Class: 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.

Methods

active?
adapter_name
create_savepoint
current_savepoint_name
decrement_open_transactions
disable_referential_integrity
disconnect!
increment_open_transactions
log
open_transactions
prefetch_primary_key?
quote_table_name
raw_connection
reconnect!
release_savepoint
requires_reloading?
reset!
rollback_to_savepoint
supports_count_distinct?
supports_ddl_transactions?
supports_migrations?
supports_primary_key?
supports_savepoints?
transaction_joinable=
translate_exception
verify!

Included Modules

Quoting
DatabaseStatements
SchemaStatements
DatabaseLimits
QueryCache
ActiveSupport::Callbacks

Public Instance methods

active?()

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.

[ show source ]

       # File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 112
112:       def active?
113:         @active != false
114:       end

adapter_name()

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

[ show source ]

      # File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 49
49:       def adapter_name
50:         'Abstract'
51:       end

create_savepoint()

[ show source ]

       # File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 178
178:       def create_savepoint
179:       end

current_savepoint_name()

[ show source ]

       # File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 187
187:       def current_savepoint_name
188:         "active_record_#{open_transactions}"
189:       end

decrement_open_transactions()

[ show source ]

       # File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 170
170:       def decrement_open_transactions
171:         @open_transactions -= 1
172:       end

disable_referential_integrity()

Override to turn off referential integrity while executing &block.

[ show source ]

       # File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 103
103:       def disable_referential_integrity
104:         yield
105:       end

disconnect!()

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

[ show source ]

       # File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 124
124:       def disconnect!
125:         @active = false
126:       end

increment_open_transactions()

[ show source ]

       # File activerecord/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

open_transactions()

[ show source ]

       # File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 161
161:       def open_transactions
162:         @open_transactions ||= 0
163:       end

prefetch_primary_key?(table_name = nil)

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.

[ show source ]

      # File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 89
89:       def prefetch_primary_key?(table_name = nil)
90:         false
91:       end

quote_table_name(name)

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

[ show source ]

      # File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 96
96:       def quote_table_name(name)
97:         quote_column_name(name)
98:       end

raw_connection()

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.

[ show source ]

       # File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 157
157:       def raw_connection
158:         @connection
159:       end

reconnect!()

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

[ show source ]

       # File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 118
118:       def reconnect!
119:         @active = true
120:       end

release_savepoint()

[ show source ]

       # File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 184
184:       def release_savepoint
185:       end

requires_reloading?()

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.

[ show source ]

       # File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 140
140:       def requires_reloading?
141:         false
142:       end

reset!()

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.

[ show source ]

       # File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 134
134:       def reset!
135:         # this should be overridden by concrete adapters
136:       end

rollback_to_savepoint()

[ show source ]

       # File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 181
181:       def rollback_to_savepoint
182:       end

supports_count_distinct?()

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

[ show source ]

      # File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 68
68:       def supports_count_distinct?
69:         true
70:       end

supports_ddl_transactions?()

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.

[ show source ]

      # File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 75
75:       def supports_ddl_transactions?
76:         false
77:       end

supports_migrations?()

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

[ show source ]

      # File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 55
55:       def supports_migrations?
56:         false
57:       end

supports_primary_key?()

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.

[ show source ]

      # File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 62
62:       def supports_primary_key?
63:         false
64:       end

supports_savepoints?()

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

[ show source ]

      # File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 81
81:       def supports_savepoints?
82:         false
83:       end

transaction_joinable=(joinable)

[ show source ]

       # File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 174
174:       def transaction_joinable=(joinable)
175:         @transaction_joinable = joinable
176:       end

verify!(*ignored)

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.

[ show source ]

       # File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 147
147:       def verify!(*ignored)
148:         reconnect! unless active?
149:       end

Protected Instance methods

log(sql, name)

[ show source ]

       # File activerecord/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

translate_exception(e, message)

[ show source ]

       # File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 205
205:         def translate_exception(e, message)
206:           # override in derived class
207:           ActiveRecord::StatementInvalid.new(message)
208:         end