Class: ActiveRecord::ConnectionAdapters::AbstractAdapter

Relationships & Source Files
Namespace Children
Classes: `Version`
Extension / Inclusion / Inheritance Descendants
Subclasses: AbstractMysqlAdapter, Mysql2Adapter, PostgreSQLAdapter, SQLite3Adapter, TrilogyAdapter
Super Chains via Extension / Inclusion / Inheritance
Class Chain: self, `::ActiveSupport::DescendantsTracker`
Instance Chain: self, `Savepoints`, `::ActiveRecord::QueryCache`, `DatabaseLimits`, `Quoting`, `DatabaseStatements`, `SchemaStatements`, `::ActiveSupport::Callbacks`
Inherits:	Object
Defined in:	activerecord/lib/active_record/connection_adapters/abstract_adapter.rb

Overview

Active Record Abstract Adapter

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.lease_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.

Constant Summary

ADAPTER_NAME =
# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 31
```
"Abstract"
```
COMMENT_REGEX =
# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 41
```
%r{(?:--.*\n)|/\*(?:[^*]|\*[^/])*\*/}
```
EXTENDED_TYPE_MAPS =
# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 942
```
Concurrent::Map.new
```
SIMPLE_INT =
# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 40
```
/\A\d+\z/
```
TYPE_MAP =
# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 941
```
Type::TypeMap.new.tap { |m| initialize_type_map(m) }
```

`::ActiveSupport::Callbacks` - Included

CALLBACK_FILTER_TYPES

`DatabaseStatements` - Included

DEFAULT_INSERT_VALUE

`::ActiveSupport::Callbacks` - Attributes & Methods

.__callbacks rw
#__callbacks readonly

Class Method Summary

.database_exists?(config) ⇒ Boolean

Does the database for this adapter exist?
.dbconsole(config, options = {})

Opens a database console session.
.find_cmd_and_exec(commands, *args)
.type_cast_config_to_boolean(config)
.type_cast_config_to_integer(config)
.validate_default_timezone(config)

`::ActiveSupport::DescendantsTracker` - self

descendants, subclasses

Instance Attribute Summary

#active? ⇒ Boolean readonly

Checks whether the connection to the database is still active.
#connected? ⇒ Boolean readonly

Checks whether the connection to the database was established.
#database_exists? ⇒ Boolean readonly
#in_use? readonly

Alias for #owner.
#lock readonly
#logger readonly
#owner (also: #in_use?) readonly
#pool rw
#pool=(value) rw
#prepared_statements readonly

Alias for #prepared_statements?.
#preventing_writes? ⇒ Boolean readonly

Determines whether writes are currently being prevented.
#replica? ⇒ Boolean readonly
#requires_reloading? ⇒ Boolean readonly

Returns true if its required to reload the connection between requests for development mode.
#savepoint_errors_invalidate_transactions? ⇒ Boolean readonly

Do TransactionRollbackErrors on savepoints affect the parent transaction?
#supports_advisory_locks? ⇒ Boolean readonly

Does this adapter support application-enforced advisory locking?
#supports_bulk_alter? ⇒ Boolean readonly
#supports_check_constraints? ⇒ Boolean readonly

Does this adapter support creating check constraints?
#supports_comments? ⇒ Boolean readonly

Does this adapter support metadata comments on database objects (tables, columns, indexes)?
#supports_comments_in_create? ⇒ Boolean readonly

Can comments for tables, columns, and indexes be specified in create/alter table statements?
#supports_common_table_expressions? ⇒ Boolean readonly
#supports_concurrent_connections? ⇒ Boolean readonly
#supports_datetime_with_precision? ⇒ Boolean readonly

Does this adapter support datetime with precision?
#supports_ddl_transactions? ⇒ Boolean readonly

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

Does this adapter support creating deferrable constraints?
#supports_exclusion_constraints? ⇒ Boolean readonly

Does this adapter support creating exclusion constraints?
#supports_explain? ⇒ Boolean readonly

Does this adapter support explain?
#supports_expression_index? ⇒ Boolean readonly

Does this adapter support expression indices?
#supports_extensions? ⇒ Boolean readonly

Does this adapter support database extensions?
#supports_foreign_keys? ⇒ Boolean readonly

Does this adapter support creating foreign key constraints?
#supports_foreign_tables? ⇒ Boolean readonly

Does this adapter support foreign/external tables?
#supports_index_include? ⇒ Boolean readonly

Does this adapter support including non-key columns?
#supports_index_sort_order? ⇒ Boolean readonly

Does this adapter support index sort order?
#supports_indexes_in_create? ⇒ Boolean readonly

Does this adapter support creating indexes in the same statement as creating the table?
#supports_insert_conflict_target? ⇒ Boolean readonly
#supports_insert_on_duplicate_skip? ⇒ Boolean readonly
#supports_insert_on_duplicate_update? ⇒ Boolean readonly
#supports_insert_returning? ⇒ Boolean readonly
#supports_json? ⇒ Boolean readonly

