Module: ActiveRecord::ConnectionAdapters::DatabaseStatements
Relationships & Source Files | |
Extension / Inclusion / Inheritance Descendants | |
Included In:
| |
Defined in: | activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb |
Constant Summary
-
DEFAULT_INSERT_VALUE =
private
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 534Arel.sql("DEFAULT").freeze
Instance Attribute Summary
- #begin_transaction readonly
- #commit_transaction readonly
- #current_transaction readonly
- #dirty_current_transaction readonly
- #materialize_transactions readonly
- #open_transactions readonly
- #rollback_transaction readonly
- #transaction_open? ⇒ Boolean readonly
- #within_new_transaction readonly
Instance Method Summary
-
#add_transaction_record(record, ensure_finalize = true)
Register a record with the current transaction so that its after_commit and after_rollback callbacks can be called.
-
#begin_db_transaction
Begins the transaction (and turns off auto-committing).
-
#begin_isolated_db_transaction(isolation)
Begins the transaction with the isolation level set.
-
#commit_db_transaction
Commits the transaction (and turns on auto-committing).
-
#create(arel, name = nil, pk = nil, id_value = nil, sequence_name = nil, binds = [], returning: nil)
Alias for #insert.
- #default_sequence_name(table, column)
-
#delete(arel, name = nil, binds = [])
Executes the delete statement and returns the number of rows affected.
- #disable_lazy_transactions!
- #empty_insert_statement_value(primary_key = nil)
- #enable_lazy_transactions!
-
#exec_delete(sql, name = nil, binds = [])
Executes delete
sql
statement in the context of this connection usingbinds
as the bind substitutes. -
#exec_insert(sql, name = nil, binds = [], pk = nil, sequence_name = nil, returning: nil)
Executes insert
sql
statement in the context of this connection usingbinds
as the bind substitutes. -
#exec_query(sql, name = "SQL", binds = [], prepare: false)
Executes
sql
statement in the context of this connection usingbinds
as the bind substitutes. -
#exec_update(sql, name = nil, binds = [])
Executes update
sql
statement in the context of this connection usingbinds
as the bind substitutes. -
#execute(sql, name = nil, allow_retry: false)
Executes the SQL statement in the context of this connection and returns the raw result from the connection adapter.
-
#high_precision_current_timestamp
Returns an
::Arel
SQL literal for the CURRENT_TIMESTAMP for usage with arbitrary precision date/time columns. - #initialize
-
#insert(arel, name = nil, pk = nil, id_value = nil, sequence_name = nil, binds = [], returning: nil)
(also: #create)
Executes an INSERT query and returns the new record’s ID.
-
#insert_fixture(fixture, table_name)
Inserts the given fixture into the table.
- #insert_fixtures_set(fixture_set, tables_to_delete = [])
-
#reset_sequence!(table, column, sequence = nil)
Set the sequence to the max value of the table’s column.
- #restart_db_transaction
-
#rollback_db_transaction
Rolls back the transaction (and turns on auto-committing).
- #rollback_to_savepoint(name = nil)
-
#sanitize_limit(limit)
Sanitizes the given LIMIT parameter in order to prevent SQL injection.
-
#select_all(arel, name = nil, binds = [], preparable: nil, async: false)
Returns an
::ActiveRecord::Result
instance. -
#select_one(arel, name = nil, binds = [], async: false)
Returns a record hash with the column names as keys and column values as values.
-
#select_rows(arel, name = nil, binds = [], async: false)
Returns an array of arrays containing the field values.
-
#select_value(arel, name = nil, binds = [], async: false)
Returns a single value from a record.
-
#select_values(arel, name = nil, binds = [])
Returns an array of the values of the first column in a select:
-
#to_sql(arel_or_sql_string, binds = [])
Converts an arel AST to SQL.
-
#transaction(requires_new: nil, isolation: nil, joinable: true, &block)
Runs the given block in a database transaction, and returns the result of the block.
- #transaction_isolation_levels
-
#truncate(table_name, name = nil)
Executes the truncate statement.
-
#update(arel, name = nil, binds = [])
Executes the update statement and returns the number of rows affected.
-
#write_query?(sql) ⇒ Boolean
Determines whether the SQL statement is a write query.
