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 SchemaStatements are very useful.

Constants

ADAPTER_NAME
COMMENT_REGEX
SIMPLE_INT

Attributes

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

Public Class Methods

database_exists?(config) click to toggle source

Does the database for this adapter exist?

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 266
def self.database_exists?(config)
  raise NotImplementedError
end
type_cast_config_to_boolean(config) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 57
def self.type_cast_config_to_boolean(config)
  if config == "false"
    false
  else
    config
  end
end
type_cast_config_to_integer(config) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 47
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?() click to toggle source

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 469
def active?
end
adapter_name() click to toggle source

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 261
def adapter_name
  self.class::ADAPTER_NAME
end
clear_cache!() click to toggle source

Clear any caching the database adapter may be doing.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 520
def clear_cache!
  @lock.synchronize { @statements.clear } if @statements
end
close() click to toggle source

Check the connection back in to the connection pool

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 571
def close
  pool.checkin self
end
disable_extension(name) click to toggle source

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

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 422
def disable_extension(name)
end
disable_referential_integrity() { || ... } click to toggle source

Override to turn off referential integrity while executing &block.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 460
def disable_referential_integrity
  yield
end
discard!() click to toggle source

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.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 493
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
disconnect!() click to toggle source

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

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 482
def disconnect!
  clear_cache!
  reset_transaction
end
enable_extension(name) click to toggle source

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

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 426
def enable_extension(name)
end
expire() click to toggle source

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

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 218
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
extensions() click to toggle source

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

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 448
def extensions
  []
end
index_algorithms() click to toggle source

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

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 453
def index_algorithms
  {}
end
lease() click to toggle source

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

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 189
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
prefetch_primary_key?(table_name = nil) click to toggle source

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.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 293
def prefetch_primary_key?(table_name = nil)
  false
end
prepared_statements()
prepared_statements?() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 156
def prepared_statements?
  @prepared_statements && !prepared_statements_disabled_cache.include?(object_id)
end
Also aliased as: prepared_statements
preventing_writes?() click to toggle source

Determines whether writes are currently being prevented.

Returns true if the connection is a replica.

If the application is using legacy handling, returns true if connection_handler.prevent_writes is set.

If the application is using the new connection handling will return true based on current_preventing_writes.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 122
def preventing_writes?
  return true if replica?
  return ActiveRecord::Base.connection_handler.prevent_writes if ActiveRecord::Base.legacy_connection_handling
  return false if connection_klass.nil?

  connection_klass.current_preventing_writes
end
raw_connection() click to toggle source

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.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 542
def raw_connection
  disable_lazy_transactions!
  @connection
end
reconnect!() click to toggle source

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 475
def reconnect!
  clear_cache!
  reset_transaction
end
replica?() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 105
def replica?
  @config[:replica] || false
end
requires_reloading?() click to toggle source

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

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 525
def requires_reloading?
  false
end
reset!() click to toggle source

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 509
def reset!
  # this should be overridden by concrete adapters
end
schema_cache() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 208
def schema_cache
  @pool.get_schema_cache(self)
end
schema_cache=(cache) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 212
def schema_cache=(cache)
  cache.connection = self
  @pool.set_schema_cache(cache)
end
supports_advisory_locks?() click to toggle source

Does this adapter support application-enforced advisory locking?

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 286
def supports_advisory_locks?
  false
end
supports_bulk_alter?() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 276
def supports_bulk_alter?
  false
end
supports_check_constraints?() click to toggle source

Does this adapter support creating check constraints?

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 348
def supports_check_constraints?
  false
end
supports_comments?() click to toggle source

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

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 373
def supports_comments?
  false
end
supports_comments_in_create?() click to toggle source

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

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 378
def supports_comments_in_create?
  false
end
supports_common_table_expressions?() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 397
def supports_common_table_expressions?
  false
end
supports_datetime_with_precision?() click to toggle source

Does this adapter support datetime with precision?

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 363
def supports_datetime_with_precision?
  false
end
supports_ddl_transactions?() click to toggle source

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

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 272
def supports_ddl_transactions?
  false
end
supports_explain?() click to toggle source

Does this adapter support explain?