Does this adapter support JSON data type?
#supports_lazy_transactions? ⇒ Boolean readonly
#supports_materialized_views? ⇒ Boolean readonly

Does this adapter support materialized views?
#supports_nulls_not_distinct? ⇒ Boolean readonly
#supports_optimizer_hints? ⇒ Boolean readonly

Does this adapter support optimizer hints?
#supports_partial_index? ⇒ Boolean readonly

Does this adapter support partial indices?
#supports_partitioned_indexes? ⇒ Boolean readonly
#supports_restart_db_transaction? ⇒ Boolean readonly
#supports_savepoints? ⇒ Boolean readonly

Does this adapter support savepoints?
#supports_transaction_isolation? ⇒ Boolean readonly

Does this adapter support setting the isolation level for a transaction?
#supports_unique_constraints? ⇒ Boolean readonly

Does this adapter support creating unique constraints?
#supports_validate_constraints? ⇒ Boolean readonly

Does this adapter support creating invalid constraints?
#supports_views? ⇒ Boolean readonly

Does this adapter support views?
#supports_virtual_columns? ⇒ Boolean readonly

Does this adapter support virtual columns?
#visitor readonly

`DatabaseStatements` - Included

#begin_transaction, #commit_transaction, #current_transaction, #dirty_current_transaction, #materialize_transactions, #open_transactions, #rollback_transaction, #transaction_open?, #within_new_transaction

`SchemaStatements` - Included

#use_foreign_keys?

Instance Method Summary

#adapter_name

Returns the human-readable name of the adapter.
#check_all_foreign_keys_valid!

Override to check all foreign key constraints in a database.
#clear_cache!(new_connection: false)

Clear any caching the database adapter may be doing.
#close

Check the connection back in to the connection pool.
#connect!
#connection_retries
#default_timezone
#disable_extension(name)

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

Override to turn off referential integrity while executing &block.
#discard!

Immediately forget this connection ever existed.
#disconnect!

Disconnects from the database if already connected.
#enable_extension(name)

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

this method must only be called while holding connection pool’s mutex.
#extensions

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

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

this method must only be called while holding connection pool’s mutex.
#prefetch_primary_key?(table_name = nil) ⇒ Boolean

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? ⇒ Boolean (also: #prepared_statements) readonly
#raw_connection

Provides access to the underlying database driver for this adapter.
#reconnect!(restore_transactions: false)

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

Reset the state of this connection, directing the DBMS to clear transactions and other connection-related server-side state.
#retry_deadline
#role

The role (e.g. :writing) for the current connection.
#schema_cache
#schema_version

Returns the version identifier of the schema currently available in the database.
#shard

The shard (e.g. :default) for the current connection.
#throw_away!

Removes the connection from the pool and disconnect it.
#unprepared_statement
#verify!

Checks whether the connection to the database is still active (i.e. not stale).
#log(sql, name = "SQL", binds = [], type_casted_binds = [], async: false, &block) private

`Savepoints` - Included

#create_savepoint, #current_savepoint_name, #exec_rollback_to_savepoint, #release_savepoint

`DatabaseLimits` - Included

#index_name_length	Returns the maximum length of an index name.
#table_alias_length	Returns the maximum length of a table alias.
#table_name_length	Returns the maximum length of a table name.

`Quoting` - Included

#quote	Quotes the column value to help prevent SQL injection attacks.
#quote_column_name	Quotes the column name.
#quote_string	Quotes a string, escaping any ‘ (single quote) and \ (backslash) characters.
#quote_table_name	Quotes the table name.
#quote_table_name_for_assignment	Override to return the quoted table name for assignment.
#quoted_date	Quote date/time values for use in SQL input.
#quoted_false, #quoted_true,
#type_cast	Cast a `value` to a type that the database understands.
#unquoted_false, #unquoted_true