Instance Attribute Details
#begin_transaction (readonly)
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 352
delegate :within_new_transaction, :open_transactions, :current_transaction, :begin_transaction, :commit_transaction, :rollback_transaction, :materialize_transactions, :disable_lazy_transactions!, :enable_lazy_transactions!, :dirty_current_transaction, to: :transaction_manager
#commit_transaction (readonly)
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 352
delegate :within_new_transaction, :open_transactions, :current_transaction, :begin_transaction, :commit_transaction, :rollback_transaction, :materialize_transactions, :disable_lazy_transactions!, :enable_lazy_transactions!, :dirty_current_transaction, to: :transaction_manager
#current_transaction (readonly)
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 352
delegate :within_new_transaction, :open_transactions, :current_transaction, :begin_transaction, :commit_transaction, :rollback_transaction, :materialize_transactions, :disable_lazy_transactions!, :enable_lazy_transactions!, :dirty_current_transaction, to: :transaction_manager
#dirty_current_transaction (readonly)
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 352
delegate :within_new_transaction, :open_transactions, :current_transaction, :begin_transaction, :commit_transaction, :rollback_transaction, :materialize_transactions, :disable_lazy_transactions!, :enable_lazy_transactions!, :dirty_current_transaction, to: :transaction_manager
#materialize_transactions (readonly)
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 352
delegate :within_new_transaction, :open_transactions, :current_transaction, :begin_transaction, :commit_transaction, :rollback_transaction, :materialize_transactions, :disable_lazy_transactions!, :enable_lazy_transactions!, :dirty_current_transaction, to: :transaction_manager
#open_transactions (readonly)
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 352
delegate :within_new_transaction, :open_transactions, :current_transaction, :begin_transaction, :commit_transaction, :rollback_transaction, :materialize_transactions, :disable_lazy_transactions!, :enable_lazy_transactions!, :dirty_current_transaction, to: :transaction_manager
#rollback_transaction (readonly)
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 352
delegate :within_new_transaction, :open_transactions, :current_transaction, :begin_transaction, :commit_transaction, :rollback_transaction, :materialize_transactions, :disable_lazy_transactions!, :enable_lazy_transactions!, :dirty_current_transaction, to: :transaction_manager
#transaction_open? ⇒ Boolean
(readonly)
[ GitHub ]
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 364
def transaction_open? current_transaction.open? end
#within_new_transaction (readonly)
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 352
delegate :within_new_transaction, :open_transactions, :current_transaction, :begin_transaction, :commit_transaction, :rollback_transaction, :materialize_transactions, :disable_lazy_transactions!, :enable_lazy_transactions!, :dirty_current_transaction, to: :transaction_manager
Instance Method Details
#add_transaction_record(record, ensure_finalize = true)
Register a record with the current transaction so that its after_commit and after_rollback callbacks can be called.
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 390
def add_transaction_record(record, ensure_finalize = true) current_transaction.add_record(record, ensure_finalize) end
#begin_db_transaction
Begins the transaction (and turns off auto-committing).
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 395
def begin_db_transaction() end
#begin_isolated_db_transaction(isolation)
Begins the transaction with the isolation level set. Raises an error by default; adapters that support setting the isolation level should implement this method.
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 409
def begin_isolated_db_transaction(isolation) raise ActiveRecord::TransactionIsolationError, "adapter does not support setting transaction isolation" end
#commit_db_transaction
Commits the transaction (and turns on auto-committing).
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 414
def commit_db_transaction() end
#create(arel, name = nil, pk = nil, id_value = nil, sequence_name = nil, binds = [], returning: nil)
Alias for #insert.
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 197
alias create insert
#default_sequence_name(table, column)
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 436
def default_sequence_name(table, column) nil end
#delete(arel, name = nil, binds = [])
Executes the delete statement and returns the number of rows affected.
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 206
def delete(arel, name = nil, binds = []) sql, binds = to_sql_and_binds(arel, binds) exec_delete(sql, name, binds) end
#disable_lazy_transactions!
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 352
delegate :within_new_transaction, :open_transactions, :current_transaction, :begin_transaction, :commit_transaction, :rollback_transaction, :materialize_transactions, :disable_lazy_transactions!, :enable_lazy_transactions!, :dirty_current_transaction, to: :transaction_manager
#empty_insert_statement_value(primary_key = nil)
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 468
def empty_insert_statement_value(primary_key = nil) "DEFAULT VALUES" end
#enable_lazy_transactions!
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 352
delegate :within_new_transaction, :open_transactions, :current_transaction, :begin_transaction, :commit_transaction, :rollback_transaction, :materialize_transactions, :disable_lazy_transactions!, :enable_lazy_transactions!, :dirty_current_transaction, to: :transaction_manager
#exec_delete(sql, name = nil, binds = [])
Executes delete sql
statement in the context of this connection using binds
as the bind substitutes. name
is logged along with the executed sql
statement.
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 159
def exec_delete(sql, name = nil, binds = []) internal_exec_query(sql, name, binds) end
#exec_insert(sql, name = nil, binds = [], pk = nil, sequence_name = nil, returning: nil)
Executes insert sql
statement in the context of this connection using binds
as the bind substitutes. name
is logged along with the executed sql
statement. Some adapters support the returning
keyword argument which allows to control the result of the query: nil
is the default value and maintains default behavior. If an array of column names is passed - the result will contain values of the specified columns from the inserted row.
