Class: ActiveRecord::Migration::ExecutionStrategy

Inherits:
Object
  • Object
show all
Defined in:
activerecord/lib/active_record/migration/execution_strategy.rb

Overview

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.

Direct Known Subclasses

DefaultStrategy

Instance Method Summary collapse

Constructor Details

#initialize(migration) ⇒ ExecutionStrategy

Returns a new instance of ExecutionStrategy.



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# File 'activerecord/lib/active_record/migration/execution_strategy.rb', line 43

def initialize(migration)
  @migration = migration
end