`DatabaseStatements` - Included

#add_transaction_record	Register a record with the current transaction so that its after_commit and after_rollback callbacks can be called.
#begin_db_transaction	Begins the transaction (and turns off auto-committing).
#begin_isolated_db_transaction	Begins the transaction with the isolation level set.
#commit_db_transaction	Commits the transaction (and turns on auto-committing).
#create	Alias for DatabaseStatements#insert.
#default_sequence_name,
#delete	Executes the delete statement and returns the number of rows affected.
#disable_lazy_transactions!, #empty_insert_statement_value, #enable_lazy_transactions!,
#exec_delete	Executes delete `sql` statement in the context of this connection using `binds` as the bind substitutes.
#exec_insert	Executes insert `sql` statement in the context of this connection using `binds` as the bind substitutes.
#exec_query	Executes `sql` statement in the context of this connection using `binds` as the bind substitutes.
#exec_update	Executes update `sql` statement in the context of this connection using `binds` as the bind substitutes.
#execute	Executes the SQL statement in the context of this connection and returns the raw result from the connection adapter.
#high_precision_current_timestamp	Returns an `::Arel` SQL literal for the CURRENT_TIMESTAMP for usage with arbitrary precision date/time columns.
#initialize,
#insert	Executes an INSERT query and returns the new record’s ID.
#insert_fixture	Inserts the given fixture into the table.
#insert_fixtures_set,
#reset_isolation_level	Hook point called after an isolated DB transaction is committed or rolled back.
#reset_sequence!	Set the sequence to the max value of the table’s column.
#restart_db_transaction,
#rollback_db_transaction	Rolls back the transaction (and turns on auto-committing).
#rollback_to_savepoint,
#sanitize_limit	Sanitizes the given LIMIT parameter in order to prevent SQL injection.
#select_all	Returns an `::ActiveRecord::Result` instance.
#select_one	Returns a record hash with the column names as keys and column values as values.
#select_rows	Returns an array of arrays containing the field values.
#select_value	Returns a single value from a record.
#select_values	Returns an array of the values of the first column in a select:
#to_sql	Converts an arel AST to SQL.
#transaction	Runs the given block in a database transaction, and returns the result of the block.
#transaction_isolation_levels,
#truncate	Executes the truncate statement.
#update	Executes the update statement and returns the number of rows affected.
#write_query?	Determines whether the SQL statement is a write query.

`SchemaStatements` - Included

#add_belongs_to	Alias for SchemaStatements#add_reference.
#add_check_constraint	Adds a new check constraint to the table.
#add_column	Add a new `type` column named `column_name` to `table_name`.
#add_foreign_key	Adds a new foreign key.
#add_index	Adds a new index to the table.
#add_reference	Adds a reference.
#add_timestamps	Adds timestamps (`created_at` and `updated_at`) columns to `table_name`.
#assume_migrated_upto_version,
#build_create_table_definition	Returns a `TableDefinition` object containing information about the table that would be created if the same arguments were passed to `#create_table`.
#change_column	Changes the column’s definition according to the new options.
#change_column_comment	Changes the comment for a column or removes it if `nil`.
#change_column_default	Sets a new default value for a column:
#change_column_null	Sets or removes a `NOT NULL` constraint on a column.
#change_table	A block for changing columns in `table`.
#change_table_comment	Changes the comment for a table or removes it if `nil`.
#check_constraint_exists?	Checks to see if a check constraint exists on a table for a given check constraint definition.
#check_constraints	Returns an array of check constraints for the given table.
#column_exists?	Checks to see if a column exists in a given table.
#columns	Returns an array of `Column` objects for the table specified by `table_name`.
#create_join_table	Creates a new join table with the name created using the lexical order of the first two arguments.
#create_table	Creates a new table with the name `table_name`.
#data_source_exists?	Checks to see if the data source `name` exists on the database.
#data_sources	Returns the relation names usable to back Active Record models.
#drop_join_table	Drops the join table specified by the given arguments.
#drop_table	Drops a table or tables from the database.
#foreign_key_exists?	Checks to see if a foreign key exists on a table for a given foreign key definition.
#foreign_keys	Returns an array of foreign keys for the given table.
#index_exists?	Checks to see if an index exists on a table for a given index definition.
#index_name_exists?	Verifies the existence of an index with a given name.
#indexes	Returns an array of indexes for the given table.
#max_index_name_size	Returns the maximum length of an index name in bytes.
#native_database_types	Returns a hash of mappings from the abstract data types to the native database types.
#options_include_default?,
#primary_key	Returns just a table’s primary key.
#remove_belongs_to	Alias for SchemaStatements#remove_reference.
#remove_check_constraint	Removes the given check constraint from the table.
#remove_column	Removes the column from the table definition.
#remove_columns	Removes the given columns from the table definition.
#remove_foreign_key	Removes the given foreign key from the table.
#remove_index	Removes the given index from the table.
#remove_reference	Removes the reference(s).
#remove_timestamps	Removes the timestamp columns (`created_at` and `updated_at`) from the table definition.
#rename_column	Renames a column.
#rename_index	Renames an index.
#rename_table	Renames a table.
#table_alias_for	Truncates a table alias according to the limits of the current adapter.
#table_comment	Returns the table comment that’s stored in database metadata.
#table_exists?	Checks to see if the table `table_name` exists on the database.
#table_options,
#tables	Returns an array of table names defined in the database.
#view_exists?	Checks to see if the view `view_name` exists on the database.
#views	Returns an array of view names defined in the database.

`::ActiveSupport::Callbacks` - Included

#run_callbacks

Runs the callbacks for the given event.