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 151
def exec_insert(sql, name = nil, binds = [], pk = nil, sequence_name = nil, returning: nil) sql, binds = sql_for_insert(sql, pk, binds, returning) internal_exec_query(sql, name, binds) end
#exec_query(sql, name = "SQL", binds = [], prepare: false)
Executes sql
statement in the context of this connection using binds
as the bind substitutes. name
is logged along with the executed sql
statement.
Note: the query is assumed to have side effects and the query cache will be cleared. If the query is read-only, consider using #select_all instead.
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 141
def exec_query(sql, name = "SQL", binds = [], prepare: false) internal_exec_query(sql, name, binds, prepare: prepare) end
#exec_update(sql, name = nil, binds = [])
Executes update sql
statement in the context of this connection using binds
as the bind substitutes. name
is logged along with the executed sql
statement.
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 166
def exec_update(sql, name = nil, binds = []) internal_exec_query(sql, name, binds) end
#execute(sql, name = nil, allow_retry: false)
Executes the SQL statement in the context of this connection and returns the raw result from the connection adapter.
Setting allow_retry
to true causes the db to reconnect and retry executing the SQL statement in case of a connection-related exception. This option should only be enabled for known idempotent queries.
Note: the query is assumed to have side effects and the query cache will be cleared. If the query is read-only, consider using #select_all instead.
Note: depending on your database connector, the result returned by this method may be manually memory managed. Consider using #exec_query wrapper instead.
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 130
def execute(sql, name = nil, allow_retry: false) internal_execute(sql, name, allow_retry: allow_retry) end
#high_precision_current_timestamp
Returns an ::Arel
SQL literal for the CURRENT_TIMESTAMP for usage with arbitrary precision date/time columns.
Adapters supporting datetime with precision should override this to provide as much precision as is available.
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 506
def HIGH_PRECISION_CURRENT_TIMESTAMP end
#initialize
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 6
def initialize super reset_transaction end
#insert(arel, name = nil, pk = nil, id_value = nil, sequence_name = nil, binds = [], returning: nil) Also known as: #create
Executes an INSERT query and returns the new record’s ID
id_value
will be returned unless the value is nil
, in which case the database will attempt to calculate the last inserted id and return that value.
If the next id was calculated in advance (as in Oracle), it should be passed in as id_value
. Some adapters support the returning
keyword argument which allows defining the return value of the method: nil
is the default value and maintains default behavior. If an array of column names is passed - an array of is returned from the method representing values of the specified columns from the inserted row.
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 189
def insert(arel, name = nil, pk = nil, id_value = nil, sequence_name = nil, binds = [], returning: nil) sql, binds = to_sql_and_binds(arel, binds) value = exec_insert(sql, name, binds, pk, sequence_name, returning: returning) return returning_column_values(value) unless returning.nil? id_value || last_inserted_id(value) end
#insert_fixture(fixture, table_name)
Inserts the given fixture into the table. Overridden in adapters that require something beyond a simple insert (e.g. Oracle). Most of adapters should implement #insert_fixtures_set that leverages bulk SQL insert. We keep this method to provide fallback for databases like SQLite that do not support bulk inserts.
#insert_fixtures_set(fixture_set, tables_to_delete = [])
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 454
def insert_fixtures_set(fixture_set, tables_to_delete = []) fixture_inserts = build_fixture_statements(fixture_set) table_deletes = tables_to_delete.map { |table| "DELETE FROM #{quote_table_name(table)}" } statements = table_deletes + fixture_inserts with_multi_statements do disable_referential_integrity do transaction(requires_new: true) do execute_batch(statements, "Fixtures Load") end end end end
#reset_sequence!(table, column, sequence = nil)
Set the sequence to the max value of the table’s column.
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 441
def reset_sequence!(table, column, sequence = nil) # Do nothing by default. Implement for PostgreSQL, Oracle, ... end
#restart_db_transaction
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 426
def restart_db_transaction exec_restart_db_transaction end
#rollback_db_transaction
Rolls back the transaction (and turns on auto-committing). Must be done if the transaction block raises an exception or returns false.
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 418
def rollback_db_transaction exec_rollback_db_transaction rescue ActiveRecord::ConnectionNotEstablished, ActiveRecord::ConnectionFailed # Connection's gone; that counts as a rollback end
#rollback_to_savepoint(name = nil)
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 432
def rollback_to_savepoint(name = nil) exec_rollback_to_savepoint(name) end
#sanitize_limit(limit)
Sanitizes the given LIMIT parameter in order to prevent SQL injection.
