL don't guarantee that pagination with `LIMIT` and `OFFSET` will work as expected if the ordering isn't unique. From the Postgres docs: > When using `LIMIT`, it is important to use an `ORDER BY` clause that > constrains the result rows into a unique order. Otherwise you will get > an unpredictable subset of the query's rows Before: [1] pry(main)> issues = 1.upto(Issue.count).map { |i| Issue.sort('priority').page(i).per(1).map(&:id) }.flatten [2] pry(main)> issues.count => 81 [3] pry(main)> issues.uniq.count => 42 After: [1] pry(main)> issues = 1.upto(Issue.count).map { |i| Issue.sort('priority').page(i).per(1).map(&:id) }.flatten [2] pry(main)> issues.count => 81 [3] pry(main)> issues.uniq.count => 81 See merge request !4878
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commit
26b9577719
3 changed files with 27 additions and 9 deletions
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@ -4,6 +4,7 @@ v 8.10.0 (unreleased)
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- Wrap code blocks on Activies and Todos page. !4783 (winniehell)
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- Add Sidekiq queue duration to transaction metrics.
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- Fix MR-auto-close text added to description. !4836
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- Fix pagination when sorting by columns with lots of ties (like priority)
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- Implement Subresource Integrity for CSS and JavaScript assets. This prevents malicious assets from loading in the case of a CDN compromise.
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v 8.9.1
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@ -112,7 +112,7 @@ module Issuable
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end
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def sort(method, excluded_labels: [])
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case method.to_s
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sorted = case method.to_s
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when 'milestone_due_asc' then order_milestone_due_asc
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when 'milestone_due_desc' then order_milestone_due_desc
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when 'downvotes_desc' then order_downvotes_desc
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@ -121,6 +121,9 @@ module Issuable
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else
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order_by(method)
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end
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# Break ties with the ID column for pagination
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sorted.order(id: :desc)
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end
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def order_labels_priority(excluded_labels: [])
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@ -154,6 +154,20 @@ describe Issue, "Issuable" do
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expect(issues).to match_array([issue1, issue2, issue, issue3])
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end
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end
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context 'when all of the results are level on the sort key' do
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let!(:issues) do
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10.times { create(:issue, project: project) }
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end
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it 'has no duplicates across pages' do
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sorted_issue_ids = 1.upto(10).map do |i|
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project.issues.sort('milestone_due_desc').page(i).per(1).first.id
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end
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expect(sorted_issue_ids).to eq(sorted_issue_ids.uniq)
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end
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end
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end
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