Class Attribute Details

.__callbacks (rw)

[ GitHub ]

# File 'activesupport/lib/active_support/callbacks.rb', line 69


class_attribute :__callbacks, instance_writer: false, instance_predicate: false, default: {}

Class Method Details

.database_exists?(config) ⇒ `Boolean`

Does the database for this adapter exist?

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 360


def self.database_exists?(config)
  new(config).database_exists?
end

.dbconsole(config, options = {})

Opens a database console session.

Raises:

(NotImplementedError)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 121


def self.dbconsole(config, options = {})
  raise NotImplementedError
end

.find_cmd_and_exec(commands, *args)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 92


def self.find_cmd_and_exec(commands, *args) # :doc:
  commands = Array(commands)

  dirs_on_path = ENV["PATH"].to_s.split(File::PATH_SEPARATOR)
  unless (ext = RbConfig::CONFIG["EXEEXT"]).empty?
    commands = commands.map { |cmd| "#{cmd}#{ext}" }
  end

  full_path_command = nil
  found = commands.detect do |cmd|
    dirs_on_path.detect do |path|
      full_path_command = File.join(path, cmd)
      begin
        stat = File.stat(full_path_command)
      rescue SystemCallError
      else
        stat.file? && stat.executable?
      end
    end
  end

  if found
    exec full_path_command, *args
  else
    abort("Couldn't find database client: #{commands.join(', ')}. Check your $PATH and try again.")
  end
end

.type_cast_config_to_boolean(config)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 65


def self.type_cast_config_to_boolean(config)
  if config == "false"
    false
  else
    config
  end
end

.type_cast_config_to_integer(config)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 55


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

.validate_default_timezone(config)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 73


def self.validate_default_timezone(config)
  case config
  when nil
  when "utc", "local"
    config.to_sym
  else
    raise ArgumentError, "default_timezone must be either 'utc' or 'local'"
  end
end

Instance Attribute Details

#__callbacks (readonly)

[ GitHub ]

# File 'activesupport/lib/active_support/callbacks.rb', line 69


class_attribute :__callbacks, instance_writer: false, instance_predicate: false, default: {}

#active? ⇒ `Boolean` (readonly)

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.

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 658


def active?
end

#connected? ⇒ `Boolean` (readonly)

Checks whether the connection to the database was established. This doesn’t include checking whether the database is actually capable of responding, i.e. whether the connection is stale.

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 651


def connected?
  !@raw_connection.nil?
end

#database_exists? ⇒ `Boolean` (readonly)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 364


def database_exists?
  connect!
  true
rescue ActiveRecord::NoDatabaseError
  false
end

#in_use? (readonly)

Alias for #owner.

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 45


alias :in_use? :owner

#lock (readonly)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 44


attr_reader :visitor, :owner, :logger, :lock

#logger (readonly)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 44


attr_reader :visitor, :owner, :logger, :lock

#owner (readonly) Also known as: #in_use?

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 44


attr_reader :visitor, :owner, :logger, :lock

#pool (rw)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 43


attr_reader :pool

#pool=(value) (rw)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 47


def pool=(value)
  return if value.eql?(@pool)
  @schema_cache = nil
  @pool = value
end

#prepared_statements (readonly)

Alias for #prepared_statements?.

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 246


alias :prepared_statements :prepared_statements?

#preventing_writes? ⇒ `Boolean` (readonly)

Determines whether writes are currently being prevented.

Returns true if the connection is a replica or returns the value of current_preventing_writes.

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 236


def preventing_writes?
  return true if replica?
  return false if connection_class.nil?

  connection_class.current_preventing_writes
end

#replica? ⇒ `Boolean` (readonly)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 212


def replica?
  @config[:replica] || false
end

#requires_reloading? ⇒ `Boolean` (readonly)

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

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 752


def requires_reloading?
  false
end

#savepoint_errors_invalidate_transactions? ⇒ `Boolean` (readonly)

Do TransactionRollbackErrors on savepoints affect the parent transaction?

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 388


def savepoint_errors_invalidate_transactions?
  false
end

#supports_advisory_locks? ⇒ `Boolean` (readonly)

Does this adapter support application-enforced advisory locking?

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 397


def supports_advisory_locks?
  false
end

#supports_bulk_alter? ⇒ `Boolean` (readonly)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 377


def supports_bulk_alter?
  false
end

#supports_check_constraints? ⇒ `Boolean` (readonly)

Does this adapter support creating check constraints?

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 469


def supports_check_constraints?
  false
end

#supports_comments? ⇒ `Boolean` (readonly)

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

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 504


def supports_comments?
  false
end

#supports_comments_in_create? ⇒ `Boolean` (readonly)

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

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 509


def supports_comments_in_create?
  false
end

#supports_common_table_expressions? ⇒ `Boolean` (readonly)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 528


def supports_common_table_expressions?
  false
end

#supports_concurrent_connections? ⇒ `Boolean` (readonly)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 552


def supports_concurrent_connections?
  true
end

#supports_datetime_with_precision? ⇒ `Boolean` (readonly)

Does this adapter support datetime with precision?

