2016-05-09 12:14:32 +00:00
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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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2016-06-06 14:30:17 +00:00
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def add_concurrent_index(table_name, column_name, options = {})
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2016-05-09 12:14:32 +00:00
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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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2016-06-06 14:30:17 +00:00
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options = options.merge({ algorithm: :concurrently })
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2016-07-15 01:50:46 +00:00
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disable_statement_timeout
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2016-05-09 12:14:32 +00:00
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end
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2016-06-06 14:30:17 +00:00
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add_index(table_name, column_name, options)
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2016-05-09 12:14:32 +00:00
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end
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2016-07-15 01:39:08 +00:00
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# Long-running migrations may take more than the timeout allowed by
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# the database. Disable the session's statement timeout to ensure
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# migrations don't get killed prematurely. (PostgreSQL only)
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def disable_statement_timeout
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ActiveRecord::Base.connection.execute('SET statement_timeout TO 0') if Database.postgresql?
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end
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2016-05-09 12:14:32 +00:00
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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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2016-06-15 14:42:52 +00:00
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# This method will continue updating rows until no rows remain.
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#
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2016-06-16 10:50:11 +00:00
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# When given a block this method will yield two values to the block:
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2016-06-15 14:42:52 +00:00
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#
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# 1. An instance of `Arel::Table` for the table that is being updated.
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# 2. The query to run as an Arel object.
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#
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# By supplying a block one can add extra conditions to the queries being
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# executed. Note that the same block is used for _all_ queries.
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#
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# Example:
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#
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# update_column_in_batches(:projects, :foo, 10) do |table, query|
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# query.where(table[:some_column].eq('hello'))
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# end
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#
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# This would result in this method updating only rows where
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# `projects.some_column` equals "hello".
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2016-05-09 12:14:32 +00:00
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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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2016-06-16 10:50:11 +00:00
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#
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# Rubocop's Metrics/AbcSize metric is disabled for this method as Rubocop
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# determines this method to be too complex while there's no way to make it
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# less "complex" without introducing extra methods (which actually will
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# make things _more_ complex).
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#
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# rubocop: disable Metrics/AbcSize
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2016-05-09 12:14:32 +00:00
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def update_column_in_batches(table, column, value)
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2016-06-15 14:42:52 +00:00
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table = Arel::Table.new(table)
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2016-06-15 14:42:52 +00:00
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count_arel = table.project(Arel.star.count.as('count'))
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count_arel = yield table, count_arel if block_given?
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total = exec_query(count_arel.to_sql).to_hash.first['count'].to_i
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2016-05-09 12:14:32 +00:00
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2016-06-16 10:50:11 +00:00
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return if total == 0
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2016-06-13 09:38:57 +00:00
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# Update in batches of 5% until we run out of any rows to update.
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2016-05-09 12:14:32 +00:00
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batch_size = ((total / 100.0) * 5.0).ceil
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2016-06-16 10:50:11 +00:00
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start_arel = table.project(table[:id]).order(table[:id].asc).take(1)
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start_arel = yield table, start_arel if block_given?
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start_id = exec_query(start_arel.to_sql).to_hash.first['id'].to_i
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2016-06-13 09:38:57 +00:00
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2016-06-16 10:50:11 +00:00
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loop do
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2016-06-15 14:42:52 +00:00
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stop_arel = table.project(table[:id]).
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2016-06-16 10:50:11 +00:00
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where(table[:id].gteq(start_id)).
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order(table[:id].asc).
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take(1).
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2016-06-16 10:50:11 +00:00
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skip(batch_size)
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2016-06-15 14:42:52 +00:00
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stop_arel = yield table, stop_arel if block_given?
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stop_row = exec_query(stop_arel.to_sql).to_hash.first
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2016-05-09 12:14:32 +00:00
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2016-06-16 10:50:11 +00:00
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update_arel = Arel::UpdateManager.new(ActiveRecord::Base).
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table(table).
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2016-06-15 14:42:52 +00:00
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set([[table[column], value]]).
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2016-06-16 10:50:11 +00:00
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where(table[:id].gteq(start_id))
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2016-05-09 12:14:32 +00:00
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if stop_row
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2016-06-16 10:50:11 +00:00
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stop_id = stop_row['id'].to_i
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start_id = stop_id
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update_arel = update_arel.where(table[:id].lt(stop_id))
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2016-05-09 12:14:32 +00:00
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end
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2016-06-16 10:50:11 +00:00
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update_arel = yield table, update_arel if block_given?
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2016-06-15 14:42:52 +00:00
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execute(update_arel.to_sql)
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2016-05-09 12:14:32 +00:00
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2016-06-16 10:50:11 +00:00
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# There are no more rows left to update.
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break unless stop_row
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2016-05-09 12:14:32 +00:00
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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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2016-06-15 14:42:52 +00:00
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# 2. Change the default value of the column to the specified value.
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# 3. Update all existing rows in batches.
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# 4. Set a `NOT NULL` constraint on the column if desired (the default).
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2016-05-09 12:14:32 +00:00
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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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2016-09-13 22:15:14 +00:00
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# limit - Sets a column limit. For example, for :integer, the default is
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# 4-bytes. Set `limit: 8` to allow 8-byte integers.
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2016-05-09 12:14:32 +00:00
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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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2016-06-15 14:42:52 +00:00
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#
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# This method can also take a block which is passed directly to the
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# `update_column_in_batches` method.
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2016-09-13 22:15:14 +00:00
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def add_column_with_default(table, column, type, default:, limit: nil, allow_null: false, &block)
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2016-05-09 12:14:32 +00:00
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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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2016-07-15 01:50:46 +00:00
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disable_statement_timeout
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2016-05-09 12:14:32 +00:00
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transaction do
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2016-09-13 22:15:14 +00:00
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if limit
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add_column(table, column, type, default: nil, limit: limit)
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else
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add_column(table, column, type, default: nil)
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end
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2016-05-09 12:14:32 +00:00
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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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2016-06-15 15:04:07 +00:00
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update_column_in_batches(table, column, default, &block)
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2016-06-13 09:22:58 +00:00
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2016-06-15 15:04:07 +00:00
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change_column_null(table, column, false) unless allow_null
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2016-05-11 12:11:04 +00:00
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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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2016-05-09 12:14:32 +00:00
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remove_column(table, column)
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raise error
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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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