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class ActiveRecord::ConnectionAdapters::AbstractAdapter

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.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.

Inherits From

Constants

"Abstract"
%r{(?:--.*\n)|/\*(?:[^*]|\*[^/])*\*/}
Concurrent::Map.new
/\A\d+\z/
Type::TypeMap.new.tap { |m| initialize_type_map(m) }

Attributes

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

Public class methods

Does the database for this adapter exist?

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 358
def self.database_exists?(config)
  new(config).database_exists?
end

Opens a database console session.

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 126
def self.dbconsole(config, options = {})
  raise NotImplementedError
end
Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 97
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
Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 70
def self.type_cast_config_to_boolean(config)
  if config == "false"
    false
  else
    config
  end
end
Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 60
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
Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 78
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

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.

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 648
def active?
end

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

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 353
def adapter_name
  self.class::ADAPTER_NAME
end

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

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 633
def check_all_foreign_keys_valid!
end

Clear any caching the database adapter may be doing.

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 729
def clear_cache!(new_connection: false)
  if @statements
    @lock.synchronize do
      if new_connection
        @statements.reset
      else
        @statements.clear
      end
    end
  end
end

Check the connection back in to the connection pool

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 819
def close
  pool.checkin self
end
Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 767
def connect!
  verify!
  self
end

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.

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 641
def connected?
  !@raw_connection.nil?
end
Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 214
def connection_retries
  (@config[:connection_retries] || 1).to_i
end
Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 362
def database_exists?
  connect!
  true
rescue ActiveRecord::NoDatabaseError
  false
end
Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 226
def default_timezone
  @default_timezone || ActiveRecord.default_timezone
end

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

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 568
def disable_extension(name, **)
end

Override to turn off referential integrity while executing &block.

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 626
def disable_referential_integrity
  yield
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.

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 704
def discard!
  # This should be overridden by concrete adapters.
end

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

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 690
def disconnect!
  @lock.synchronize do
    clear_cache!(new_connection: true)
    reset_transaction
    @raw_connection_dirty = false
  end
end

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

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 572
def enable_extension(name, **)
end

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

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 310
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

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

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 614
def extensions
  []
end

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

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 619
def index_algorithms
  {}
end

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

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 274
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
Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 48
def pool=(value)
  return if value.eql?(@pool)
  @schema_cache = nil
  @pool = value

  if @pool && ActiveRecord.lazily_load_schema_cache
    @pool.schema_reflection.load!(@pool)
  end
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.

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 402
def prefetch_primary_key?(table_name = nil)
  false
end

Alias for: prepared_statements?.

Also aliased as: prepared_statements.

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 241
def prepared_statements?
  @prepared_statements && !prepared_statements_disabled_cache.include?(object_id)
end

Determines whether writes are currently being prevented.

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

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 234
def preventing_writes?
  return true if replica?
  return false if connection_class.nil?

  connection_class.current_preventing_writes
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.

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.

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 787
def raw_connection
  with_raw_connection do |conn|
    disable_lazy_transactions!
    @raw_connection_dirty = true
    conn
  end
end

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

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 654
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
Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 210
def replica?
  @config[:replica] || false
end

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

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 742
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.

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).

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 716
def reset!
  clear_cache!(new_connection: true)
  reset_transaction
  configure_connection
end
Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 218
def retry_deadline
  if @config[:retry_deadline]
    @config[:retry_deadline].to_f
  else
    nil
  end
end

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

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 295
def role
  @pool.role
end

Do TransactionRollbackErrors on savepoints affect the parent transaction?

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 386
def savepoint_errors_invalidate_transactions?
  false
end
Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 305
def schema_cache
  @pool.schema_cache || (@schema_cache ||= BoundSchemaReflection.for_lone_connection(@pool.schema_reflection, self))
end

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.

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 854
def schema_version
  pool.migration_context.current_version
end

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

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 301
def shard
  @pool.shard
end

Does this adapter support application-enforced advisory locking?

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 395
def supports_advisory_locks?
  false
end
Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 375
def supports_bulk_alter?
  false
end

Does this adapter support creating check constraints?

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 467
def supports_check_constraints?
  false
end

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

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 502
def supports_comments?
  false
end

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

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 507
def supports_comments_in_create?
  false
end
Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 526
def supports_common_table_expressions?
  false
end
Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 550
def supports_concurrent_connections?
  true
end

Does this adapter support datetime with precision?

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 492
def supports_datetime_with_precision?
  false
end

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

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 371
def supports_ddl_transactions?
  false
end

Does this adapter support creating deferrable constraints?

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 462
def supports_deferrable_constraints?
  false
end

Does this adapter support creating exclusion constraints?

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 472
def supports_exclusion_constraints?
  false
end

Does this adapter support explain?

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 431
def supports_explain?
  false
end

Does this adapter support expression indices?

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 426
def supports_expression_index?
  false
end

Does this adapter support database extensions?

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 441
def supports_extensions?
  false
end

Does this adapter support creating foreign key constraints?

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 452
def supports_foreign_keys?
  false
end

Does this adapter support foreign/external tables?

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 517
def supports_foreign_tables?
  false
end

Does this adapter support including non-key columns?

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 421
def supports_index_include?
  false
end

Does this adapter support index sort order?

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 411
def supports_index_sort_order?
  false
end

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

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 447
def supports_indexes_in_create?
  false
end
Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 546
def supports_insert_conflict_target?
  false
end
Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 538
def supports_insert_on_duplicate_skip?
  false
end
Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 542
def supports_insert_on_duplicate_update?
  false
end
Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 534
def supports_insert_returning?
  false
end

Does this adapter support JSON data type?

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 497
def supports_json?
  false
end
Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 530
def supports_lazy_transactions?
  false
end

Does this adapter support materialized views?

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 487
def supports_materialized_views?
  false
end
Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 554
def supports_nulls_not_distinct?
  false
end

Does this adapter support optimizer hints?

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 522
def supports_optimizer_hints?
  false
end

Does this adapter support partial indices?

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 416
def supports_partial_index?
  false
end
Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 406
def supports_partitioned_indexes?
  false
end
Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 390
def supports_restart_db_transaction?
  false
end

Does this adapter support savepoints?

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 380
def supports_savepoints?
  false
end

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

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 436
def supports_transaction_isolation?
  false
end

Does this adapter support creating unique constraints?

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 477
def supports_unique_constraints?
  false
end

Does this adapter support creating invalid constraints?

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 457
def supports_validate_constraints?
  false
end

Does this adapter support views?

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 482
def supports_views?
  false
end

Does this adapter support virtual columns?

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 512
def supports_virtual_columns?
  false
end

Removes the connection from the pool and disconnect it.

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 723
def throw_away!
  pool.remove self
  disconnect!
end
Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 344
def unprepared_statement
  cache = prepared_statements_disabled_cache.add?(object_id) if @prepared_statements
  yield
ensure
  cache&.delete(object_id)
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.

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 749
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

Private instance methods

Source code GitHub
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 1115
def log(sql, name = "SQL", binds = [], type_casted_binds = [], statement_name = nil, async: false, &block) # :doc:
  @instrumenter.instrument(
    "sql.active_record",
    sql:               sql,
    name:              name,
    binds:             binds,
    type_casted_binds: type_casted_binds,
    statement_name:    statement_name,
    async:             async,
    connection:        self,
    row_count:         0,
    &block
  )
rescue ActiveRecord::StatementInvalid => ex
  raise ex.set_query(sql, binds)
end

Namespace

Definition files