Class: ActiveRecord::ConnectionAdapters::AbstractAdapter

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

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 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, #case_sensitive_equality_operator, #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_column_options!, #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, #distinct, #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:



90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 90

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
  @query_cache         = Hash.new { |h,sql| h[sql] = {} }
  @query_cache_enabled = false
  @schema_cache        = SchemaCache.new self
  @visitor             = nil
  @prepared_statements = false
end

Instance Attribute Details

#in_use ⇒ Object (readonly) Also known as: in_use?

Returns the value of attribute in_use.



71
72
73
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 71

def in_use
  @in_use
end

#last_use ⇒ Object (readonly)

Returns the value of attribute last_use.



71
72
73
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 71

def last_use
  @last_use
end

#logger ⇒ Object (readonly)

Returns the value of attribute logger.



71
72
73
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 71

def logger
  @logger
end

#pool ⇒ Object

Returns the value of attribute pool.



70
71
72
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 70

def pool
  @pool
end

#schema_cache ⇒ Object

Returns the value of attribute schema_cache.



71
72
73
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 71

def schema_cache
  @schema_cache
end

#visitor ⇒ Object

Returns the value of attribute visitor.



70
71
72
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 70

def visitor
  @visitor
end

Class Method Details

.type_cast_config_to_boolean(config) ⇒ Object 



82
83
84
85
86
87
88
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 82

def self.type_cast_config_to_boolean(config)
  if config == "false"
    false
  else
    config
  end
end

.type_cast_config_to_integer(config) ⇒ Object 



74
75
76
77
78
79
80
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 74

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) 


326
327
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 326

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) 


331
332
333
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 331

def active_threadsafe?
  active?
end

#adapter_name ⇒ Object

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



211
212
213
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 211

def adapter_name
  'Abstract'
end

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



421
422
423
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 421

def case_insensitive_comparison(table, attribute, column, value)
  table[attribute].lower.eq(table.lower(value))
end

#case_sensitive_modifier(node) ⇒ Object 



417
418
419
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 417

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.



363
364
365
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 363

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

#close ⇒ Object

Check the connection back in to the connection pool



430
431
432
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 430

def close
  pool.checkin self
end

#create_savepoint ⇒ Object 



408
409
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 408

def create_savepoint
end

#current_savepoint_name ⇒ Object 



425
426
427
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 425

def current_savepoint_name
  "active_record_#{open_transactions}"
end

#decrement_open_transactions ⇒ Object 



398
399
400
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 398

def decrement_open_transactions
  ActiveSupport::Deprecation.warn "#decrement_open_transactions is deprecated and has no effect"
end

#disable_extension(name) ⇒ Object

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



287
288
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 287

def disable_extension(name)
end

#disable_referential_integrity ⇒ Object

Override to turn off referential integrity while executing &block.



317
318
319
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 317

def disable_referential_integrity
  yield
end

#disconnect! ⇒ Object

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



345
346
347
348
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 345

def disconnect!
  clear_cache!
  reset_transaction
end

#enable_extension(name) ⇒ Object

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



291
292
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 291

def enable_extension(name)
end

#expire ⇒ Object 



193
194
195
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 193

def expire
  @in_use = false
end

#extensions ⇒ Object

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



296
297
298
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 296

def extensions
  []
end

#increment_open_transactions ⇒ Object 



394
395
396
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 394

def increment_open_transactions
  ActiveSupport::Deprecation.warn "#increment_open_transactions is deprecated and has no effect"
end

#index_algorithms ⇒ Object

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



302
303
304
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 302

def index_algorithms
  {}
end

#lease ⇒ Object 



179
180
181
182
183
184
185
186
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 179

def lease
  synchronize do
    unless in_use
      @in_use   = true
      @last_use = Time.now
    end
  end
end

#open_transactions ⇒ Object 



390
391
392
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 390

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) 


255
256
257
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 255

def prefetch_primary_key?(table_name = nil)
  false
end

#raw_connection ⇒ Object

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.



386
387
388
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 386

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.



338
339
340
341
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 338

def reconnect!
  clear_cache!
  reset_transaction
end

#release_savepoint ⇒ Object 



414
415
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 414

def release_savepoint
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) 


369
370
371
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 369

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.



356
357
358
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 356

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

#rollback_to_savepoint ⇒ Object 



411
412
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 411

def rollback_to_savepoint
end

#schema_creation ⇒ Object 



175
176
177
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 175

def schema_creation
  SchemaCreation.new self
end

#substitute_at(column, index) ⇒ Object

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



310
311
312
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 310

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

#supports_bulk_alter? ⇒ Boolean

Returns:

  • (Boolean) 


241
242
243
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 241

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) 


230
231
232
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 230

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) 


237
238
239
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 237

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) 


271
272
273
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 271

def supports_explain?
  false
end

#supports_extensions? ⇒ Boolean

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

Returns:

  • (Boolean) 


282
283
284
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 282

def supports_extensions?
  false
end

#supports_index_sort_order? ⇒ Boolean

Does this adapter support index sort order?

Returns:

  • (Boolean) 


260
261
262
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 260

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) 


217
218
219
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 217

def supports_migrations?
  false
end

#supports_partial_index? ⇒ Boolean

Does this adapter support partial indices?

Returns:

  • (Boolean) 


265
266
267
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 265

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) 


224
225
226
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 224

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) 


247
248
249
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 247

def supports_savepoints?
  false
end

#supports_transaction_isolation? ⇒ Boolean

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

Returns:

  • (Boolean) 


276
277
278
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 276

def supports_transaction_isolation?
  false
end

#transaction_joinable=(joinable) ⇒ Object 



402
403
404
405
406
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 402

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 ⇒ Object 



201
202
203
204
205
206
207
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 201

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 ⇒ Object 



197
198
199
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 197

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

#valid_type?(type) ⇒ Boolean

Returns:

  • (Boolean) 


106
107
108
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 106

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.



376
377
378
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 376

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