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class ActiveRecord::ConnectionAdapters::AbstractAdapter

Parent:
Object
Included modules:
ActiveSupport::Callbacks, ActiveRecord::ConnectionAdapters::Quoting, ActiveRecord::ConnectionAdapters::DatabaseStatements, ActiveRecord::ConnectionAdapters::SchemaStatements, ActiveRecord::ConnectionAdapters::DatabaseLimits, ActiveRecord::ConnectionAdapters::QueryCache, ActiveRecord::ConnectionAdapters::Savepoints

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 SchemaStatements are very useful.

Constants

ADAPTER_NAME
SIMPLE_INT

Attributes

in_use?[R]
lock[R]
logger[R]
owner[R]
pool[RW]
visitor[R]

Public Class Methods

database_exists?(config) Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 277
def self.database_exists?(config)
  raise NotImplementedError
end

Does the database for this adapter exist?

type_cast_config_to_boolean(config) Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 97
def self.type_cast_config_to_boolean(config)
  if config == "false"
    false
  else
    config
  end
end
type_cast_config_to_integer(config) Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 87
def self.type_cast_config_to_integer(config)
  if config.is_a?(Integer)
    config
  elsif SIMPLE_INT.match?(config)
    config.to_i
  else
    config
  end
end

Public Instance Methods

active?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 480
def active?
end

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.

adapter_name() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 272
def adapter_name
  self.class::ADAPTER_NAME
end

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

clear_cache!() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 525
def clear_cache!
  @lock.synchronize { @statements.clear } if @statements
end

Clear any caching the database adapter may be doing.

close() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 576
def close
  pool.checkin self
end

Check the connection back in to the connection pool

disable_extension(name) Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 433
def disable_extension(name)
end

This is meant to be implemented by the adapters that support extensions

disable_referential_integrity() { || ... } Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 471
def disable_referential_integrity
  yield
end

Override to turn off referential integrity while executing &block.

discard!() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 504
def discard!
  # This should be overridden by concrete adapters.
  #
  # Prevent @connection's finalizer from touching the socket, or
  # otherwise communicating with its server, when it is collected.
  if schema_cache.connection == self
    schema_cache.connection = nil
  end
end

Immediately forget this connection ever existed. Unlike disconnect!, this will not communicate with the server.

After calling this method, the behavior of all other methods becomes undefined. This is called internally just before a forked process gets rid of a connection that belonged to its parent.

disconnect!() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 493
def disconnect!
  clear_cache!
  reset_transaction
end

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

enable_extension(name) Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 437
def enable_extension(name)
end

This is meant to be implemented by the adapters that support extensions

expire() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 232
def expire
  if in_use?
    if @owner != Thread.current
      raise ActiveRecordError, "Cannot expire connection, " \
        "it is owned by a different thread: #{@owner}. " \
        "Current thread: #{Thread.current}."
    end

    @idle_since = Concurrent.monotonic_time
    @owner = nil
  else
    raise ActiveRecordError, "Cannot expire connection, it is not currently leased."
  end
end

this method must only be called while holding connection pool's mutex

extensions() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 459
def extensions
  []
end

A list of extensions, to be filled in by adapters that support them.

index_algorithms() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 464
def index_algorithms
  {}
end

A list of index algorithms, to be filled by adapters that support them.

lease() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 207
def lease
  if in_use?
    msg = +"Cannot lease connection, "
    if @owner == Thread.current
      msg << "it is already leased by the current thread."
    else
      msg << "it is already in use by a different thread: #{@owner}. " \
             "Current thread: #{Thread.current}."
    end
    raise ActiveRecordError, msg
  end

  @owner = Thread.current
end

this method must only be called while holding connection pool's mutex

prefetch_primary_key?(table_name = nil) Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 304
def prefetch_primary_key?(table_name = nil)
  false
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.

prepared_statements() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 179
def prepared_statements
  @prepared_statement_status.value
end
preventing_writes?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 152
def preventing_writes?
  replica? || ActiveRecord::Base.connection_handler.prevent_writes
end

Determines whether writes are currently being prevents.

Returns true if the connection is a replica, or if prevent_writes is set to true.

raw_connection() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 547
def raw_connection
  disable_lazy_transactions!
  @connection
end

Provides access to the underlying database driver for this adapter. For example, this method returns a Mysql2::Client object in case of Mysql2Adapter, and a PG::Connection object in case of PostgreSQLAdapter.