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 494


def supports_datetime_with_precision?
  false
end

#supports_ddl_transactions? ⇒ `Boolean` (readonly)

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

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 373


def supports_ddl_transactions?
  false
end

#supports_deferrable_constraints? ⇒ `Boolean` (readonly)

Does this adapter support creating deferrable constraints?

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 464


def supports_deferrable_constraints?
  false
end

#supports_exclusion_constraints? ⇒ `Boolean` (readonly)

Does this adapter support creating exclusion constraints?

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 474


def supports_exclusion_constraints?
  false
end

#supports_explain? ⇒ `Boolean` (readonly)

Does this adapter support explain?

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 433


def supports_explain?
  false
end

#supports_expression_index? ⇒ `Boolean` (readonly)

Does this adapter support expression indices?

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 428


def supports_expression_index?
  false
end

#supports_extensions? ⇒ `Boolean` (readonly)

Does this adapter support database extensions?

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 443


def supports_extensions?
  false
end

#supports_foreign_keys? ⇒ `Boolean` (readonly)

Does this adapter support creating foreign key constraints?

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 454


def supports_foreign_keys?
  false
end

#supports_foreign_tables? ⇒ `Boolean` (readonly)

Does this adapter support foreign/external tables?

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 519


def supports_foreign_tables?
  false
end

#supports_index_include? ⇒ `Boolean` (readonly)

Does this adapter support including non-key columns?

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 423


def supports_index_include?
  false
end

#supports_index_sort_order? ⇒ `Boolean` (readonly)

Does this adapter support index sort order?

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 413


def supports_index_sort_order?
  false
end

#supports_indexes_in_create? ⇒ `Boolean` (readonly)

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

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 449


def supports_indexes_in_create?
  false
end

#supports_insert_conflict_target? ⇒ `Boolean` (readonly)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 548


def supports_insert_conflict_target?
  false
end

#supports_insert_on_duplicate_skip? ⇒ `Boolean` (readonly)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 540


def supports_insert_on_duplicate_skip?
  false
end

#supports_insert_on_duplicate_update? ⇒ `Boolean` (readonly)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 544


def supports_insert_on_duplicate_update?
  false
end

#supports_insert_returning? ⇒ `Boolean` (readonly)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 536


def supports_insert_returning?
  false
end

#supports_json? ⇒ `Boolean` (readonly)

Does this adapter support JSON data type?

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 499


def supports_json?
  false
end

#supports_lazy_transactions? ⇒ `Boolean` (readonly)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 532


def supports_lazy_transactions?
  false
end

#supports_materialized_views? ⇒ `Boolean` (readonly)

Does this adapter support materialized views?

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 489


def supports_materialized_views?
  false
end

#supports_nulls_not_distinct? ⇒ `Boolean` (readonly)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 556


def supports_nulls_not_distinct?
  false
end

#supports_optimizer_hints? ⇒ `Boolean` (readonly)

Does this adapter support optimizer hints?

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 524


def supports_optimizer_hints?
  false
end

#supports_partial_index? ⇒ `Boolean` (readonly)

Does this adapter support partial indices?

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 418


def supports_partial_index?
  false
end

#supports_partitioned_indexes? ⇒ `Boolean` (readonly)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 408


def supports_partitioned_indexes?
  false
end

#supports_restart_db_transaction? ⇒ `Boolean` (readonly)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 392


def supports_restart_db_transaction?
  false
end

#supports_savepoints? ⇒ `Boolean` (readonly)

Does this adapter support savepoints?

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 382


def supports_savepoints?
  false
end

#supports_transaction_isolation? ⇒ `Boolean` (readonly)

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

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 438


def supports_transaction_isolation?
  false
end

#supports_unique_constraints? ⇒ `Boolean` (readonly)

Does this adapter support creating unique constraints?

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 479


def supports_unique_constraints?
  false
end

#supports_validate_constraints? ⇒ `Boolean` (readonly)

Does this adapter support creating invalid constraints?

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 459


def supports_validate_constraints?
  false
end

#supports_views? ⇒ `Boolean` (readonly)

Does this adapter support views?

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 484


def supports_views?
  false
end

#supports_virtual_columns? ⇒ `Boolean` (readonly)

Does this adapter support virtual columns?

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 514


def supports_virtual_columns?
  false
end

#visitor (readonly)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 44


attr_reader :visitor, :owner, :logger, :lock

Instance Method Details

#adapter_name

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

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 355


def adapter_name
  self.class::ADAPTER_NAME
end

#check_all_foreign_keys_valid!

