Delete conflicting redirects in background

db/post_migrate/20170907170235_delete_conflicting_redirect_routes.rb

+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class DeleteConflictingRedirectRoutes < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  BATCH_SIZE = 1000 # Number of rows to process per job
+  JOB_BUFFER_SIZE = 1000 # Number of jobs to bulk queue at a time
+  MIGRATION = 'DeleteConflictingRedirectRoutes'.freeze
+
+  disable_ddl_transaction!
+
+  class Route < ActiveRecord::Base
+    include EachBatch
+
+    self.table_name = 'routes'
+  end
+
+  def up
+    jobs = []
+
+    say opening_message
+
+    queue_background_migration_jobs(Route, MIGRATION)
+  end
+
+  def down
+    # nothing
+  end
+
+  def opening_message
+    <<~MSG
+      Clean up redirect routes that conflict with regular routes.
+         See initial bug fix:
+         https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/13357
+    MSG
+  end
+
+  def queue_background_migration_jobs(model_class, job_class_name, batch_size = BATCH_SIZE)
+    jobs = []
+
+    model_class.each_batch(of: batch_size) do |relation|
+      start_id, end_id = relation.pluck('MIN(id), MAX(id)').first
+
+      # Note: This conditional will only be true if JOB_BUFFER_SIZE * batch_size < (total number of rows)
+      if jobs.length >= JOB_BUFFER_SIZE
+        # We push multiple jobs at a time to reduce the time spent in
+        # Sidekiq/Redis operations. We're using this buffer based approach so we
+        # don't need to run additional queries for every range.
+        bulk_queue_jobs(jobs)
+        jobs.clear
+      end
+
+      jobs << [job_class_name, [start_id, end_id]]
+    end
+
+    bulk_queue_jobs(jobs) unless jobs.empty?
+  end
+
+  def bulk_queue_jobs(jobs)
+    say "Queuing #{jobs.size} BackgroundMigrationWorker jobs..."
+
+    BackgroundMigrationWorker.perform_bulk(jobs)
+  end
+end

lib/gitlab/background_migration/delete_conflicting_redirect_routes.rb

+module Gitlab
+  module BackgroundMigration
+    class DeleteConflictingRedirectRoutes
+      class Route < ActiveRecord::Base
+        self.table_name = 'routes'
+      end
+
+      class RedirectRoute < ActiveRecord::Base
+        self.table_name = 'redirect_routes'
+      end
+
+      # start_id - The start ID of the range of events to process
+      # end_id - The end ID of the range to process.
+      def perform(start_id, end_id)
+        return unless migrate?
+
+        conflicts = RedirectRoute.where(routes_match_redirects_clause(start_id, end_id))
+        num_rows = conflicts.delete_all
+
+        Rails.logger.info("Gitlab::BackgroundMigration::DeleteConflictingRedirectRoutes [#{start_id}, #{end_id}] - Deleted #{num_rows} redirect routes that were conflicting with routes.")
+      end
+
+      def migrate?
+        Route.table_exists? && RedirectRoute.table_exists?
+      end
+
+      def routes_match_redirects_clause(start_id, end_id)
+        <<~ROUTES_MATCH_REDIRECTS
+          EXISTS (
+            SELECT 1 FROM routes
+            WHERE (#{route_paths_match_redirects})
+            AND routes.id BETWEEN #{start_id} AND #{end_id}
+          )
+        ROUTES_MATCH_REDIRECTS
+      end
+
+      def route_paths_match_redirects
+        if Gitlab::Database.postgresql?
+          <<~ROUTE_PATHS_MATCH_REDIRECTS
+            LOWER(redirect_routes.path) = LOWER(routes.path)
+            OR LOWER(redirect_routes.path) LIKE LOWER(CONCAT(routes.path, '/%'))
+          ROUTE_PATHS_MATCH_REDIRECTS
+        else
+          <<~ROUTE_PATHS_MATCH_REDIRECTS
+            redirect_routes.path = routes.path
+            OR redirect_routes.path LIKE CONCAT(routes.path, '/%')
+          ROUTE_PATHS_MATCH_REDIRECTS
+        end
+      end
+    end
+  end
+end