50 lines
1.7 KiB
Ruby
50 lines
1.7 KiB
Ruby
# frozen_string_literal: true
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module Gitlab
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module BackgroundMigration
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# Background migration that updates the value of one or more
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# columns using the value of other columns in the same table.
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#
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# - The {start_id, end_id} arguments are at the start so that it can be used
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# with `queue_batched_background_migration`
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# - Uses sub-batching so that we can keep each update's execution time at
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# low 100s ms, while being able to update more records per 2 minutes
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# that we allow background migration jobs to be scheduled one after the other
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# - We skip the NULL checks as they may result in not using an index scan
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# - The table that is migrated does _not_ need `id` as the primary key
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# We use the provided primary_key column to perform the update.
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class CopyColumnUsingBackgroundMigrationJob < BatchedMigrationJob
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job_arguments :copy_from, :copy_to
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operation_name :update_all
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def perform
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assignment_clauses = build_assignment_clauses(copy_from, copy_to)
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each_sub_batch do |relation|
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relation.update_all(assignment_clauses)
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end
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end
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private
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def build_assignment_clauses(copy_from, copy_to)
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copy_from = Array.wrap(copy_from)
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copy_to = Array.wrap(copy_to)
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unless copy_from.count == copy_to.count
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raise ArgumentError, 'number of source and destination columns must match'
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end
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assignments = copy_from.zip(copy_to).map do |from_column, to_column|
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from_column = connection.quote_column_name(from_column)
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to_column = connection.quote_column_name(to_column)
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"#{to_column} = #{from_column}"
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end
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assignments.join(', ')
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end
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end
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end
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end
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