Execution Strategy¶ ↑

ExecutionStrategy is the base class for migration execution strategies. A migration execution strategy handles method calls made by migrations that the migration class does not implement directly.

When a migration calls methods like create_table, add_column, or add_index, these calls are delegated to the execution strategy, which determines how they should be executed.

Customizing Migration Execution¶ ↑

You can create custom execution strategies by subclassing ExecutionStrategy (or more commonly, ActiveRecord::Migration::DefaultStrategy) and overriding methods to customize migration behavior. For example:

class MyCustomStrategy < ActiveRecord::Migration::DefaultStrategy
  def create_table(table_name, **options)
    # Custom logic before creating a table
    puts "Creating table: #{table_name}"
    super
  end

  def drop_table(table_name, **options)
    # Custom logic for dropping tables
    super
  end
end

# Apply globally
config.active_record.migration_strategy = MyCustomStrategy

# Or apply to a specific adapter
ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.migration_strategy = MyCustomStrategy

The strategy receives the current migration instance when initialized, accessible via the migration attribute.