Override to check all foreign key constraints in a database. The adapter should raise a ::ActiveRecord::StatementInvalid if foreign key constraints are not met.

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 643


def check_all_foreign_keys_valid!
end

#clear_cache!(new_connection: false)

Clear any caching the database adapter may be doing.

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 739


def clear_cache!(new_connection: false)
  if @statements
    @lock.synchronize do
      if new_connection
        @statements.reset
      else
        @statements.clear
      end
    end
  end
end

#close

Check the connection back in to the connection pool

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 829


def close
  pool.checkin self
end

#connect!

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 777


def connect!
  verify!
  self
end

#connection_retries

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 216


def connection_retries
  (@config[:connection_retries] || 1).to_i
end

#default_timezone

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 228


def default_timezone
  @default_timezone || ActiveRecord.default_timezone
end

#disable_extension(name)

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

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 570


def disable_extension(name, **)
end

#disable_referential_integrity

Override to turn off referential integrity while executing &block.

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 636


def disable_referential_integrity
  yield
end

#discard!

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.

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 714


def discard!
  # This should be overridden by concrete adapters.
end

#disconnect!

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

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 700


def disconnect!
  @lock.synchronize do
    clear_cache!(new_connection: true)
    reset_transaction
    @raw_connection_dirty = false
  end
end

#enable_extension(name)

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

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 574


def enable_extension(name, **)
end

#expire

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

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 312


def expire
  if in_use?
    if @owner != ActiveSupport::IsolatedExecutionState.context
      raise ActiveRecordError, "Cannot expire connection, " \
        "it is owned by a different thread: #{@owner}. " \
        "Current thread: #{ActiveSupport::IsolatedExecutionState.context}."
    end

    @idle_since = Process.clock_gettime(Process::CLOCK_MONOTONIC)
    @owner = nil
  else
    raise ActiveRecordError, "Cannot expire connection, it is not currently leased."
  end
end

#extensions

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

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 624


def extensions
  []
end

#index_algorithms

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

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 629


def index_algorithms
  {}
end

#lease

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

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 276


def lease
  if in_use?
    msg = +"Cannot lease connection, "
    if @owner == ActiveSupport::IsolatedExecutionState.context
      msg << "it is already leased by the current thread."
    else
      msg << "it is already in use by a different thread: #{@owner}. " \
             "Current thread: #{ActiveSupport::IsolatedExecutionState.context}."
    end
    raise ActiveRecordError, msg
  end

  @owner = ActiveSupport::IsolatedExecutionState.context
end

#log(sql, name = "SQL", binds = [], type_casted_binds = [], async: false, &block) (private)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 1128


def log(sql, name = "SQL", binds = [], type_casted_binds = [], async: false, &block) # :doc:
  @instrumenter.instrument(
    "sql.active_record",
    sql:               sql,
    name:              name,
    binds:             binds,
    type_casted_binds: type_casted_binds,
    async:             async,
    connection:        self,
    transaction:       current_transaction.user_transaction.presence,
    row_count:         0,
    &block
  )
rescue ActiveRecord::StatementInvalid => ex
  raise ex.set_query(sql, binds)
end

#prefetch_primary_key?(table_name = nil) ⇒ `Boolean`

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.

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 404


def prefetch_primary_key?(table_name = nil)
  false
end

#prepared_statements? ⇒ `Boolean` (readonly) Also known as: #prepared_statements

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 243


def prepared_statements?
  @prepared_statements && !prepared_statements_disabled_cache.include?(object_id)
end

#raw_connection

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.

Active Record cannot track if the database is getting modified using this client. If that is the case, generally you’ll want to invalidate the query cache using ActiveRecord::Base.clear_query_cache.

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 797


def raw_connection
  with_raw_connection do |conn|
    disable_lazy_transactions!
    @raw_connection_dirty = true
    conn
  end
end

#reconnect!(restore_transactions: false)

Disconnects from the database if already connected, and establishes a new connection with the database. Implementors should define private #reconnect instead.

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 664


def reconnect!(restore_transactions: false)
  retries_available = connection_retries
  deadline = retry_deadline && Process.clock_gettime(Process::CLOCK_MONOTONIC) + retry_deadline

  @lock.synchronize do
    reconnect

    enable_lazy_transactions!
    @raw_connection_dirty = false
    @verified = true

    reset_transaction(restore: restore_transactions) do
      clear_cache!(new_connection: true)
      configure_connection
    end
  rescue => original_exception
    translated_exception = translate_exception_class(original_exception, nil, nil)
    retry_deadline_exceeded = deadline && deadline < Process.clock_gettime(Process::CLOCK_MONOTONIC)

    if !retry_deadline_exceeded && retries_available > 0
      retries_available -= 1

      if retryable_connection_error?(translated_exception)
        backoff(connection_retries - retries_available)
        retry
      end
    end

    @verified = false

    raise translated_exception
  end
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.

