142 lines
4.7 KiB
Ruby
142 lines
4.7 KiB
Ruby
module Gitlab
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module Database
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module MigrationHelpers
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# Creates a new index, concurrently when supported
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#
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# On PostgreSQL this method creates an index concurrently, on MySQL this
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# creates a regular index.
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#
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# Example:
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#
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# add_concurrent_index :users, :some_column
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#
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# See Rails' `add_index` for more info on the available arguments.
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def add_concurrent_index(*args)
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if transaction_open?
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raise 'add_concurrent_index can not be run inside a transaction, ' \
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'you can disable transactions by calling disable_ddl_transaction! ' \
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'in the body of your migration class'
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end
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if Database.postgresql?
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args << { algorithm: :concurrently }
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end
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add_index(*args)
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end
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# Updates the value of a column in batches.
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#
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# This method updates the table in batches of 5% of the total row count.
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# Any data inserted while running this method (or after it has finished
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# running) is _not_ updated automatically.
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#
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# This method _only_ updates rows where the column's value is set to NULL.
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#
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# table - The name of the table.
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# column - The name of the column to update.
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# value - The value for the column.
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def update_column_in_batches(table, column, value)
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quoted_table = quote_table_name(table)
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quoted_column = quote_column_name(column)
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##
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# Workaround for #17711
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#
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# It looks like for MySQL `ActiveRecord::Base.conntection.quote(true)`
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# returns correct value (1), but `ActiveRecord::Migration.new.quote`
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# returns incorrect value ('true'), which causes migrations to fail.
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#
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quoted_value = connection.quote(value)
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processed = 0
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total = exec_query("SELECT COUNT(*) AS count FROM #{quoted_table}").
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to_hash.
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first['count'].
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to_i
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# Update in batches of 5%
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batch_size = ((total / 100.0) * 5.0).ceil
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while processed < total
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start_row = exec_query(%Q{
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SELECT id
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FROM #{quoted_table}
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ORDER BY id ASC
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LIMIT 1 OFFSET #{processed}
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}).to_hash.first
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stop_row = exec_query(%Q{
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SELECT id
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FROM #{quoted_table}
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ORDER BY id ASC
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LIMIT 1 OFFSET #{processed + batch_size}
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}).to_hash.first
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query = %Q{
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UPDATE #{quoted_table}
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SET #{quoted_column} = #{quoted_value}
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WHERE id >= #{start_row['id']}
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}
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if stop_row
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query += " AND id < #{stop_row['id']}"
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end
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execute(query)
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processed += batch_size
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end
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end
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# Adds a column with a default value without locking an entire table.
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#
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# This method runs the following steps:
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#
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# 1. Add the column with a default value of NULL.
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# 2. Update all existing rows in batches.
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# 3. Change the default value of the column to the specified value.
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# 4. Update any remaining rows.
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#
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# These steps ensure a column can be added to a large and commonly used
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# table without locking the entire table for the duration of the table
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# modification.
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#
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# table - The name of the table to update.
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# column - The name of the column to add.
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# type - The column type (e.g. `:integer`).
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# default - The default value for the column.
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# allow_null - When set to `true` the column will allow NULL values, the
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# default is to not allow NULL values.
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def add_column_with_default(table, column, type, default:, allow_null: false)
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if transaction_open?
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raise 'add_column_with_default can not be run inside a transaction, ' \
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'you can disable transactions by calling disable_ddl_transaction! ' \
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'in the body of your migration class'
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end
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transaction do
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add_column(table, column, type, default: nil)
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# Changing the default before the update ensures any newly inserted
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# rows already use the proper default value.
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change_column_default(table, column, default)
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end
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begin
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transaction do
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update_column_in_batches(table, column, default)
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end
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# We want to rescue _all_ exceptions here, even those that don't inherit
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# from StandardError.
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rescue Exception => error # rubocop: disable all
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remove_column(table, column)
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raise error
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end
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change_column_null(table, column, false) unless allow_null
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end
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end
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end
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end
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