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class EnqueueDeleteDiffFilesWorkers < ActiveRecord::Migration
include Gitlab::Database::MigrationHelpers
class MergeRequestDiff < ActiveRecord::Base
self.table_name = 'merge_request_diffs'
belongs_to :merge_request
include EachBatch
end
DOWNTIME = false
BATCH_SIZE = 1000
MIGRATION = 'DeleteDiffFiles'
DELAY_INTERVAL = 8.minutes
TMP_INDEX = 'tmp_partial_diff_id_with_files_index'.freeze
disable_ddl_transaction!
def up
# We add temporary index, to make iteration over batches more performant.
# Conditional here is to avoid the need of doing that in a separate
# migration file to make this operation idempotent.
#
unless index_exists_by_name?(:merge_request_diffs, TMP_INDEX)
add_concurrent_index(:merge_request_diffs, :id, where: "(state NOT IN ('without_files', 'empty'))", name: TMP_INDEX)
end
diffs_with_files = MergeRequestDiff.where.not(state: ['without_files', 'empty'])
# explain (analyze, buffers) example for the iteration:
#
# Index Only Scan using tmp_index_20013 on merge_request_diffs (cost=0.43..1630.19 rows=60567 width=4) (actual time=0.047..9.572 rows=56976 loops=1)
# Index Cond: ((id >= 764586) AND (id < 835298))
# Heap Fetches: 8
# Buffers: shared hit=18188
# Planning time: 0.752 ms
# Execution time: 12.430 ms
#
diffs_with_files.each_batch(of: BATCH_SIZE) do |relation, outer_index|
ids = relation.pluck(:id)
ids.each_with_index do |diff_id, inner_index|
# This will give some space between batches of workers.
interval = DELAY_INTERVAL * outer_index + inner_index.minutes
# A single `merge_request_diff` can be associated with way too many
# `merge_request_diff_files`. It's better to avoid batching these and
# schedule one at a time.
#
# Considering roughly 6M jobs, this should take ~30 days to process all
# of them.
#
BackgroundMigrationWorker.perform_in(interval, MIGRATION, [diff_id])
end
end
# We remove temporary index, because it is not required during standard
# operations and runtime.
#
remove_concurrent_index_by_name(:merge_request_diffs, TMP_INDEX)
end
def down
if index_exists_by_name?(:merge_request_diffs, TMP_INDEX)
remove_concurrent_index_by_name(:merge_request_diffs, TMP_INDEX)
end
end
end
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