If a database driver or protocol does not support such a feature, implementors may alias this to #reconnect!. Otherwise, implementors should call super immediately after resetting the connection (and while still holding @lock).

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 726


def reset!
  clear_cache!(new_connection: true)
  reset_transaction
  configure_connection
end

#retry_deadline

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 220


def retry_deadline
  if @config[:retry_deadline]
    @config[:retry_deadline].to_f
  else
    nil
  end
end

#role

The role (e.g. :writing) for the current connection. In a non-multi role application, :writing is returned.

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 297


def role
  @pool.role
end

#schema_cache

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 307


def schema_cache
  @pool.schema_cache || (@schema_cache ||= BoundSchemaReflection.for_lone_connection(@pool.schema_reflection, self))
end

#schema_version

Returns the version identifier of the schema currently available in the database. This is generally equal to the number of the highest- numbered migration that has been executed, or 0 if no schema information is present / the database is empty.

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 864


def schema_version
  pool.migration_context.current_version
end

#shard

The shard (e.g. :default) for the current connection. In a non-sharded application, :default is returned.

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 303


def shard
  @pool.shard
end

#throw_away!

Removes the connection from the pool and disconnect it.

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 733


def throw_away!
  pool.remove self
  disconnect!
end

#unprepared_statement

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 346


def unprepared_statement
  cache = prepared_statements_disabled_cache.add?(object_id) if @prepared_statements
  yield
ensure
  cache&.delete(object_id)
end

#verify!

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.

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 759


def verify!
  unless active?
    @lock.synchronize do
      if @unconfigured_connection
        @raw_connection = @unconfigured_connection
        @unconfigured_connection = nil
        configure_connection
        @verified = true
        return
      end

      reconnect!(restore_transactions: true)
    end
  end

  @verified = true
end

Class: ActiveRecord::ConnectionAdapters::AbstractAdapter

Overview

Active Record Abstract Adapter

Constant Summary

::ActiveSupport::Callbacks - Included

DatabaseStatements - Included

::ActiveSupport::Callbacks - Attributes & Methods

Class Method Summary

::ActiveSupport::DescendantsTracker - self

Instance Attribute Summary

DatabaseStatements - Included

SchemaStatements - Included

Instance Method Summary

Savepoints - Included

DatabaseLimits - Included

Quoting - Included

DatabaseStatements - Included

SchemaStatements - Included

::ActiveSupport::Callbacks - Included

Class Attribute Details

.__callbacks (rw)

Class Method Details

.database_exists?(config) ⇒ Boolean

.dbconsole(config, options = {})

.find_cmd_and_exec(commands, *args)

.type_cast_config_to_boolean(config)

.type_cast_config_to_integer(config)

.validate_default_timezone(config)

Instance Attribute Details

#__callbacks (readonly)

#active? ⇒ Boolean (readonly)

#connected? ⇒ Boolean (readonly)

#database_exists? ⇒ Boolean (readonly)

#in_use? (readonly)

#lock (readonly)

#logger (readonly)

#owner (readonly) Also known as: #in_use?

#pool (rw)

#pool=(value) (rw)

#prepared_statements (readonly)

#preventing_writes? ⇒ Boolean (readonly)

#replica? ⇒ Boolean (readonly)

#requires_reloading? ⇒ Boolean (readonly)

#savepoint_errors_invalidate_transactions? ⇒ Boolean (readonly)

#supports_advisory_locks? ⇒ Boolean (readonly)

#supports_bulk_alter? ⇒ Boolean (readonly)

#supports_check_constraints? ⇒ Boolean (readonly)

#supports_comments? ⇒ Boolean (readonly)

#supports_comments_in_create? ⇒ Boolean (readonly)

#supports_common_table_expressions? ⇒ Boolean (readonly)

#supports_concurrent_connections? ⇒ Boolean (readonly)

#supports_datetime_with_precision? ⇒ Boolean (readonly)

#supports_ddl_transactions? ⇒ Boolean (readonly)

#supports_deferrable_constraints? ⇒ Boolean (readonly)

#supports_exclusion_constraints? ⇒ Boolean (readonly)

#supports_explain? ⇒ Boolean (readonly)

#supports_expression_index? ⇒ Boolean (readonly)

#supports_extensions? ⇒ Boolean (readonly)

#supports_foreign_keys? ⇒ Boolean (readonly)

#supports_foreign_tables? ⇒ Boolean (readonly)

#supports_index_include? ⇒ Boolean (readonly)

#supports_index_sort_order? ⇒ Boolean (readonly)

#supports_indexes_in_create? ⇒ Boolean (readonly)

#supports_insert_conflict_target? ⇒ Boolean (readonly)

