Rails ActiveRecord mysql2 adapter, use PreparedStatement by default

Question

PreparedStatement support for mysql2 has been already added in version 0.4.0, as per this link
As per following details in version 0.5.2 it still not uses prepared statement in all ORM queries internally:

Shipment.where(order_id: 78987898789)<br>
Shipment.where('order_id = ?', 56789876)

Mysql Log:

2019-03-10T13:20:01.722848Z  1072 Query SELECT `shipments`.* FROM `shipments` WHERE `shipments`.`order_id` = 78987898789<br>
2019-03-10T13:22:27.748687Z  1072 Query SELECT `shipments`.* FROM `shipments` WHERE (order_id = 56789876)

Is there a way to enable/disable it for all ORM queries? (Just like the PostgreSQL adapter ref). Does enabling it impact adversely on overall application performance?

If not, I haven't given a try yet but is it possible to achieve this using Sequel, and how complex is migrating an existing application from MySQL2 to Sequel.

Answer 1

ActiveRecord with Mysql2 < 5, doesn't support configurable parameter to enable prepared_statement
Code snippet from ActiveRecord 4.2.6

connection_adapters/mysql2_adapter.rb

module ConnectionAdapters
class Mysql2Adapter < AbstractMysqlAdapter
  ADAPTER_NAME = 'Mysql2'.freeze

  def initialize(connection, logger, connection_options, config)
    super
    @prepared_statements = false # No configurable param, default set to false
    configure_connection
  end
  ...
end

ActiveRecord with Mysql2 = 5.2.1 adapter support configurable parameter to enable prepared_statement Code snippet from ActiveRecord 5.2.1

connection_adapters/mysql2_adapter.rb

module ConnectionAdapters
class Mysql2Adapter < AbstractMysqlAdapter
  ADAPTER_NAME = "Mysql2".freeze

  include MySQL::DatabaseStatements

  def initialize(connection, logger, connection_options, config)
    super
    @prepared_statements = false unless config.key?(:prepared_statements)
    configure_connection
  end
  ...
end

So, in ActiveRecord 5.2.1, one can just add following line in database.yml to enable prepared_statements

prepared_statements: true