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 317
def supports_explain?
  false
end
supports_expression_index?() click to toggle source

Does this adapter support expression indices?

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 312
def supports_expression_index?
  false
end
supports_extensions?() click to toggle source

Does this adapter support database extensions?

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 327
def supports_extensions?
  false
end
supports_foreign_keys?() click to toggle source

Does this adapter support creating foreign key constraints?

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 338
def supports_foreign_keys?
  false
end
supports_foreign_tables?() click to toggle source

Does this adapter support foreign/external tables?

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 388
def supports_foreign_tables?
  false
end
supports_index_sort_order?() click to toggle source

Does this adapter support index sort order?

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 302
def supports_index_sort_order?
  false
end
supports_indexes_in_create?() click to toggle source

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

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 333
def supports_indexes_in_create?
  false
end
supports_insert_conflict_target?() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 417
def supports_insert_conflict_target?
  false
end
supports_insert_on_duplicate_skip?() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 409
def supports_insert_on_duplicate_skip?
  false
end
supports_insert_on_duplicate_update?() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 413
def supports_insert_on_duplicate_update?
  false
end
supports_insert_returning?() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 405
def supports_insert_returning?
  false
end
supports_json?() click to toggle source

Does this adapter support json data type?

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 368
def supports_json?
  false
end
supports_lazy_transactions?() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 401
def supports_lazy_transactions?
  false
end
supports_materialized_views?() click to toggle source

Does this adapter support materialized views?

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 358
def supports_materialized_views?
  false
end
supports_optimizer_hints?() click to toggle source

Does this adapter support optimizer hints?

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 393
def supports_optimizer_hints?
  false
end
supports_partial_index?() click to toggle source

Does this adapter support partial indices?

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 307
def supports_partial_index?
  false
end
supports_partitioned_indexes?() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 297
def supports_partitioned_indexes?
  false
end
supports_savepoints?() click to toggle source

Does this adapter support savepoints?

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 281
def supports_savepoints?
  false
end
supports_transaction_isolation?() click to toggle source

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

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 322
def supports_transaction_isolation?
  false
end
supports_validate_constraints?() click to toggle source

Does this adapter support creating invalid constraints?

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 343
def supports_validate_constraints?
  false
end
supports_views?() click to toggle source

Does this adapter support views?

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 353
def supports_views?
  false
end
supports_virtual_columns?() click to toggle source

Does this adapter support virtual columns?

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 383
def supports_virtual_columns?
  false
end
throw_away!() click to toggle source

Removes the connection from the pool and disconnect it.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 514
def throw_away!
  pool.remove self
  disconnect!
end
unprepared_statement() { || ... } click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 252
def unprepared_statement
  cache = prepared_statements_disabled_cache.add?(object_id) if @prepared_statements
  yield
ensure
  cache&.delete(object_id)
end
use_metadata_table?() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 109
def use_metadata_table?
  @config.fetch(:use_metadata_table, true)
end
verify!() click to toggle source

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 532
def verify!
  reconnect! unless active?
end

Private Instance Methods

arel_visitor() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 742
def arel_visitor
  Arel::Visitors::ToSql.new(self)
end
build_result(columns:, rows:, column_types: {}) click to toggle source

Builds the result object.

