38 lines
1.5 KiB
Ruby
38 lines
1.5 KiB
Ruby
# frozen_string_literal: true
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module Gitlab
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module BackgroundMigration
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module BatchingStrategies
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# This strategy provides an efficient way to iterate over columns with non-distinct values.
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# A common use case would be iterating over a foreign key columns, for example issues.project_id
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class LooseIndexScanBatchingStrategy < BaseStrategy
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include Gitlab::Database::DynamicModelHelpers
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# Finds and returns the next batch in the table.
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#
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# table_name - The table to batch over
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# column_name - The column to batch over
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# batch_min_value - The minimum value which the next batch will start at
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# batch_size - The size of the next batch
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# job_arguments - The migration job arguments
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# job_class - The migration job class
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def next_batch(table_name, column_name, batch_min_value:, batch_size:, job_arguments:, job_class: nil)
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model_class = define_batchable_model(table_name, connection: connection)
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quoted_column_name = model_class.connection.quote_column_name(column_name)
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relation = model_class.where("#{quoted_column_name} >= ?", batch_min_value)
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next_batch_bounds = nil
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relation.distinct_each_batch(of: batch_size, column: column_name) do |batch| # rubocop:disable Lint/UnreachableLoop
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next_batch_bounds = batch.pick(Arel.sql("MIN(#{quoted_column_name}), MAX(#{quoted_column_name})"))
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break
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end
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next_batch_bounds
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end
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end
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end
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end
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end
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