#supports_insert_on_duplicate_skip? ⇒ Boolean (readonly)

#supports_insert_on_duplicate_update? ⇒ Boolean (readonly)

#supports_insert_returning? ⇒ Boolean (readonly)

#supports_json? ⇒ Boolean (readonly)

#supports_lazy_transactions? ⇒ Boolean (readonly)

#supports_materialized_views? ⇒ Boolean (readonly)

#supports_nulls_not_distinct? ⇒ Boolean (readonly)

#supports_optimizer_hints? ⇒ Boolean (readonly)

#supports_partial_index? ⇒ Boolean (readonly)

#supports_partitioned_indexes? ⇒ Boolean (readonly)

#supports_restart_db_transaction? ⇒ Boolean (readonly)

#supports_savepoints? ⇒ Boolean (readonly)

#supports_transaction_isolation? ⇒ Boolean (readonly)

#supports_unique_constraints? ⇒ Boolean (readonly)

#supports_validate_constraints? ⇒ Boolean (readonly)

#supports_views? ⇒ Boolean (readonly)

`::ActiveSupport::Callbacks` - Included

`DatabaseStatements` - Included

`::ActiveSupport::Callbacks` - Attributes & Methods

`::ActiveSupport::DescendantsTracker` - self

`DatabaseStatements` - Included

`SchemaStatements` - Included

`Savepoints` - Included

`DatabaseLimits` - Included

`Quoting` - Included

`DatabaseStatements` - Included

`SchemaStatements` - Included

`::ActiveSupport::Callbacks` - Included

.database_exists?(config) ⇒ `Boolean`

#active? ⇒ `Boolean` (readonly)

#connected? ⇒ `Boolean` (readonly)

#database_exists? ⇒ `Boolean` (readonly)

#preventing_writes? ⇒ `Boolean` (readonly)

#replica? ⇒ `Boolean` (readonly)

#requires_reloading? ⇒ `Boolean` (readonly)

#savepoint_errors_invalidate_transactions? ⇒ `Boolean` (readonly)

#supports_advisory_locks? ⇒ `Boolean` (readonly)

#supports_bulk_alter? ⇒ `Boolean` (readonly)

#supports_check_constraints? ⇒ `Boolean` (readonly)

#supports_comments? ⇒ `Boolean` (readonly)

#supports_comments_in_create? ⇒ `Boolean` (readonly)

#supports_common_table_expressions? ⇒ `Boolean` (readonly)

#supports_concurrent_connections? ⇒ `Boolean` (readonly)

#supports_datetime_with_precision? ⇒ `Boolean` (readonly)

#supports_ddl_transactions? ⇒ `Boolean` (readonly)

#supports_deferrable_constraints? ⇒ `Boolean` (readonly)

#supports_exclusion_constraints? ⇒ `Boolean` (readonly)

#supports_explain? ⇒ `Boolean` (readonly)

#supports_expression_index? ⇒ `Boolean` (readonly)

#supports_extensions? ⇒ `Boolean` (readonly)

#supports_foreign_keys? ⇒ `Boolean` (readonly)

#supports_foreign_tables? ⇒ `Boolean` (readonly)

#supports_index_include? ⇒ `Boolean` (readonly)

#supports_index_sort_order? ⇒ `Boolean` (readonly)

#supports_indexes_in_create? ⇒ `Boolean` (readonly)

#supports_insert_conflict_target? ⇒ `Boolean` (readonly)

#supports_insert_on_duplicate_skip? ⇒ `Boolean` (readonly)

#supports_insert_on_duplicate_update? ⇒ `Boolean` (readonly)

#supports_insert_returning? ⇒ `Boolean` (readonly)

#supports_json? ⇒ `Boolean` (readonly)

#supports_lazy_transactions? ⇒ `Boolean` (readonly)

#supports_materialized_views? ⇒ `Boolean` (readonly)

#supports_nulls_not_distinct? ⇒ `Boolean` (readonly)

#supports_optimizer_hints? ⇒ `Boolean` (readonly)

#supports_partial_index? ⇒ `Boolean` (readonly)

#supports_partitioned_indexes? ⇒ `Boolean` (readonly)

#supports_restart_db_transaction? ⇒ `Boolean` (readonly)

#supports_savepoints? ⇒ `Boolean` (readonly)

#supports_transaction_isolation? ⇒ `Boolean` (readonly)

#supports_unique_constraints? ⇒ `Boolean` (readonly)

#supports_validate_constraints? ⇒ `Boolean` (readonly)

#supports_views? ⇒ `Boolean` (readonly)

#supports_virtual_columns? ⇒ `Boolean` (readonly)

#prefetch_primary_key?(table_name = nil) ⇒ `Boolean`

#prepared_statements? ⇒ `Boolean` (readonly) Also known as: #prepared_statements