This is an internal hook to make possible connection adapters to build custom result objects with connection-specific data.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 753
def build_result(columns:, rows:, column_types: {})
  ActiveRecord::Result.new(columns, rows, column_types)
end
build_statement_pool() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 746
def build_statement_pool
end
can_perform_case_insensitive_comparison_for?(column) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 565
def can_perform_case_insensitive_comparison_for?(column)
  true
end
collector() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 728
def collector
  if prepared_statements
    Arel::Collectors::Composite.new(
      Arel::Collectors::SQLString.new,
      Arel::Collectors::Bind.new,
    )
  else
    Arel::Collectors::SubstituteBinds.new(
      self,
      Arel::Collectors::SQLString.new,
    )
  end
end
column_for(table_name, column_name) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 717
def column_for(table_name, column_name)
  column_name = column_name.to_s
  columns(table_name).detect { |c| c.name == column_name } ||
    raise(ActiveRecordError, "No such column: #{table_name}.#{column_name}")
end
column_for_attribute(attribute) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 723
def column_for_attribute(attribute)
  table_name = attribute.relation.name
  schema_cache.columns_hash(table_name)[attribute.name.to_s]
end
extract_limit(sql_type) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 672
def extract_limit(sql_type)
  $1.to_i if sql_type =~ /\((.*)\)/
end
extract_precision(sql_type) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 668
def extract_precision(sql_type)
  $1.to_i if sql_type =~ /\((\d+)(,\d+)?\)/
end
extract_scale(sql_type) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 661
def extract_scale(sql_type)
  case sql_type
  when /\((\d+)\)/ then 0
  when /\((\d+)(,(\d+))\)/ then $3.to_i
  end
end
initialize_type_map(m = type_map) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 609
def initialize_type_map(m = type_map)
  register_class_with_limit m, %r(boolean)i,       Type::Boolean
  register_class_with_limit m, %r(char)i,          Type::String
  register_class_with_limit m, %r(binary)i,        Type::Binary
  register_class_with_limit m, %r(text)i,          Type::Text
  register_class_with_precision m, %r(date)i,      Type::Date
  register_class_with_precision m, %r(time)i,      Type::Time
  register_class_with_precision m, %r(datetime)i,  Type::DateTime
  register_class_with_limit m, %r(float)i,         Type::Float
  register_class_with_limit m, %r(int)i,           Type::Integer

  m.alias_type %r(blob)i,      "binary"
  m.alias_type %r(clob)i,      "text"
  m.alias_type %r(timestamp)i, "datetime"
  m.alias_type %r(numeric)i,   "decimal"
  m.alias_type %r(number)i,    "decimal"
  m.alias_type %r(double)i,    "float"

  m.register_type %r(^json)i, Type::Json.new

  m.register_type(%r(decimal)i) do |sql_type|
    scale = extract_scale(sql_type)
    precision = extract_precision(sql_type)

    if scale == 0
      # FIXME: Remove this class as well
      Type::DecimalWithoutScale.new(precision: precision)
    else
      Type::Decimal.new(precision: precision, scale: scale)
    end
  end
end
log(sql, name = "SQL", binds = [], type_casted_binds = [], statement_name = nil) { || ... } click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 686
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:        self) do
    @lock.synchronize do
      yield
    end
  rescue => e
    raise translate_exception_class(e, sql, binds)
  end
end
register_class_with_limit(mapping, key, klass) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 647
def register_class_with_limit(mapping, key, klass)
  mapping.register_type(key) do |*args|
    limit = extract_limit(args.last)
    klass.new(limit: limit)
  end
end
register_class_with_precision(mapping, key, klass) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 654
def register_class_with_precision(mapping, key, klass)
  mapping.register_type(key) do |*args|
    precision = extract_precision(args.last)
    klass.new(precision: precision)
  end
end
reload_type_map() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 642
def reload_type_map
  type_map.clear
  initialize_type_map
end
translate_exception(exception, message:, sql:, binds:) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 703
def translate_exception(exception, message:, sql:, binds:)
  # override in derived class
  case exception
  when RuntimeError
    exception
  else
    ActiveRecord::StatementInvalid.new(message, sql: sql, binds: binds)
  end
end
translate_exception_class(e, sql, binds) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 676
def translate_exception_class(e, sql, binds)
  message = "#{e.class.name}: #{e.message}"

  exception = translate_exception(
    e, message: message, sql: sql, binds: binds
  )
  exception.set_backtrace e.backtrace
  exception
end
type_map() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 603
def type_map
  @type_map ||= Type::TypeMap.new.tap do |mapping|
    initialize_type_map(mapping)
  end
end
without_prepared_statement?(binds) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 713
def without_prepared_statement?(binds)
  !prepared_statements || binds.empty?
end