diff options
Diffstat (limited to 'lib/gitlab/background_migration/batching_strategies/loose_index_scan_batching_strategy.rb')
-rw-r--r-- | lib/gitlab/background_migration/batching_strategies/loose_index_scan_batching_strategy.rb | 37 |
1 files changed, 37 insertions, 0 deletions
diff --git a/lib/gitlab/background_migration/batching_strategies/loose_index_scan_batching_strategy.rb b/lib/gitlab/background_migration/batching_strategies/loose_index_scan_batching_strategy.rb new file mode 100644 index 00000000000..5cad9d2e3c4 --- /dev/null +++ b/lib/gitlab/background_migration/batching_strategies/loose_index_scan_batching_strategy.rb @@ -0,0 +1,37 @@ +# frozen_string_literal: true + +module Gitlab + module BackgroundMigration + module BatchingStrategies + # This strategy provides an efficient way to iterate over columns with non-distinct values. + # A common use case would be iterating over a foreign key columns, for example issues.project_id + class LooseIndexScanBatchingStrategy < BaseStrategy + include Gitlab::Database::DynamicModelHelpers + + # Finds and returns the next batch in the table. + # + # table_name - The table to batch over + # column_name - The column to batch over + # batch_min_value - The minimum value which the next batch will start at + # batch_size - The size of the next batch + # job_arguments - The migration job arguments + # job_class - The migration job class + def next_batch(table_name, column_name, batch_min_value:, batch_size:, job_arguments:, job_class: nil) + model_class = define_batchable_model(table_name, connection: connection) + + quoted_column_name = model_class.connection.quote_column_name(column_name) + relation = model_class.where("#{quoted_column_name} >= ?", batch_min_value) + next_batch_bounds = nil + + relation.distinct_each_batch(of: batch_size, column: column_name) do |batch| # rubocop:disable Lint/UnreachableLoop + next_batch_bounds = batch.pluck(Arel.sql("MIN(#{quoted_column_name}), MAX(#{quoted_column_name})")).first + + break + end + + next_batch_bounds + end + end + end + end +end |