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.
Constants
- SIMPLE_INT
Attributes
Public Class Methods
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 85 def self.type_cast_config_to_boolean(config) if config == "false" false else config end end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 77 def self.type_cast_config_to_integer(config) if config =~ SIMPLE_INT config.to_i else config end end
Public Instance Methods
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 262 def active? end
Adapter should redefine this if it needs a threadsafe way to approximate if the connection is active
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 267 def active_threadsafe? active? 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 147 def adapter_name 'Abstract' end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 343 def case_insensitive_comparison(table, attribute, column, value) table[attribute].lower.eq(table.lower(value)) end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 339 def case_sensitive_modifier(node) node end
Clear any caching the database adapter may be doing, for example clearing the prepared statement cache. This is database specific.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 299 def clear_cache! # this should be overridden by concrete adapters end
Check the connection back in to the connection pool
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 352 def close pool.checkin self end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 330 def create_savepoint(name = nil) end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 347 def current_savepoint_name "active_record_#{open_transactions}" end
This is meant to be implemented by the adapters that support extensions
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 223 def disable_extension(name) end
Override to turn off referential integrity while executing
&block
.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 253 def disable_referential_integrity yield end
Disconnects from the database if already connected. Otherwise, this method does nothing.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 281 def disconnect! clear_cache! reset_transaction end
This is meant to be implemented by the adapters that support extensions
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 227 def enable_extension(name) end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 129 def expire @in_use = false end
A list of extensions, to be filled in by adapters that support them. At the moment only postgresql does.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 232 def extensions [] end
A list of index algorithms, to be filled by adapters that support them. MySQL and PostgreSQL have support for them right now.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 238 def index_algorithms {} end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 115 def lease synchronize do unless in_use @in_use = true @last_use = Time.now end end end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 326 def open_transactions @transaction.number 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 191 def prefetch_primary_key?(table_name = nil) false 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 322 def raw_connection @connection end
Disconnects from the database if already connected, and establishes a new connection with the database. Implementors should call super if they override the default implementation.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 274 def reconnect! clear_cache! reset_transaction end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 336 def release_savepoint(name = nil) 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 305 def requires_reloading? false 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 292 def reset! # this should be overridden by concrete adapters end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 333 def rollback_to_savepoint(name = nil) end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 124 def schema_cache=(cache) cache.connection = self @schema_cache = cache end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 111 def schema_creation SchemaCreation.new self end
Returns a bind substitution value given a bind index
and
column
NOTE: The column param is currently being used by the
sqlserver-adapter
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 246 def substitute_at(column, index) Arel::Nodes::BindParam.new '?' end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 177 def supports_bulk_alter? false 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 166 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 173 def supports_ddl_transactions? false end
Does this adapter support explain? As of this writing sqlite3, mysql2, and postgresql are the only ones that do.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 207 def supports_explain? false end
Does this adapter support database extensions? As of this writing only postgresql does.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 218 def supports_extensions? false end
Does this adapter support index sort order?
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 196 def supports_index_sort_order? 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 153 def supports_migrations? false end
Does this adapter support partial indices?
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 201 def supports_partial_index? false 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 160 def supports_primary_key? false end
Does this adapter support savepoints? PostgreSQL and MySQL do, SQLite < 3.6.8 does not.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 183 def supports_savepoints? false end
Does this adapter support setting the isolation level for a transaction?
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 212 def supports_transaction_isolation? false end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 137 def unprepared_statement old_prepared_statements, @prepared_statements = @prepared_statements, false old_visitor, @visitor = @visitor, unprepared_visitor yield ensure @visitor, @prepared_statements = old_visitor, old_prepared_statements end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 133 def unprepared_visitor self.class::BindSubstitution.new self end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 107 def valid_type?(type) true 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 312 def verify!(*ignored) reconnect! unless active? end
Protected Instance Methods
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 366 def log(sql, name = "SQL", binds = [], statement_name = nil) @instrumenter.instrument( "sql.active_record", :sql => sql, :name => name, :connection_id => object_id, :statement_name => statement_name, :binds => binds) { yield } rescue => e raise translate_exception_class(e, sql) end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 378 def translate_exception(exception, message) # override in derived class ActiveRecord::StatementInvalid.new(message, exception) end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 358 def translate_exception_class(e, sql) message = "#{e.class.name}: #{e.message}: #{sql}" @logger.error message if @logger exception = translate_exception(e, message) exception.set_backtrace e.backtrace exception end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 383 def without_prepared_statement?(binds) !@prepared_statements || binds.empty? end