Object
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.
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 112 112: def active? 113: @active != false 114: 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 49: def adapter_name 50: 'Abstract' 51: end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 178 178: def create_savepoint 179: end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 187 187: def current_savepoint_name 188: "active_record_#{open_transactions}" 189: end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 170 170: def decrement_open_transactions 171: @open_transactions -= 1 172: end
Override to turn off referential integrity while executing &block.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 103 103: def disable_referential_integrity 104: yield 105: end
Disconnects from the database if already connected. Otherwise, this method does nothing.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 124 124: def disconnect! 125: @active = false 126: end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 165 165: def increment_open_transactions 166: @open_transactions ||= 0 167: @open_transactions += 1 168: end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 161 161: def open_transactions 162: @open_transactions ||= 0 163: 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 89: def prefetch_primary_key?(table_name = nil) 90: false 91: end
Override to return the quoted table name. Defaults to column quoting.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 96 96: def quote_table_name(name) 97: quote_column_name(name) 98: 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 157 157: def raw_connection 158: @connection 159: 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 118 118: def reconnect! 119: @active = true 120: end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 184 184: def release_savepoint 185: end
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 140 140: def requires_reloading? 141: false 142: 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 134 134: def reset! 135: # this should be overridden by concrete adapters 136: end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 181 181: def rollback_to_savepoint 182: 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 68: def supports_count_distinct? 69: true 70: 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 75: def supports_ddl_transactions? 76: false 77: 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 55: def supports_migrations? 56: false 57: end
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 62: def supports_primary_key? 63: false 64: end
Does this adapter support savepoints? PostgreSQL and MySQL do, SQLite does not.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 81 81: def supports_savepoints? 82: false 83: end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 174 174: def transaction_joinable=(joinable) 175: @transaction_joinable = joinable 176: 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 147 147: def verify!(*ignored) 148: reconnect! unless active? 149: end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 193 193: def log(sql, name) 194: name ||= "SQL" 195: @instrumenter.instrument("sql.active_record", 196: :sql => sql, :name => name, :connection_id => object_id) do 197: yield 198: end 199: rescue Exception => e 200: message = "#{e.class.name}: #{e.message}: #{sql}" 201: @logger.debug message if @logger 202: raise translate_exception(e, message) 203: end
Disabled; run with --debug to generate this.
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