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# frozen_string_literal: true
class RemoveOrphanedLabelLinks < ActiveRecord::Migration[4.2]
include Gitlab::Database::MigrationHelpers
DOWNTIME = false
disable_ddl_transaction!
class LabelLinks < ActiveRecord::Base
self.table_name = 'label_links'
include EachBatch
def self.orphaned
where('NOT EXISTS ( SELECT 1 FROM labels WHERE labels.id = label_links.label_id )')
end
end
def up
# Some of these queries can take up to 10 seconds to run on GitLab.com,
# which is pretty close to our 15 second statement timeout. To ensure a
# smooth deployment procedure we disable the statement timeouts for this
# migration, just in case.
disable_statement_timeout do
# On GitLab.com there are over 2,000,000 orphaned label links. On
# staging, removing 100,000 rows generated a max replication lag of 6.7
# MB. In total, removing all these rows will only generate about 136 MB
# of data, so it should be safe to do this.
LabelLinks.orphaned.each_batch(of: 100_000) do |batch|
batch.delete_all
end
end
add_concurrent_foreign_key(:label_links, :labels, column: :label_id, on_delete: :cascade)
end
def down
# There is no way to restore orphaned label links.
if foreign_key_exists?(:label_links, column: :label_id)
remove_foreign_key(:label_links, column: :label_id)
end
end
end
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