42 lines
1.6 KiB
Ruby
42 lines
1.6 KiB
Ruby
# frozen_string_literal: true
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module Gitlab
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module BackgroundMigration
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# CopyColumn is a simple (reusable) background migration that can be used to
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# update the value of a column based on the value of another column in the
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# same table.
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#
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# For this background migration to work the table that is migrated _has_ to
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# have an `id` column as the primary key.
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class CopyColumn
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# table - The name of the table that contains the columns.
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# copy_from - The column containing the data to copy.
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# copy_to - The column to copy the data to.
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# start_id - The start ID of the range of rows to update.
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# end_id - The end ID of the range of rows to update.
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def perform(table, copy_from, copy_to, start_id, end_id)
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return unless connection.column_exists?(table, copy_to)
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quoted_table = connection.quote_table_name(table)
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quoted_copy_from = connection.quote_column_name(copy_from)
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quoted_copy_to = connection.quote_column_name(copy_to)
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# We're using raw SQL here since this job may be frequently executed. As
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# a result dynamically defining models would lead to many unnecessary
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# schema information queries.
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connection.execute <<-SQL.strip_heredoc
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UPDATE #{quoted_table}
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SET #{quoted_copy_to} = #{quoted_copy_from}
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WHERE id BETWEEN #{start_id} AND #{end_id}
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AND #{quoted_copy_from} IS NOT NULL
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AND #{quoted_copy_to} IS NULL
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SQL
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end
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def connection
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ActiveRecord::Base.connection
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end
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end
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end
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end
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