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

Constructor Details

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

:nodoc:



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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 89

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.



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

def in_use
  @in_use
end

#last_use ⇒ Object (readonly)

Returns the value of attribute last_use.



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

def last_use
  @last_use
end

#logger ⇒ Object (readonly)

Returns the value of attribute logger.



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

def logger
  @logger
end

#pool ⇒ Object

Returns the value of attribute pool.



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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 69

def pool
  @pool
end

#schema_cache ⇒ Object

Returns the value of attribute schema_cache.



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

def schema_cache
  @schema_cache
end

#visitor ⇒ Object

Returns the value of attribute visitor.



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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 69

def visitor
  @visitor
end

Class Method Details

.type_cast_config_to_boolean(config) ⇒ Object 



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# 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) ⇒ Object 



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# 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

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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 325

def active?
end

#adapter_name ⇒ Object

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



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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 210

def adapter_name
  'Abstract'
end

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



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# 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) ⇒ Object 



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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 410

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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 356

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

#close ⇒ Object

Check the connection back in to the connection pool



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

def close
  pool.checkin self
end

#create_savepoint ⇒ Object 



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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 401

def create_savepoint
end

#current_savepoint_name ⇒ Object 



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

def current_savepoint_name
  "active_record_#{open_transactions}"
end

#decrement_open_transactions ⇒ Object 



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# 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) ⇒ Object

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



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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 286

def disable_extension(name)
end

#disable_referential_integrity ⇒ Object

Override to turn off referential integrity while executing &block.



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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 316

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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 338

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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 290

def enable_extension(name)
end

#expire ⇒ Object 



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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 192

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.



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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 295

def extensions
  []
end

#increment_open_transactions ⇒ Object 



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# 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 ⇒ Object

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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 301

def index_algorithms
  {}
end

#lease ⇒ Object 



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# 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 ⇒ Object 



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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 383

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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 254

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.



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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 379

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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 331

def reconnect!
  clear_cache!
  reset_transaction
end

#release_savepoint ⇒ Object 



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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 407

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) 


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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 362

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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 349

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

#rollback_to_savepoint ⇒ Object 



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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 404

def rollback_to_savepoint
end

#schema_creation ⇒ Object 



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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 174

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.



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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 309

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

#supports_bulk_alter? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 240

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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 229

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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 236

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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 270

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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 281

def supports_extensions?
  false
end

#supports_index_sort_order? ⇒ Boolean

Does this adapter support index sort order?

Returns:

  • (Boolean) 


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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 259

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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 216

def supports_migrations?
  false
end

#supports_partial_index? ⇒ Boolean

Does this adapter support partial indices?

Returns:

  • (Boolean) 


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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 264

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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 223

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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 246

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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 275

def supports_transaction_isolation?
  false
end

#transaction_joinable=(joinable) ⇒ Object 



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# 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 ⇒ Object 



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# 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 ⇒ Object 



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

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

#valid_type?(type) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 105

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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 369

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