Object
ActiveRecord 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.
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
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
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 182 def create_savepoint end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 191 def current_savepoint_name "active_record_#{open_transactions}" end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 174 def decrement_open_transactions @open_transactions -= 1 end
Override to turn off referential integrity while executing &block.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 108 def disable_referential_integrity(&block) yield end
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
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 169 def increment_open_transactions @open_transactions ||= 0 @open_transactions += 1 end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 195 def log_info(sql, name, ms) if @logger && @logger.debug? name = '%s (%.1fms)' % [name || 'SQL', ms] @logger.debug(format_log_entry(name, sql.squeeze(' '))) end end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 165 def open_transactions @open_transactions ||= 0 end
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
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
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 161 def raw_connection @connection end
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
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 188 def release_savepoint end
Returns true if its safe to reload the connection between requests for development mode.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 144 def requires_reloading? true end
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
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 185 def rollback_to_savepoint end
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
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
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
Can this adapter determine the primary key for tables not attached to an ActiveRecord 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
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
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 178 def transaction_joinable=(joinable) @transaction_joinable = joinable end
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 151 def verify!(*ignored) reconnect! unless active? end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 230 def format_log_entry(message, dump = nil) if ActiveRecord::Base.colorize_logging if @@row_even @@row_even = false message_color, dump_color = "4;36;1", "0;1" else @@row_even = true message_color, dump_color = "4;35;1", "0" end log_entry = " \e[#{message_color}m#{message}\e[0m " log_entry << "\e[#{dump_color}m%#{String === dump ? 's' : 'p'}\e[0m" % dump if dump log_entry else "%s %s" % [message, dump] end end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 203 def log(sql, name) if block_given? result = nil ms = Benchmark.ms { result = yield } @runtime += ms log_info(sql, name, ms) result else log_info(sql, name, 0) nil end rescue SystemExit, SignalException, NoMemoryError => e # Don't re-wrap these exceptions. They are probably not being caused by invalid # sql, but rather some external stimulus beyond the responsibilty of this code. # Additionaly, wrapping these exceptions with StatementInvalid would lead to # meaningful loss of data, such as losing SystemExit#status. raise e rescue Exception => e # Log message and raise exception. # Set last_verification to 0, so that connection gets verified # upon reentering the request loop @last_verification = 0 message = "#{e.class.name}: #{e.message}: #{sql}" log_info(message, name, 0) raise ActiveRecord::StatementInvalid, message end
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