Class: ActiveRecord::ConnectionAdapters::AbstractAdapter

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

Overview

ActiveRecord 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.

Direct Known Subclasses

MysqlAdapter, PostgreSQLAdapter, SQLiteAdapter

Constant Summary collapse

@@row_even = 
true

Instance Attribute Summary

Attributes included from QueryCache

#query_cache, #query_cache_enabled

Instance Method Summary collapse

Methods included from QueryCache

#cache, #clear_query_cache, #columns_with_query_cache, dirties_query_cache, included, #select_all_with_query_cache, #uncached

Methods included from Quoting

#quote, #quote_column_name, #quote_string, #quoted_date, #quoted_false, #quoted_string_prefix, #quoted_true

Methods included from DatabaseStatements

#add_limit!, #add_limit_offset!, #add_lock!, #begin_db_transaction, #case_sensitive_equality_operator, #commit_db_transaction, #default_sequence_name, #delete, #empty_insert_statement, #execute, #insert, #insert_fixture, #limited_update_conditions, #outside_transaction?, #reset_sequence!, #rollback_db_transaction, #select_all, #select_one, #select_rows, #select_value, #select_values, #transaction, #update

Methods included from SchemaStatements

#add_column, #add_column_options!, #add_index, #add_order_by_for_association_limiting!, #add_timestamps, #assume_migrated_upto_version, #change_column, #change_column_default, #change_table, #columns, #create_table, #distinct, #drop_table, #dump_schema_information, #index_name, #initialize_schema_migrations_table, #native_database_types, #remove_column, #remove_index, #remove_timestamps, #rename_column, #rename_table, #structure_dump, #table_alias_for, #table_alias_length, #table_exists?, #type_to_sql

Constructor Details

#initialize(connection, logger = nil) ⇒ AbstractAdapter

:nodoc:



38
39
40
41
42
43
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 38

def initialize(connection, logger = nil) #:nodoc:
  @connection, @logger = connection, logger
  @runtime = 0
  @last_verification = 0
  @query_cache_enabled = false
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) 


108
109
110
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 108

def active?
  @active != false
end

#adapter_name ⇒ Object

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



47
48
49
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 47

def adapter_name
  'Abstract'
end

#create_savepoint ⇒ Object 



173
174
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 173

def create_savepoint
end

#current_savepoint_name ⇒ Object 



182
183
184
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 182

def current_savepoint_name
  "active_record_#{open_transactions}"
end

#decrement_open_transactions ⇒ Object 



165
166
167
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 165

def decrement_open_transactions
  @open_transactions -= 1
end

#disable_referential_integrity(&block) ⇒ Object

Override to turn off referential integrity while executing &block.



99
100
101
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 99

def disable_referential_integrity(&block)
  yield
end

#disconnect! ⇒ Object

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



120
121
122
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 120

def disconnect!
  @active = false
end

#increment_open_transactions ⇒ Object 



160
161
162
163
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 160

def increment_open_transactions
  @open_transactions ||= 0
  @open_transactions += 1
end

#log_info(sql, name, ms) ⇒ Object 



186
187
188
189
190
191
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 186

def log_info(sql, name, ms)
  if @logger && @logger.debug?
    name = '%s (%.1fms)' % [name || 'SQL', ms]
    @logger.debug(format_log_entry(name, sql.squeeze(' ')))
  end
end

#open_transactions ⇒ Object 



156
157
158
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 156

def open_transactions
  @open_transactions ||= 0
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) 


80
81
82
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 80

def prefetch_primary_key?(table_name = nil)
  false
end

#quote_table_name(name) ⇒ Object

Override to return the quoted table name. Defaults to column quoting.



92
93
94
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 92

def quote_table_name(name)
  quote_column_name(name)
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.



152
153
154
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 152

def raw_connection
  @connection
end

#reconnect! ⇒ Object

Disconnects from the database if already connected, and establishes a new connection with the database.



114
115
116
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 114

def reconnect!
  @active = true
end

#release_savepoint ⇒ Object 



179
180
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 179

def release_savepoint
end

#requires_reloading? ⇒ Boolean

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

Returns:

  • (Boolean) 


135
136
137
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 135

def requires_reloading?
  true
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.



130
131
132
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 130

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

#reset_runtime ⇒ Object

:nodoc:



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

def reset_runtime #:nodoc:
  rt, @runtime = @runtime, 0
  rt
end

#rollback_to_savepoint ⇒ Object 



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

def rollback_to_savepoint
end

#supports_count_distinct? ⇒ Boolean

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

Returns:

  • (Boolean) 


59
60
61
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 59

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) 


66
67
68
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 66

def supports_ddl_transactions?
  false
end

#supports_migrations? ⇒ Boolean

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

Returns:

  • (Boolean) 


53
54
55
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 53

def supports_migrations?
  false
end

#supports_savepoints? ⇒ Boolean

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

Returns:

  • (Boolean) 


72
73
74
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 72

def supports_savepoints?
  false
end

#transaction_joinable=(joinable) ⇒ Object 



169
170
171
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 169

def transaction_joinable=(joinable)
  @transaction_joinable = joinable
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.



142
143
144
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 142

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