Class: ActiveRecord::ConnectionAdapters::AbstractAdapter
- Inherits:
-
Object
- Object
- ActiveRecord::ConnectionAdapters::AbstractAdapter
- Includes:
- DatabaseLimits, DatabaseStatements, Quoting, SchemaStatements, QueryCache, ActiveSupport::Callbacks
- Defined in:
- activerecord/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 Method Summary (collapse)
-
- (Boolean) active?
Checks whether the connection to the database is still active.
-
- (Object) adapter_name
Returns the human-readable name of the adapter.
- - (Object) create_savepoint
- - (Object) current_savepoint_name
- - (Object) decrement_open_transactions
-
- (Object) disable_referential_integrity
Override to turn off referential integrity while executing &block.
-
- (Object) disconnect!
Disconnects from the database if already connected.
- - (Object) increment_open_transactions
-
- (AbstractAdapter) initialize(connection, logger = nil)
constructor
:nodoc:.
- - (Object) open_transactions
-
- (Boolean) prefetch_primary_key?(table_name = nil)
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.
-
- (Object) quote_table_name(name)
Override to return the quoted table name.
-
- (Object) raw_connection
Provides access to the underlying database driver for this adapter.
-
- (Object) reconnect!
Disconnects from the database if already connected, and establishes a new connection with the database.
- - (Object) release_savepoint
-
- (Boolean) requires_reloading?
Returns true if its required to reload the connection between requests for development mode.
-
- (Object) reset!
Reset the state of this connection, directing the DBMS to clear transactions and other connection-related server-side state.
- - (Object) rollback_to_savepoint
-
- (Boolean) supports_count_distinct?
Does this adapter support using DISTINCT within COUNT? This is true for all adapters except sqlite.
-
- (Boolean) supports_ddl_transactions?
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.
-
- (Boolean) supports_migrations?
Does this adapter support migrations? Backend specific, as the abstract adapter always returns false.
-
- (Boolean) supports_primary_key?
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.
-
- (Boolean) supports_savepoints?
Does this adapter support savepoints? PostgreSQL and MySQL do, SQLite does not.
- - (Object) transaction_joinable=(joinable)
-
- (Object) verify!(*ignored)
Checks whether the connection to the database is still active (i.e. not stale).
Methods included from ActiveSupport::Callbacks
Methods included from ActiveSupport::Concern
#append_features, extended, #included
Methods inherited from QueryCache
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 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
Methods included from DatabaseStatements
#add_limit_offset!, #add_transaction_record, #begin_db_transaction, #case_sensitive_equality_operator, #commit_db_transaction, #default_sequence_name, #delete, #empty_insert_statement_value, #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 Quoting
#quote, #quote_column_name, #quote_string, #quoted_date, #quoted_false, #quoted_true
Constructor Details
- (AbstractAdapter) initialize(connection, logger = nil)
:nodoc:
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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 39 def initialize(connection, logger = nil) #:nodoc: @active = nil @connection, @logger = connection, logger @query_cache_enabled = false @query_cache = {} @instrumenter = ActiveSupport::Notifications.instrumenter end |
Instance Method Details
- (Boolean) active?
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.
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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 112 def active? @active != false end |
- (Object) adapter_name
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 49 def adapter_name 'Abstract' end |
- (Object) create_savepoint
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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 178 def create_savepoint end |
- (Object) current_savepoint_name
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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 187 def current_savepoint_name "active_record_#{open_transactions}" end |
- (Object) decrement_open_transactions
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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 170 def decrement_open_transactions @open_transactions -= 1 end |
- (Object) disable_referential_integrity
Override to turn off referential integrity while executing &block.
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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 103 def disable_referential_integrity yield end |
- (Object) disconnect!
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 124 def disconnect! @active = false end |
- (Object) increment_open_transactions
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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 165 def increment_open_transactions @open_transactions ||= 0 @open_transactions += 1 end |
- (Object) open_transactions
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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 161 def open_transactions @open_transactions ||= 0 end |
- (Boolean) prefetch_primary_key?(table_name = nil)
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.
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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 89 def prefetch_primary_key?(table_name = nil) false end |
- (Object) quote_table_name(name)
Override to return the quoted table name. Defaults to column quoting.
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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 96 def quote_table_name(name) quote_column_name(name) end |
- (Object) raw_connection
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 157 def raw_connection @connection end |
- (Object) reconnect!
Disconnects from the database if already connected, and establishes a new connection with the database.
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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 118 def reconnect! @active = true end |
- (Object) release_savepoint
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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 184 def release_savepoint end |
- (Boolean) requires_reloading?
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.
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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 140 def requires_reloading? false end |
- (Object) reset!
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 134 def reset! # this should be overridden by concrete adapters end |
- (Object) rollback_to_savepoint
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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 181 def rollback_to_savepoint end |
- (Boolean) supports_count_distinct?
Does this adapter support using DISTINCT within COUNT? This is true for all adapters except sqlite.
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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 68 def supports_count_distinct? true end |
- (Boolean) supports_ddl_transactions?
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.
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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 75 def supports_ddl_transactions? false end |
- (Boolean) supports_migrations?
Does this adapter support migrations? Backend specific, as the abstract adapter always returns false.
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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 55 def supports_migrations? false end |
- (Boolean) supports_primary_key?
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.
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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 62 def supports_primary_key? false end |
- (Boolean) supports_savepoints?
Does this adapter support savepoints? PostgreSQL and MySQL do, SQLite does not.
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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 81 def supports_savepoints? false end |
- (Object) transaction_joinable=(joinable)
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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 174 def transaction_joinable=(joinable) @transaction_joinable = joinable end |
- (Object) verify!(*ignored)
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 147 def verify!(*ignored) reconnect! unless active? end |