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

reconnect!() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 486
def reconnect!
  clear_cache!
  reset_transaction
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.

replica?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 144
def replica?
  @config[:replica] || false
end
requires_reloading?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 530
def requires_reloading?
  false
end

Returns true if its required to reload the connection between requests for development mode.

reset!() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 520
def reset!
  # this should be overridden by concrete adapters
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.

schema_cache() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 222
def schema_cache
  @pool.get_schema_cache(self)
end
schema_cache=(cache) Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 226
def schema_cache=(cache)
  cache.connection = self
  @pool.set_schema_cache(cache)
end
supports_advisory_locks?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 297
def supports_advisory_locks?
  false
end

Does this adapter support application-enforced advisory locking?

supports_bulk_alter?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 287
def supports_bulk_alter?
  false
end
supports_comments?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 382
def supports_comments?
  false
end

Does this adapter support metadata comments on database objects (tables, columns, indexes)?

supports_comments_in_create?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 387
def supports_comments_in_create?
  false
end

Can comments for tables, columns, and indexes be specified in create/alter table statements?

supports_datetime_with_precision?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 372
def supports_datetime_with_precision?
  false
end

Does this adapter support datetime with precision?

supports_ddl_transactions?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 283
def supports_ddl_transactions?
  false
end

Does this adapter support DDL rollbacks in transactions? That is, would CREATE TABLE or ALTER TABLE get rolled back by a transaction?

supports_explain?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 324
def supports_explain?
  false
end

Does this adapter support explain?

supports_expression_index?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 319
def supports_expression_index?
  false
end

Does this adapter support expression indices?

supports_extensions?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 334
def supports_extensions?
  false
end

Does this adapter support database extensions?

supports_foreign_keys?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 345
def supports_foreign_keys?
  false
end

Does this adapter support creating foreign key constraints?

supports_foreign_keys_in_create?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 356
def supports_foreign_keys_in_create?
  supports_foreign_keys?
end

Does this adapter support creating foreign key constraints in the same statement as creating the table?

supports_foreign_tables?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 403
def supports_foreign_tables?
  false
end

Does this adapter support foreign/external tables?

supports_index_sort_order?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 309
def supports_index_sort_order?
  false
end

Does this adapter support index sort order?

supports_indexes_in_create?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 340
def supports_indexes_in_create?
  false
end

Does this adapter support creating indexes in the same statement as creating the table?

supports_insert_conflict_target?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 428
def supports_insert_conflict_target?
  false
end
supports_insert_on_duplicate_skip?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 420
def supports_insert_on_duplicate_skip?
  false
end
supports_insert_on_duplicate_update?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 424
def supports_insert_on_duplicate_update?
  false
end
supports_insert_returning?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 416
def supports_insert_returning?
  false
end
supports_json?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 377
def supports_json?
  false
end

Does this adapter support json data type?

supports_lazy_transactions?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 412
def supports_lazy_transactions?
  false
end
supports_materialized_views?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 367
def supports_materialized_views?
  false
end

Does this adapter support materialized views?

supports_multi_insert?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 392
def supports_multi_insert?
  true
end

Does this adapter support multi-value insert?

supports_optimizer_hints?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 408
def supports_optimizer_hints?
  false
end

Does this adapter support optimizer hints?

supports_partial_index?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 314
def supports_partial_index?
  false
end

Does this adapter support partial indices?

supports_savepoints?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 292
def supports_savepoints?
  false
end

Does this adapter support savepoints?

supports_transaction_isolation?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 329
def supports_transaction_isolation?
  false
end

Does this adapter support setting the isolation level for a transaction?

supports_validate_constraints?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 350
def supports_validate_constraints?
  false
end

Does this adapter support creating invalid constraints?

supports_views?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 362
def supports_views?
  false
end

Does this adapter support views?

supports_virtual_columns?() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 398
def supports_virtual_columns?
  false
end

Does this adapter support virtual columns?

unprepared_statement() { || ... } Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 266
def unprepared_statement
  @prepared_statement_status.bind(false) { yield }
end
verify!() Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 537
def verify!
  reconnect! unless active?
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.

Private Instance Methods

log(sql, name = "SQL", binds = [], type_casted_binds = [], statement_name = nil) { || ... } Show source 
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 696
def log(sql, name = "SQL", binds = [], type_casted_binds = [], statement_name = nil) # :doc:
  @instrumenter.instrument(
    "sql.active_record",
    sql:               sql,
    name:              name,
    binds:             binds,
    type_casted_binds: type_casted_binds,
    statement_name:    statement_name,
    connection_id:     object_id,
    connection:        self) do
    @lock.synchronize do
      yield
    end
  rescue => e
    raise translate_exception_class(e, sql, binds)
  end
end

© 2004–2019 David Heinemeier Hansson
Licensed under the MIT License.