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
SIMPLE_INT

Attributes

in_use?[R]
logger[R]
owner[R]
pool[RW]
prepared_statements[R]
schema_cache[R]
visitor[RW]

Public Class Methods

type_cast_config_to_boolean(config) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 88
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 80
def self.type_cast_config_to_integer(config)
  if config =~ SIMPLE_INT
    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 356
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 199
def adapter_name
  self.class::ADAPTER_NAME
end
case_insensitive_comparison(table, attribute, column, value) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 421
def case_insensitive_comparison(table, attribute, column, value)
  if can_perform_case_insensitive_comparison_for?(column)
    table[attribute].lower.eq(table.lower(Arel::Nodes::BindParam.new))
  else
    table[attribute].eq(Arel::Nodes::BindParam.new)
  end
end
case_sensitive_comparison(table, attribute, column, value) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 413
def case_sensitive_comparison(table, attribute, column, value)
  if value.nil?
    table[attribute].eq(value)
  else
    table[attribute].eq(Arel::Nodes::BindParam.new)
  end
end
clear_cache!() click to toggle source

Clear any caching the database adapter may be doing, for example clearing the prepared statement cache. This is database specific.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 387
def clear_cache!
  # this should be overridden by concrete adapters
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 435
def close
  pool.checkin self
end
collector() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 144
def collector
  if prepared_statements
    SQLString.new
  else
    BindCollector.new
  end
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 313
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 347
def disable_referential_integrity
  yield
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 369
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 317
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 186
def expire
  @owner = nil
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 335
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 340
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 165
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 237
def prefetch_primary_key?(table_name = nil)
  false
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 PGconn object in case of PostgreSQLAdapter.

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

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 409
def raw_connection
  @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 362
def reconnect!
  clear_cache!
  reset_transaction
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 392
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 380
def reset!
  # this should be overridden by concrete adapters
end
schema_cache=(cache) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 180
def schema_cache=(cache)
  cache.connection = self
  @schema_cache = cache
end
schema_creation() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 160
def schema_creation
  SchemaCreation.new self
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 230
def supports_advisory_locks?
  false
end
supports_bulk_alter?() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 220
def supports_bulk_alter?
  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 298
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 303
def supports_comments_in_create?
  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 288
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 216
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 257
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 252
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 267
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 278
def supports_foreign_keys?
  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 242
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 273
def supports_indexes_in_create?
  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 293
def supports_json?
  false
end
supports_migrations?() click to toggle source

Does this adapter support migrations?

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 204
def supports_migrations?
  false
end
supports_multi_insert?() click to toggle source

Does this adapter support multi-value insert?

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 308
def supports_multi_insert?
  true
end
supports_partial_index?() click to toggle source

Does this adapter support partial indices?

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 247
def supports_partial_index?
  false
end
supports_primary_key?() click to toggle source

Can this adapter determine the primary key for tables not attached to an Active Record class, such as join tables?

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 210
def supports_primary_key?
  false
end
supports_savepoints?() click to toggle source

Does this adapter support savepoints?

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 225
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 262
def supports_transaction_isolation?
  false
end
supports_views?() click to toggle source

Does this adapter support views?

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 283
def supports_views?
  false
end
unprepared_statement() { || ... } click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 190
def unprepared_statement
  old_prepared_statements, @prepared_statements = @prepared_statements, false
  yield
ensure
  @prepared_statements = old_prepared_statements
end
valid_type?(type) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 156
def valid_type?(type)
  false
end
verify!(*ignored) 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 399
def verify!(*ignored)
  reconnect! unless active?
end

Protected Instance Methods

log(sql, name = "SQL", binds = [], statement_name = nil) { || ... } click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 559
def log(sql, name = "SQL", binds = [], statement_name = nil)
  @instrumenter.instrument(
    "sql.active_record",
    :sql            => sql,
    :name           => name,
    :connection_id  => object_id,
    :statement_name => statement_name,
    :binds          => binds) { yield }
rescue => e
  raise translate_exception_class(e, sql)
end
translate_exception(exception, message) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 571
def translate_exception(exception, message)
  # override in derived class
  ActiveRecord::StatementInvalid.new(message)
end
translate_exception_class(e, sql) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 547
def translate_exception_class(e, sql)
  begin
    message = "#{e.class.name}: #{e.message}: #{sql}"
  rescue Encoding::CompatibilityError
    message = "#{e.class.name}: #{e.message.force_encoding sql.encoding}: #{sql}"
  end

  exception = translate_exception(e, message)
  exception.set_backtrace e.backtrace
  exception
end
without_prepared_statement?(binds) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 576
def without_prepared_statement?(binds)
  !prepared_statements || binds.empty?
end

Private Instance Methods

can_perform_case_insensitive_comparison_for?(column) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 429
def can_perform_case_insensitive_comparison_for?(column)
  true
end