class ActiveRecord::ConnectionAdapters::AbstractAdapter

Parent:: Object
Included modules:: ActiveRecord::ConnectionAdapters::Quoting, ActiveRecord::ConnectionAdapters::DatabaseStatements, ActiveRecord::ConnectionAdapters::SchemaStatements, ActiveRecord::ConnectionAdapters::DatabaseLimits, ActiveRecord::ConnectionAdapters::QueryCache, ActiveSupport::Callbacks, ActiveRecord::ConnectionAdapters::ColumnDumper

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

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) Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 91
def self.type_cast_config_to_boolean(config)
  if config == "false"
    false
  else
    config
  end
end

type_cast_config_to_integer(config) Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 83
def self.type_cast_config_to_integer(config)
  if config =~ SIMPLE_INT
    config.to_i
  else
    config
  end
end

Public Instance Methods

active?() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 296
def active?
end

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.

adapter_name() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 180
def adapter_name
  self.class::ADAPTER_NAME
end

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

case_insensitive_comparison(table, attribute, column, value) Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 369
def case_insensitive_comparison(table, attribute, column, value)
  table[attribute].lower.eq(table.lower(value))
end

case_sensitive_comparison(table, attribute, column, value) Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 363
def case_sensitive_comparison(table, attribute, column, value)
  table_attr = table[attribute]
  value = case_sensitive_modifier(value, table_attr) unless value.nil?
  table_attr.eq(value)
end

case_sensitive_modifier(node, table_attribute) Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 359
def case_sensitive_modifier(node, table_attribute)
  node
end

clear_cache!() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 327
def clear_cache!
  # this should be overridden by concrete adapters
end

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

close() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 378
def close
  pool.checkin self
end

Check the connection back in to the connection pool

collector() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 138
def collector
  if prepared_statements
    SQLString.new
  else
    BindCollector.new
  end
end

create_savepoint(name = nil) Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 353
def create_savepoint(name = nil)
end

current_savepoint_name() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 373
def current_savepoint_name
  current_transaction.savepoint_name
end

disable_extension(name) Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 259
def disable_extension(name)
end

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

disable_referential_integrity() { || ... } Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 287
def disable_referential_integrity
  yield
end

Override to turn off referential integrity while executing &block.

disconnect!() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 309
def disconnect!
  clear_cache!
  reset_transaction
end

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

enable_extension(name) Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 263
def enable_extension(name)
end

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

expire() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 167
def expire
  @owner = nil
end

extensions() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 267
def extensions
  []
end

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

index_algorithms() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 272
def index_algorithms
  {}
end

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

lease() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 154
def lease
  synchronize do
    unless in_use?
      @owner = Thread.current
    end
  end
end

new_column(name, default, cast_type, sql_type = nil, null = true) Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 388
def new_column(name, default, cast_type, sql_type = nil, null = true)
  Column.new(name, default, cast_type, sql_type, null)
end

prefetch_primary_key?(table_name = nil) Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 213
def prefetch_primary_key?(table_name = nil)
  false
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.

raw_connection() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 349
def raw_connection
  @connection
end

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.

reconnect!() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 302
def reconnect!
  clear_cache!
  reset_transaction
end

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.

release_savepoint(name = nil) Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 356
def release_savepoint(name = nil)
end

requires_reloading?() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 332
def requires_reloading?
  false
end

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

reset!() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 320
def reset!
  # this should be overridden by concrete adapters
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.

The default implementation does nothing; the implementation should be overridden by concrete adapters.

schema_cache=(cache) Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 162
def schema_cache=(cache)
  cache.connection = self
  @schema_cache = cache
end

schema_creation() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 150
def schema_creation
  SchemaCreation.new self
end

substitute_at(column, _unused = 0) Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 280
def substitute_at(column, _unused = 0)
  Arel::Nodes::BindParam.new
end

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

supports_bulk_alter?() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 201
def supports_bulk_alter?
  false
end

supports_ddl_transactions?() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 197
def supports_ddl_transactions?
  false
end

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

supports_explain?() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 228
def supports_explain?
  false
end

Does this adapter support explain?

supports_extensions?() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 238
def supports_extensions?
  false
end

Does this adapter support database extensions?

supports_foreign_keys?() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 249
def supports_foreign_keys?
  false
end

Does this adapter support creating foreign key constraints?

supports_index_sort_order?() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 218
def supports_index_sort_order?
  false
end

Does this adapter support index sort order?

supports_indexes_in_create?() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 244
def supports_indexes_in_create?
  false
end

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

supports_migrations?() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 185
def supports_migrations?
  false
end

Does this adapter support migrations?

supports_partial_index?() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 223
def supports_partial_index?
  false
end

Does this adapter support partial indices?

supports_primary_key?() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 191
def supports_primary_key?
  false
end

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

supports_savepoints?() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 206
def supports_savepoints?
  false
end

Does this adapter support savepoints?

supports_transaction_isolation?() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 233
def supports_transaction_isolation?
  false
end

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

supports_views?() Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 254
def supports_views?
  false
end

Does this adapter support views?

unprepared_statement() { || ... } Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 171
def unprepared_statement
  old_prepared_statements, @prepared_statements = @prepared_statements, false
  yield
ensure
  @prepared_statements = old_prepared_statements
end

valid_type?(type) Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 146
def valid_type?(type)
  true
end

verify!(*ignored) Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 339
def verify!(*ignored)
  reconnect! unless active?
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.

Protected Instance Methods

log(sql, name = "SQL", binds = [], statement_name = nil) { || ... } Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 477
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) Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 489
def translate_exception(exception, message)
  # override in derived class
  ActiveRecord::StatementInvalid.new(message, exception)
end

translate_exception_class(e, sql) Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 465
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) Show source

# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 494
def without_prepared_statement?(binds)
  !prepared_statements || binds.empty?
end

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