Avoid title length overflows

- More terse deletion logic

db/migrate/20200305082754_remove_duplicate_labels_from_project.rb

@@ -70,19 +70,20 @@ WITH data AS (
       # create backup records
       BackupLabel.insert_all!(duplicate_labels.map { |label| label.except("row_number") })
 
-      ApplicationRecord.connection.execute(<<-SQL.squish)
-DELETE FROM labels
-WHERE labels.id IN (#{duplicate_labels.map { |dup| dup["id"] }.join(", ")});
-      SQL
+      Label.where(id: duplicate_labels.pluck("id")).delete_all
     end
   end
 
   def rename_partial_duplicates(start_id, stop_id)
+    # We need to ensure that the new title (with `_duplicate#{ID}`) doesn't exceed the limit.
+    # Truncate the original title (if needed) to 245 characters minus the length of the ID
+    # then add `_duplicate#{ID}`
+
     soft_duplicates = ApplicationRecord.connection.execute(<<-SQL.squish)
 WITH data AS (
   SELECT
      *,
-     title || '_' || 'duplicate' || id AS new_title,
+     substring(title from 1 for 245 - length(id::text)) || '_duplicate' || id::text as new_title,
      #{RENAME} AS restore_action,
      row_number() OVER (PARTITION BY project_id, title ORDER BY id) AS row_number
   FROM labels
@@ -95,7 +96,7 @@ WITH data AS (
       BackupLabel.insert_all!(soft_duplicates.map { |label| label.except("row_number") })
 
       ApplicationRecord.connection.execute(<<-SQL.squish)
-UPDATE labels SET title = title || '_' || 'duplicate' || extract(epoch from now())
+UPDATE labels SET title = substring(title from 1 for 245 - length(id::text)) || '_duplicate' || id::text
 WHERE labels.id IN (#{soft_duplicates.map { |dup| dup["id"] }.join(", ")});
       SQL
     end

doc/user/project/labels.md

@@ -259,7 +259,7 @@ Ties are broken arbitrarily.
 In specific circumstances it was possible to create labels with duplicate titles in the same
 namespace.
 
-To resolve the duplication, [in GitLab 13.0](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/21384)
+To resolve the duplication, [in GitLab 13.1](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/21384)
 and later, some duplicate labels have `_duplicate<number>` appended to their titles.
 
 You can safely change these labels' titles if you prefer.

spec/migrations/remove_duplicate_labels_from_project_spec.rb

@@ -198,8 +198,8 @@ describe RemoveDuplicateLabelsFromProject do
       it 'modifies the titles of the partial duplicates' do
         migration.up
 
-        expect(second_label.reload.title).to match(/#{label_title}_duplicate/)
-        expect(fourth_label.reload.title).to match(/#{other_title}_duplicate/)
+        expect(second_label.reload.title).to match(/#{label_title}_duplicate#{second_label.id}$/)
+        expect(fourth_label.reload.title).to match(/#{other_title}_duplicate#{fourth_label.id}$/)
       end
 
       it 'restores renamed records on rollback' do
@@ -213,6 +213,22 @@ describe RemoveDuplicateLabelsFromProject do
         expect(second_label.reload.attributes).to include(second_label_attributes)
         expect(fourth_label.reload.attributes).to include(fourth_label_attributes)
       end
+
+      context 'when the labels have a long title that might overflow' do
+        let(:long_title) { "a" * 255 }
+
+        before do
+          first_label.update_attribute(:title, long_title)
+          second_label.update_attribute(:title, long_title)
+        end
+
+        it 'keeps the length within the limit' do
+          migration.up
+
+          expect(second_label.reload.title).to eq("#{"a" * 244}_duplicate#{second_label.id}")
+          expect(second_label.title.length).to eq 255
+        end
+      end
     end
   end