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.
- CLASS ActiveRecord::ConnectionAdapters::AbstractAdapter::BindCollector
- CLASS ActiveRecord::ConnectionAdapters::AbstractAdapter::SQLString
- CLASS ActiveRecord::ConnectionAdapters::AbstractAdapter::Version
- A
- C
- D
- E
- I
- L
- P
- R
- S
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- schema_cache=,
- schema_creation,
- supports_advisory_locks?,
- supports_bulk_alter?,
- supports_comments?,
- supports_comments_in_create?,
- supports_datetime_with_precision?,
- supports_ddl_transactions?,
- supports_explain?,
- supports_expression_index?,
- supports_extensions?,
- supports_foreign_keys?,
- supports_index_sort_order?,
- supports_indexes_in_create?,
- supports_json?,
- supports_migrations?,
- supports_multi_insert?,
- supports_partial_index?,
- supports_primary_key?,
- supports_savepoints?,
- supports_transaction_isolation?,
- supports_views?
- T
- U
- V
- W
- ActiveSupport::Callbacks
- ActiveRecord::ConnectionAdapters::Quoting
- ActiveRecord::ConnectionAdapters::DatabaseStatements
- ActiveRecord::ConnectionAdapters::SchemaStatements
- ActiveRecord::ConnectionAdapters::DatabaseLimits
- ActiveRecord::ConnectionAdapters::QueryCache
- ActiveRecord::ConnectionAdapters::ColumnDumper
- ActiveRecord::ConnectionAdapters::Savepoints
ADAPTER_NAME | = | "Abstract".freeze |
SIMPLE_INT | = | /\A\d+\z/ |
[R] | in_use? | |
[R] | logger | |
[R] | owner | |
[RW] | pool | |
[R] | prepared_statements | |
[R] | schema_cache | |
[RW] | visitor |
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 the human-readable name of the adapter. Use mixed case - one can always use downcase if needed.
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 444 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
Clear any caching the database adapter may be doing, for example clearing the prepared statement cache. This is database specific.
Check the connection back in to the connection pool
This is meant to be implemented by the adapters that support extensions
Override to turn off referential integrity while executing
&block
.
Disconnects from the database if already connected. Otherwise, this method does nothing.
This is meant to be implemented by the adapters that support extensions
this method must only be called while holding connection pool's mutex
# File activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 186 def expire if in_use? if @owner != Thread.current raise ActiveRecordError, "Cannot expire connection, " << "it is owned by a different thread: #{@owner}. " << "Current thread: #{Thread.current}." end @owner = nil else raise ActiveRecordError, 'Cannot expire connection, it is not currently leased.' end end
A list of extensions, to be filled in by adapters that support them.
A list of index algorithms, to be filled by adapters that support them.
this method must only be called while holding connection pool's mutex
# File activerecord/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.
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.
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.
Returns true if its required to reload the connection between requests for development mode.
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.
Does this adapter support application-enforced advisory locking?
Does this adapter support metadata comments on database objects (tables, columns, indexes)?
Can comments for tables, columns, and indexes be specified in create/alter table statements?
Does this adapter support datetime with precision?
Does this adapter support DDL rollbacks in transactions? That is, would CREATE TABLE or ALTER TABLE get rolled back by a transaction?
Does this adapter support explain?
Does this adapter support expression indices?
Does this adapter support database extensions?
Does this adapter support creating foreign key constraints?
Does this adapter support index sort order?
Does this adapter support creating indexes in the same statement as creating the table?
Does this adapter support json data type?
Does this adapter support migrations?
Does this adapter support multi-value insert?
Does this adapter support partial indices?
Can this adapter determine the primary key for tables not attached to an Active Record class, such as join tables?
Does this adapter support savepoints?
Does this adapter support setting the isolation level for a transaction?
Does this adapter support views?
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 activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 582 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 activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 570 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