Class: ActiveRecord::ConnectionAdapters::AbstractAdapter

Inherits:
Object
  • Object
show all
Includes:
ColumnDumper, DatabaseLimits, DatabaseStatements, QueryCache, Quoting, SchemaStatements, ActiveSupport::Callbacks, MonitorMixin
Defined in:
activerecord/lib/active_record/connection_adapters/abstract_adapter.rb,
activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb

Overview

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.

Defined Under Namespace

Classes: SchemaCreation

Constant Summary collapse

SIMPLE_INT =
/\A\d+\z/

Constants included from ActiveSupport::Callbacks

ActiveSupport::Callbacks::CALLBACK_FILTER_TYPES

Instance Attribute Summary collapse

Attributes included from QueryCache

#query_cache, #query_cache_enabled

Class Method Summary collapse

Instance Method Summary collapse

Methods included from ColumnDumper

#column_spec, #migration_keys, #prepare_column_options

Methods included from ActiveSupport::Callbacks

#run_callbacks

Methods included from ActiveSupport::Concern

#append_features, extended, #included

Methods included from QueryCache

#cache, #clear_query_cache, dirties_query_cache, #disable_query_cache!, #enable_query_cache!, included, #select_all, #uncached

Methods included from DatabaseLimits

#allowed_index_name_length, #column_name_length, #columns_per_multicolumn_index, #columns_per_table, #in_clause_length, #index_name_length, #indexes_per_table, #joins_per_query, #sql_query_length, #table_alias_length, #table_name_length

Methods included from Quoting

#quote, #quote_column_name, #quote_string, #quote_table_name, #quote_table_name_for_assignment, #quoted_date, #quoted_false, #quoted_true, #type_cast

Methods included from DatabaseStatements

#add_transaction_record, #begin_db_transaction, #begin_isolated_db_transaction, #begin_transaction, #commit_db_transaction, #commit_transaction, #current_transaction, #default_sequence_name, #delete, #empty_insert_statement_value, #exec_delete, #exec_insert, #exec_query, #exec_update, #execute, #insert, #insert_fixture, #join_to_delete, #join_to_update, #limited_update_conditions, #reset_sequence!, #reset_transaction, #rollback_db_transaction, #rollback_transaction, #sanitize_limit, #select_all, #select_one, #select_rows, #select_value, #select_values, #supports_statement_cache?, #to_sql, #transaction, #transaction_isolation_levels, #transaction_open?, #update, #within_new_transaction

Methods included from SchemaStatements

#add_column, #add_index, #add_reference, #add_timestamps, #assume_migrated_upto_version, #change_column, #change_column_default, #change_column_null, #change_table, #column_exists?, #columns, #columns_for_distinct, #create_join_table, #create_table, #drop_join_table, #drop_table, #dump_schema_information, #index_exists?, #index_name, #index_name_exists?, #initialize_schema_migrations_table, #native_database_types, #remove_column, #remove_columns, #remove_index, #remove_index!, #remove_reference, #remove_timestamps, #rename_column, #rename_index, #rename_table, #table_alias_for, #table_exists?, #type_to_sql, #update_table_definition

Constructor Details

#initialize(connection, logger = nil, pool = nil) ⇒ AbstractAdapter

:nodoc:


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 93

def initialize(connection, logger = nil, pool = nil) #:nodoc:
  super()

  @connection          = connection
  @in_use              = false
  @instrumenter        = ActiveSupport::Notifications.instrumenter
  @last_use            = false
  @logger              = logger
  @pool                = pool
  @schema_cache        = SchemaCache.new self
  @visitor             = nil
  @prepared_statements = false
end

Instance Attribute Details

#in_useObject (readonly) Also known as: in_use?

Returns the value of attribute in_use


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 74

def in_use
  @in_use
end

#last_useObject (readonly)

Returns the value of attribute last_use


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 74

def last_use
  @last_use
end

#loggerObject (readonly)

Returns the value of attribute logger


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 74

def logger
  @logger
end

#poolObject

Returns the value of attribute pool


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 73

def pool
  @pool
end

#schema_cacheObject

Returns the value of attribute schema_cache


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 74

def schema_cache
  @schema_cache
end

#visitorObject

Returns the value of attribute visitor


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 73

def visitor
  @visitor
end

Class Method Details

.type_cast_config_to_boolean(config) ⇒ Object


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# File 'activerecord/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) ⇒ Object


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# File 'activerecord/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

Instance Method Details

#active?Boolean

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.

