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::Core#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 SchemaStatement are very useful.

Constants

SIMPLE_INT

Attributes

in_use[R]
in_use?[R]
last_use[R]
logger[R]
pool[RW]
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 81
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 73
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 325
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 210
def adapter_name
  'Abstract'
end
case_insensitive_comparison(table, attribute, column, value) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 414
def case_insensitive_comparison(table, attribute, column, value)
  table[attribute].lower.eq(table.lower(value))
end
case_sensitive_modifier(node) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 410
def case_sensitive_modifier(node)
  node
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 356
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 423
def close
  pool.checkin self
end
create_savepoint() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 401
def create_savepoint
end
current_savepoint_name() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 418
def current_savepoint_name
  "active_record_#{open_transactions}"
end
decrement_open_transactions() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 391
def decrement_open_transactions
  ActiveSupport::Deprecation.warn "#decrement_open_transactions is deprecated and has no effect"
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 286
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 316
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 338
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 290
def enable_extension(name)
end
expire() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 192
def expire
  @in_use = false
end
extensions() click to toggle source

A list of extensions, to be filled in by adapters that support them. At the moment only postgresql does.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 295
def extensions
  []
end
increment_open_transactions() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 387
def increment_open_transactions
  ActiveSupport::Deprecation.warn "#increment_open_transactions is deprecated and has no effect"
end
index_algorithms() click to toggle source

A list of index algorithms, to be filled by adapters that support them. MySQL and PostgreSQL have support for them right now.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 301
def index_algorithms
  {}
end
lease() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 178
def lease
  synchronize do
    unless in_use
      @in_use   = true
      @last_use = Time.now
    end
  end
end
open_transactions() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 383
def open_transactions
  @transaction.number
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. This is false for all adapters but Firebird.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 254
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 Mysql object in case of MysqlAdapter, 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 379
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 331
def reconnect!
  clear_cache!
  reset_transaction
end
release_savepoint() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 407
def release_savepoint
end
requires_reloading?() click to toggle source

Returns true if its required to reload the connection between requests for development mode. This is not the case for Ruby/MySQL and it's not necessary for any adapters except SQLite.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 362
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 349
def reset!
  # this should be overridden by concrete adapters
end
rollback_to_savepoint() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 404
def rollback_to_savepoint
end
schema_cache=(cache) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 187
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 174
def schema_creation
  SchemaCreation.new self
end
substitute_at(column, index) click to toggle source

Returns a bind substitution value given a column and list of current binds.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 309
def substitute_at(column, index)
  Arel::Nodes::BindParam.new '?'
end
supports_bulk_alter?() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 240
def supports_bulk_alter?
  false
end
supports_count_distinct?() click to toggle source

Does this adapter support using DISTINCT within COUNT? This is true for all adapters except sqlite.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 229
def supports_count_distinct?
  true
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? PostgreSQL, SQL Server, and others support this. MySQL and others do not.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 236
def supports_ddl_transactions?
  false
end
supports_explain?() click to toggle source

Does this adapter support explain? As of this writing sqlite3, mysql2, and postgresql are the only ones that do.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 270
def supports_explain?
  false
end
supports_extensions?() click to toggle source

Does this adapter support database extensions? As of this writing only postgresql does.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 281
def supports_extensions?
  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 259
def supports_index_sort_order?
  false
end
supports_migrations?() click to toggle source

Does this adapter support migrations? Backend specific, as the abstract adapter always returns false.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 216
def supports_migrations?
  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 264
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? Backend specific, as the abstract adapter always returns false.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 223
def supports_primary_key?
  false
end
supports_savepoints?() click to toggle source

Does this adapter support savepoints? PostgreSQL and MySQL do, SQLite < 3.6.8 does not.

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 246
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 275
def supports_transaction_isolation?
  false
end
transaction_joinable=(joinable) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 395
def transaction_joinable=(joinable)
  message = "#transaction_joinable= is deprecated. Please pass the :joinable option to #begin_transaction instead."
  ActiveSupport::Deprecation.warn message
  @transaction.joinable = joinable
end
unprepared_statement() { || ... } click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 200
def unprepared_statement
  old_prepared_statements, @prepared_statements = @prepared_statements, false
  old_visitor, @visitor = @visitor, unprepared_visitor
  yield
ensure
  @visitor, @prepared_statements = old_visitor, old_prepared_statements
end
unprepared_visitor() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 196
def unprepared_visitor
  self.class::BindSubstitution.new self
end
valid_type?(type) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 105
def valid_type?(type)
  true
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 369
def verify!(*ignored)
  reconnect! unless active?
end

Protected Instance Methods

log(sql, name = "SQL", binds = []) { || ... } click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 429
def log(sql, name = "SQL", binds = [])
  @instrumenter.instrument(
    "sql.active_record",
    :sql           => sql,
    :name          => name,
    :connection_id => object_id,
    :binds         => binds) { yield }
rescue => e
  message = "#{e.class.name}: #{e.message}: #{sql}"
  @logger.error message if @logger
  exception = translate_exception(e, message)
  exception.set_backtrace e.backtrace
  raise exception
end
translate_exception(exception, message) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 444
def translate_exception(exception, message)
  # override in derived class
  ActiveRecord::StatementInvalid.new(message, exception)
end
without_prepared_statement?(binds) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 449
def without_prepared_statement?(binds)
  !@prepared_statements || binds.empty?
end