Class: ActiveRecord::ConnectionAdapters::AbstractAdapter

Inherits:
Object
  • Object
show all
Includes:
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.

Instance Attribute Summary collapse

Attributes included from QueryCache

#query_cache, #query_cache_enabled

Instance Method Summary collapse

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

#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, #quoted_date, #quoted_false, #quoted_true, #type_cast

Methods included from DatabaseStatements

#add_transaction_record, #begin_db_transaction, #case_sensitive_equality_operator, #commit_db_transaction, #default_sequence_name, #delete, #empty_insert_statement_value, #exec_delete, #exec_insert, #exec_query, #exec_update, #execute, #insert, #insert_fixture, #join_to_update, #limited_update_conditions, #outside_transaction?, #reset_sequence!, #rollback_db_transaction, #sanitize_limit, #select_all, #select_one, #select_rows, #select_value, #select_values, #supports_statement_cache?, #to_sql, #transaction, #update

Methods included from SchemaStatements

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

Constructor Details

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

:nodoc:



60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 60

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

  @active              = nil
  @connection          = connection
  @in_use              = false
  @instrumenter        = ActiveSupport::Notifications.instrumenter
  @last_use            = false
  @logger              = logger
  @open_transactions   = 0
  @pool                = pool
  @query_cache         = Hash.new { |h,sql| h[sql] = {} }
  @query_cache_enabled = false
  @schema_cache        = SchemaCache.new self
  @visitor             = nil
end

Instance Attribute Details

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

Returns the value of attribute in_use.



57
58
59
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 57

def in_use
  @in_use
end

#last_use ⇒ Object (readonly)

Returns the value of attribute last_use.



57
58
59
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 57

def last_use
  @last_use
end

#logger ⇒ Object (readonly)

Returns the value of attribute logger.



57
58
59
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 57

def logger
  @logger
end

#open_transactions ⇒ Object (readonly)

Returns the value of attribute open_transactions.



232
233
234
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 232

def open_transactions
  @open_transactions
end

#pool ⇒ Object

Returns the value of attribute pool.



56
57
58
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 56

def pool
  @pool
end

#schema_cache ⇒ Object (readonly)

Returns the value of attribute schema_cache.



57
58
59
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 57

def schema_cache
  @schema_cache
end

#visitor ⇒ Object

Returns the value of attribute visitor.



56
57
58
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 56

def visitor
  @visitor
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) 


176
177
178
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 176

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.



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

def adapter_name
  'Abstract'
end

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



259
260
261
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 259

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

#case_sensitive_modifier(node) ⇒ Object 



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

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.



205
206
207
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 205

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

#close ⇒ Object

Check the connection back in to the connection pool



268
269
270
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 268

def close
  pool.checkin self
end

#create_savepoint ⇒ Object 



246
247
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 246

def create_savepoint
end

#current_savepoint_name ⇒ Object 



263
264
265
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 263

def current_savepoint_name
  "active_record_#{open_transactions}"
end

#decrement_open_transactions ⇒ Object 



238
239
240
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 238

def decrement_open_transactions
  @open_transactions -= 1
end

#disable_referential_integrity ⇒ Object

Override to turn off referential integrity while executing &block.



167
168
169
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 167

def disable_referential_integrity
  yield
end

#disconnect! ⇒ Object

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



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

def disconnect!
  @active = false
end

#expire ⇒ Object 



86
87
88
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 86

def expire
  @in_use = false
end

#increment_open_transactions ⇒ Object 



234
235
236
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 234

def increment_open_transactions
  @open_transactions += 1
end

#lease ⇒ Object 



77
78
79
80
81
82
83
84
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 77

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


136
137
138
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 136

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.



154
155
156
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 154

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.



228
229
230
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 228

def raw_connection
  @connection
end

#reconnect! ⇒ Object

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



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

def reconnect!
  @active = true
end

#release_savepoint ⇒ Object 



252
253
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 252

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) 


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

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.



198
199
200
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 198

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

#rollback_to_savepoint ⇒ Object 



249
250
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 249

def rollback_to_savepoint
end

#substitute_at(column, index) ⇒ Object

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



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

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

#supports_bulk_alter? ⇒ Boolean

Returns:

  • (Boolean) 


122
123
124
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 122

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) 


111
112
113
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 111

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) 


118
119
120
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 118

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) 


147
148
149
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 147

def supports_explain?
  false
end

#supports_index_sort_order? ⇒ Boolean

Does this adapter support index sort order?

Returns:

  • (Boolean) 


141
142
143
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 141

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) 


98
99
100
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 98

def supports_migrations?
  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) 


105
106
107
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 105

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) 


128
129
130
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 128

def supports_savepoints?
  false
end

#transaction_joinable=(joinable) ⇒ Object 



242
243
244
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 242

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.



218
219
220
 
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 218

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