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ActiveRecord::ConnectionAdapters::AbstractAdapter

Active Record supports multiple database systems. AbstractAdapter and related classes form the abstraction layer which makes this possible. An AbstractAdapter represents a connection to a database, and provides an abstract interface for database-specific functionality such as establishing a connection, escaping values, building the right SQL fragments for ‘:offset’ and ‘:limit’ options, etc.

All the concrete database adapters follow the interface laid down in this class. ActiveRecord::Base.connection returns an AbstractAdapter object, which you can use.

Most of the methods in the adapter are useful during migrations. Most notably, the instance methods provided by SchemaStatement are very useful.

Public Instance Methods

active?() click to toggle source

Checks whether the connection to the database is still active. This includes checking whether the database is actually capable of responding, i.e. whether the connection isn’t stale.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 117
def active?
  @active != false
end
adapter_name() click to toggle source

Returns the human-readable name of the adapter. Use mixed case - one can always use downcase if needed.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 49
def adapter_name
  'Abstract'
end
create_savepoint() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 183
def create_savepoint
end
current_savepoint_name() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 192
def current_savepoint_name
  "active_record_#{open_transactions}"
end
decrement_open_transactions() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 175
def decrement_open_transactions
  @open_transactions -= 1
end
disable_referential_integrity() click to toggle source

Override to turn off referential integrity while executing &block.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 108
def disable_referential_integrity
  yield
end
disconnect!() click to toggle source

Disconnects from the database if already connected. Otherwise, this method does nothing.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 129
def disconnect!
  @active = false
end
ids_in_list_limit() click to toggle source

Does this adapter restrict the number of ids you can use in a list. Oracle has a limit of 1000.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 94
def ids_in_list_limit
  nil
end
increment_open_transactions() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 170
def increment_open_transactions
  @open_transactions ||= 0
  @open_transactions += 1
end
open_transactions() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 166
def open_transactions
  @open_transactions ||= 0
end
prefetch_primary_key?(table_name = nil) click to toggle source

Should primary key values be selected from their corresponding sequence before the insert statement? If true, next_sequence_value is called before each insert to set the record’s primary key. This is false for all adapters but Firebird.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 89
def prefetch_primary_key?(table_name = nil)
  false
end
quote_table_name(name) click to toggle source

Override to return the quoted table name. Defaults to column quoting.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 101
def quote_table_name(name)
  quote_column_name(name)
end
raw_connection() click to toggle source

Provides access to the underlying database driver for this adapter. For example, this method returns a Mysql object in case of MysqlAdapter, and a PGconn object in case of PostgreSQLAdapter.

This is useful for when you need to call a proprietary method such as PostgreSQL’s lo_* methods.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 162
def raw_connection
  @connection
end
reconnect!() click to toggle source

Disconnects from the database if already connected, and establishes a new connection with the database.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 123
def reconnect!
  @active = true
end
release_savepoint() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 189
def release_savepoint
end
requires_reloading?() click to toggle source

Returns true if its required to reload the connection between requests for development mode. This is not the case for Ruby/MySQL and it’s not necessary for any adapters except SQLite.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 145
def requires_reloading?
  false
end
reset!() click to toggle source

Reset the state of this connection, directing the DBMS to clear transactions and other connection-related server-side state. Usually a database-dependent operation.

The default implementation does nothing; the implementation should be overridden by concrete adapters.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 139
def reset!
  # this should be overridden by concrete adapters
end
rollback_to_savepoint() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 186
def rollback_to_savepoint
end
supports_count_distinct?() click to toggle source

Does this adapter support using DISTINCT within COUNT? This is true for all adapters except sqlite.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 68
def supports_count_distinct?
  true
end
supports_ddl_transactions?() click to toggle source

Does this adapter support DDL rollbacks in transactions? That is, would CREATE TABLE or ALTER TABLE get rolled back by a transaction? PostgreSQL, SQL Server, and others support this. MySQL and others do not.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 75
def supports_ddl_transactions?
  false
end
supports_migrations?() click to toggle source

Does this adapter support migrations? Backend specific, as the abstract adapter always returns false.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 55
def supports_migrations?
  false
end
supports_primary_key?() click to toggle source

Can this adapter determine the primary key for tables not attached to an Active Record class, such as join tables? Backend specific, as the abstract adapter always returns false.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 62
def supports_primary_key?
  false
end
supports_savepoints?() click to toggle source

Does this adapter support savepoints? PostgreSQL and MySQL do, SQLite does not.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 81
def supports_savepoints?
  false
end
transaction_joinable=(joinable) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 179
def transaction_joinable=(joinable)
  @transaction_joinable = joinable
end
verify!(*ignored) click to toggle source

Checks whether the connection to the database is still active (i.e. not stale). This is done under the hood by calling active?. If the connection is no longer active, then this method will reconnect to the database.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 152
def verify!(*ignored)
  reconnect! unless active?
end

Protected Instance Methods

log(sql, name) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 198
def log(sql, name)
  name ||= "SQL"
  @instrumenter.instrument("sql.active_record",
    :sql => sql, :name => name, :connection_id => object_id) do
    yield
  end
rescue Exception => e
  message = "#{e.class.name}: #{e.message}: #{sql}"
  @logger.debug message if @logger
  raise translate_exception(e, message)
end
translate_exception(e, message) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 210
def translate_exception(e, message)
  # override in derived class
  ActiveRecord::StatementInvalid.new(message)
end

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