Module: Vitess::Activerecord::Migration

Defined in:
lib/vitess/activerecord/migration.rb,
lib/vitess/activerecord/migration/version.rb

Defined Under Namespace

Classes: Cancelled, Error, Failed, TimedOut

Constant Summary collapse

VERSION = 
"0.3.0"

Instance Method Summary collapse

Instance Method Details

#create_table(table_name, **options) ⇒ Object

Override the create_table method. If using the Vitess strategy, wait for the completion of the CREATE TABLE statement. This prevents an evaluation error from occurring if you try to execute a DDL on that table before the creation is complete.



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# File 'lib/vitess/activerecord/migration.rb', line 73

def create_table(table_name, **options)
  super(table_name, **options)

  # If create_table is called during revert, no additional processing is done.
  # We expect the DROP statement to be issued automatically during revert, but if execute is run here,
  # it will raise an IrreversibleMigration error, so this is to prevent that.
  return if down_migration_in_change_method?

  # If not using the Vitess strategy, do not wait for the completion of the CREATE TABLE statement.
  return unless vitess_strategy?

  wait_for_ddl
end

#default_ddl_strategy ⇒ Object

Returns the default DDL strategy. This method is called and set before executing the change, up, or down methods.

If you want to use a different strategy like direct, override this method.



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# File 'lib/vitess/activerecord/migration.rb', line 18

def default_ddl_strategy
  "vitess"
end

#exec_migration(connection, direction) ⇒ Object

Override exec_migration to set the default DDL strategy to vitess. This method is called every time a migration is executed. If you want to use a different DDL strategy, call with_ddl_strategy inside the change method or elsewhere.



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# File 'lib/vitess/activerecord/migration.rb', line 61

def exec_migration(connection, direction)
  @migration_direction = direction
  @using_change_method = self.respond_to?(:change)
  @migration_context = "#{self.version}_#{self.class.name.underscore}"
  with_ddl_strategy default_ddl_strategy do
    super(connection, direction)
  end
end

#migration_log_columns ⇒ Object

Returns the columns of SHOW VITESS_MIGRATIONS to log during the run.

Override this method if you want to change the default columns.



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# File 'lib/vitess/activerecord/migration.rb', line 44

def migration_log_columns
  %w[
    migration_uuid
    migration_statement
    added_timestamp
    started_timestamp
    last_throttled_timestamp
    last_cutover_attempt_timestamp
    is_immediate_operation
    progress
    eta_seconds
  ]
end

#raise_on_timeout ⇒ Object

Returns whether an error will be raised when the DDL statement exceeds wait_timeout_seconds.

Override this method if you want to change how timeouts are handled.



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# File 'lib/vitess/activerecord/migration.rb', line 37

def raise_on_timeout
  true
end

#wait_timeout_seconds ⇒ Object

Returns the timeout seconds for waiting for the completion of the DDL statement. If the DDL exceeds the timeout:

  • A warning will be logged.
  • An error will be raised and halt the Rails migration if raise_on_timeout is true.
  • The Vitess migration will continue.

Override this method if you want to change the default timeout.



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# File 'lib/vitess/activerecord/migration.rb', line 30

def wait_timeout_seconds
  7200 # 120 minutes
end

#with_ddl_strategy(strategy) ⇒ Object

Temporarily change the DDL strategy within the block.

You can use this method inside the change method to change the strategy only during the execution of specific DDL statements. However, note that this makes the migration irreversible, so if it’s possible to handle this by overriding the default_ddl_strategy, use that instead.



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# File 'lib/vitess/activerecord/migration.rb', line 91

def with_ddl_strategy(strategy)
  if enable_vitess?
    original_ddl_strategy = execute("SELECT @@ddl_strategy").first.first
    execute("SET @@ddl_strategy='#{strategy}'")
    execute("SET @@migration_context='#{@migration_context}'") unless strategy == "direct"
    begin
      yield
      wait_for_ddl unless strategy == "direct"
    ensure
      execute("SET @@ddl_strategy='#{original_ddl_strategy}'")
    end
  else
    yield
  end
end