class ActiveRecord::ConnectionAdapters::AbstractAdapter
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 SchemaStatements are very useful.
Constants
- ADAPTER_NAME
- SIMPLE_INT
Attributes
Public Class Methods
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 88 def self.type_cast_config_to_boolean(config) if config == "false" false else config end end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 80 def self.type_cast_config_to_integer(config) if config =~ SIMPLE_INT config.to_i else config end end
Public Instance Methods
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.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 356 def active? end
Returns the human-readable name of the adapter. Use mixed case - one can always use downcase if needed.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 199 def adapter_name self.class::ADAPTER_NAME end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 421 def case_insensitive_comparison(table, attribute, column, value) if can_perform_case_insensitive_comparison_for?(column) table[attribute].lower.eq(table.lower(Arel::Nodes::BindParam.new)) else table[attribute].eq(Arel::Nodes::BindParam.new) end end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 413 def case_sensitive_comparison(table, attribute, column, value) if value.nil? table[attribute].eq(value) else table[attribute].eq(Arel::Nodes::BindParam.new) end end
Clear any caching the database adapter may be doing, for example clearing the prepared statement cache. This is database specific.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 387 def clear_cache! # this should be overridden by concrete adapters end
Check the connection back in to the connection pool
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 435 def close pool.checkin self end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 144 def collector if prepared_statements SQLString.new else BindCollector.new end end
This is meant to be implemented by the adapters that support extensions
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 313 def disable_extension(name) end
Override to turn off referential integrity while executing
&block
.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 347 def disable_referential_integrity yield end
Disconnects from the database if already connected. Otherwise, this method does nothing.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 369 def disconnect! clear_cache! reset_transaction end
This is meant to be implemented by the adapters that support extensions
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 317 def enable_extension(name) end
this method must only be called while holding connection pool's mutex
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 186 def expire @owner = nil end
A list of extensions, to be filled in by adapters that support them.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 335 def extensions [] end
A list of index algorithms, to be filled by adapters that support them.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 340 def index_algorithms {} end
this method must only be called while holding connection pool's mutex
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 165 def lease if in_use? msg = 'Cannot lease connection, ' if @owner == Thread.current msg << 'it is already leased by the current thread.' else msg << "it is already in use by a different thread: #{@owner}. " << "Current thread: #{Thread.current}." end raise ActiveRecordError, msg end @owner = Thread.current end
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.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 237 def prefetch_primary_key?(table_name = nil) false end
Provides access to the underlying database driver for this adapter. For example, this method returns a Mysql2::Client object in case of Mysql2Adapter, 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.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 409 def raw_connection @connection end
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.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 362 def reconnect! clear_cache! reset_transaction end
Returns true if its required to reload the connection between requests for development mode.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 392 def requires_reloading? false end
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.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 380 def reset! # this should be overridden by concrete adapters end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 180 def schema_cache=(cache) cache.connection = self @schema_cache = cache end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 160 def schema_creation SchemaCreation.new self end
Does this adapter support application-enforced advisory locking?
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 230 def supports_advisory_locks? false end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 220 def supports_bulk_alter? false end
Does this adapter support metadata comments on database objects (tables, columns, indexes)?
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 298 def supports_comments? false end
Can comments for tables, columns, and indexes be specified in create/alter table statements?
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 303 def supports_comments_in_create? false end
Does this adapter support datetime with precision?
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 288 def supports_datetime_with_precision? false end
Does this adapter support DDL rollbacks in transactions? That is, would CREATE TABLE or ALTER TABLE get rolled back by a transaction?
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 216 def supports_ddl_transactions? false end
Does this adapter support explain?
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 257 def supports_explain? false end
Does this adapter support expression indices?
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 252 def supports_expression_index? false end
Does this adapter support database extensions?
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 267 def supports_extensions? false end
Does this adapter support creating foreign key constraints?
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 278 def supports_foreign_keys? false end
Does this adapter support index sort order?
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 242 def supports_index_sort_order? false end
Does this adapter support creating indexes in the same statement as creating the table?
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 273 def supports_indexes_in_create? false end
Does this adapter support json data type?
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 293 def supports_json? false end
Does this adapter support migrations?
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 204 def supports_migrations? false end
Does this adapter support multi-value insert?
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 308 def supports_multi_insert? true end
Does this adapter support partial indices?
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 247 def supports_partial_index? false end
Can this adapter determine the primary key for tables not attached to an Active Record class, such as join tables?
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 210 def supports_primary_key? false end
Does this adapter support savepoints?
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 225 def supports_savepoints? false end
Does this adapter support setting the isolation level for a transaction?
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 262 def supports_transaction_isolation? false end
Does this adapter support views?
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 283 def supports_views? false end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 190 def unprepared_statement old_prepared_statements, @prepared_statements = @prepared_statements, false yield ensure @prepared_statements = old_prepared_statements end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 156 def valid_type?(type) false end
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.
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 399 def verify!(*ignored) reconnect! unless active? end
Protected Instance Methods
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 559 def log(sql, name = "SQL", binds = [], statement_name = nil) @instrumenter.instrument( "sql.active_record", :sql => sql, :name => name, :connection_id => object_id, :statement_name => statement_name, :binds => binds) { yield } rescue => e raise translate_exception_class(e, sql) end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 571 def translate_exception(exception, message) # override in derived class ActiveRecord::StatementInvalid.new(message) end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 547 def translate_exception_class(e, sql) begin message = "#{e.class.name}: #{e.message}: #{sql}" rescue Encoding::CompatibilityError message = "#{e.class.name}: #{e.message.force_encoding sql.encoding}: #{sql}" end exception = translate_exception(e, message) exception.set_backtrace e.backtrace exception end
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 576 def without_prepared_statement?(binds) !prepared_statements || binds.empty? end
Private Instance Methods
# File lib/active_record/connection_adapters/abstract_adapter.rb, line 429 def can_perform_case_insensitive_comparison_for?(column) true end