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 262

def active?
end

#active_threadsafe?Boolean

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

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 267

def active_threadsafe?
  active?
end

#adapter_nameObject

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 147

def adapter_name
  'Abstract'
end

#case_insensitive_comparison(table, attribute, column, value) ⇒ Object


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# File 'activerecord/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) ⇒ Object


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 339

def case_sensitive_modifier(node)
  node
end

#clear_cache!Object

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 299

def clear_cache!
  # this should be overridden by concrete adapters
end

#closeObject

Check the connection back in to the connection pool


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 352

def close
  pool.checkin self
end

#create_savepoint(name = nil) ⇒ Object


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 330

def create_savepoint(name = nil)
end

#current_savepoint_nameObject


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 347

def current_savepoint_name
  "active_record_#{open_transactions}"
end

#disable_extension(name) ⇒ Object

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 223

def disable_extension(name)
end

#disable_referential_integrityObject

Override to turn off referential integrity while executing &block.


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 253

def disable_referential_integrity
  yield
end

#disconnect!Object

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 281

def disconnect!
  clear_cache!
  reset_transaction
end

#enable_extension(name) ⇒ Object

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 227

def enable_extension(name)
end

#expireObject


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 129

def expire
  @in_use = false
end

#extensionsObject

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 232

def extensions
  []
end

#index_algorithmsObject

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 238

def index_algorithms
  {}
end

#leaseObject


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# File 'activerecord/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_transactionsObject


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 326

def open_transactions
  @transaction.number
end

#prefetch_primary_key?(table_name = nil) ⇒ Boolean

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.

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 191

def prefetch_primary_key?(table_name = nil)
  false
end

#raw_connectionObject

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.


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 322

def raw_connection
  @connection
end

#reconnect!Object

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.


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 274

def reconnect!
  clear_cache!
  reset_transaction
end

#release_savepoint(name = nil) ⇒ Object


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 336

def release_savepoint(name = nil)
end

#requires_reloading?Boolean

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.

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 305

def requires_reloading?
  false
end

#reset!Object

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.


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# File 'activerecord/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) ⇒ Object


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 333

def rollback_to_savepoint(name = nil)
end

#schema_creationObject


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 111

def schema_creation
  SchemaCreation.new self
end

#substitute_at(column, index) ⇒ Object

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 246

def substitute_at(column, index)
  Arel::Nodes::BindParam.new '?'
end

#supports_bulk_alter?Boolean

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 177

def supports_bulk_alter?
  false
end

#supports_count_distinct?Boolean

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

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 166

def supports_count_distinct?
  true
end

#supports_ddl_transactions?Boolean

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.

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 173

def supports_ddl_transactions?
  false
end

#supports_explain?Boolean

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

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 207

def supports_explain?
  false
end

#supports_extensions?Boolean

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

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 218

def supports_extensions?
  false
end

#supports_index_sort_order?Boolean

Does this adapter support index sort order?

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 196

def supports_index_sort_order?
  false
end

#supports_migrations?Boolean

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

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 153

def supports_migrations?
  false
end

#supports_partial_index?Boolean

Does this adapter support partial indices?

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 201

def supports_partial_index?
  false
end

#supports_primary_key?Boolean

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.

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 160

def supports_primary_key?
  false
end

#supports_savepoints?Boolean

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

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 183

def supports_savepoints?
  false
end

#supports_transaction_isolation?Boolean

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

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 212

def supports_transaction_isolation?
  false
end

#unprepared_statementObject


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# File 'activerecord/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_visitorObject


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 133

def unprepared_visitor
  self.class::BindSubstitution.new self
end

#valid_type?(type) ⇒ Boolean

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 107

def valid_type?(type)
  true
end

#verify!(*ignored) ⇒ Object

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.


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 312

def verify!(*ignored)
  reconnect! unless active?
end