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 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 85
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 77
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 262
def active?
end
active_threadsafe?() click to toggle source

Adapter should redefine this if it needs a threadsafe way to approximate if the connection is active

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 267
def active_threadsafe?
  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 147
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 343
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 339
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 299
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 352
def close
  pool.checkin self
end
create_savepoint(name = nil) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 330
def create_savepoint(name = nil)
end
current_savepoint_name() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 347
def current_savepoint_name
  "active_record_#{open_transactions}"
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 223
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 253
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 281
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 227
def enable_extension(name)
end
expire() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 129
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 232
def extensions
  []
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 238
def index_algorithms
  {}
end
lease() click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 115
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 326
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 191
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 322
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 274
def reconnect!
  clear_cache!
  reset_transaction
end
release_savepoint(name = nil) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 336
def release_savepoint(name = nil)
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 305
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 292
def reset!
  # this should be overridden by concrete adapters
end
rollback_to_savepoint(name = nil) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 333
def rollback_to_savepoint(name = nil)
end
schema_cache=(cache) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 124
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 111
def schema_creation
  SchemaCreation.new self
end
substitute_at(column, index) click to toggle source

Returns a bind substitution value given a bind index and column NOTE: The column param is currently being used by the sqlserver-adapter

# File lib/active_record/connection_adapters/abstract_adapter.rb, line 246
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 177
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 166
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 173
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 207
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 218
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 196
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 153
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 201
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 160
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 183
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 212
def supports_transaction_isolation?
  false
end
unprepared_statement() { || ... } click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 137
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 133
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 107
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 312
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 366
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 378
def translate_exception(exception, message)
  # override in derived class
  ActiveRecord::StatementInvalid.new(message, exception)
end
translate_exception_class(e, sql) click to toggle source
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 358
def translate_exception_class(e, sql)
  message = "#{e.class.name}: #{e.message}: #{sql}"
  @logger.error message if @logger
  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 383
def without_prepared_statement?(binds)
  !@prepared_statements || binds.empty?
end