The limit
may be anything that can evaluate to a string via #to_s
. It should look like an integer, or an ::Arel
SQL literal.
Returns Integer and ::Arel::Nodes::SqlLiteral
limits as is.
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 478
def sanitize_limit(limit) if limit.is_a?(Integer) || limit.is_a?(Arel::Nodes::SqlLiteral) limit else Integer(limit) end end
#select_all(arel, name = nil, binds = [], preparable: nil, async: false)
Returns an ::ActiveRecord::Result
instance.
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 67
def select_all(arel, name = nil, binds = [], preparable: nil, async: false) arel = arel_from_relation(arel) sql, binds, preparable = to_sql_and_binds(arel, binds, preparable) select(sql, name, binds, prepare: prepared_statements && preparable, async: async && FutureResult::SelectAll) rescue ::RangeError ActiveRecord::Result.empty(async: async) end
#select_one(arel, name = nil, binds = [], async: false)
Returns a record hash with the column names as keys and column values as values.
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 78
def select_one(arel, name = nil, binds = [], async: false) select_all(arel, name, binds, async: async).then(&:first) end
#select_rows(arel, name = nil, binds = [], async: false)
Returns an array of arrays containing the field values. Order is the same as that returned by columns
.
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 95
def select_rows(arel, name = nil, binds = [], async: false) select_all(arel, name, binds, async: async).then(&:rows) end
#select_value(arel, name = nil, binds = [], async: false)
Returns a single value from a record
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 83
def select_value(arel, name = nil, binds = [], async: false) select_rows(arel, name, binds, async: async).then { |rows| single_value_from_rows(rows) } end
#select_values(arel, name = nil, binds = [])
Returns an array of the values of the first column in a select:
select_values("SELECT id FROM companies LIMIT 3") => [1,2,3]
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 89
def select_values(arel, name = nil, binds = []) select_rows(arel, name, binds).map(&:first) end
#to_sql(arel_or_sql_string, binds = [])
Converts an arel AST to SQL
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 12
def to_sql(arel_or_sql_string, binds = []) sql, _ = to_sql_and_binds(arel_or_sql_string, binds) sql end
#transaction(requires_new: nil, isolation: nil, joinable: true, &block)
Runs the given block in a database transaction, and returns the result of the block.
Nested transactions support
#transaction
calls can be nested. By default, this makes all database statements in the nested transaction block become part of the parent transaction. For example, the following behavior may be surprising:
ActiveRecord::Base.transaction do
Post.create(title: 'first')
ActiveRecord::Base.transaction do
Post.create(title: 'second')
raise ActiveRecord::Rollback
end
end
This creates both “first” and “second” posts. Reason is the ::ActiveRecord::Rollback
exception in the nested block does not issue a ROLLBACK. Since these exceptions are captured in transaction blocks, the parent block does not see it and the real transaction is committed.
Most databases don’t support true nested transactions. At the time of writing, the only database that supports true nested transactions that we’re aware of, is MS-SQL.
In order to get around this problem, #transaction
will emulate the effect of nested transactions, by using savepoints: dev.mysql.com/doc/refman/en/savepoint.html.
It is safe to call this method if a database transaction is already open, i.e. if #transaction
is called within another #transaction
block. In case of a nested call, #transaction
will behave as follows:
-
The block will be run without doing anything. All database statements that happen within the block are effectively appended to the already open database transaction.
-
However, if
:requires_new
is set, the block will be wrapped in a database savepoint acting as a sub-transaction.
In order to get a ROLLBACK for the nested transaction you may ask for a real sub-transaction by passing requires_new: true
. If anything goes wrong, the database rolls back to the beginning of the sub-transaction without rolling back the parent transaction. If we add it to the previous example:
ActiveRecord::Base.transaction do
Post.create(title: 'first')
ActiveRecord::Base.transaction(requires_new: true) do
Post.create(title: 'second')
raise ActiveRecord::Rollback
end
end
only post with title “first” is created.
See ::ActiveRecord::Transactions
to learn more.
Caveats
MySQL
doesn’t support DDL transactions. If you perform a DDL operation, then any created savepoints will be automatically released. For example, if you’ve created a savepoint, then you execute a CREATE TABLE statement, then the savepoint that was created will be automatically released.
This means that, on MySQL
, you shouldn’t execute DDL operations inside a #transaction
call that you know might create a savepoint. Otherwise, #transaction
will raise exceptions when it tries to release the already-automatically-released savepoints:
Model.connection.transaction do # BEGIN
Model.connection.transaction(requires_new: true) do # CREATE SAVEPOINT active_record_1
Model.connection.create_table(...)
# active_record_1 now automatically released
end # RELEASE SAVEPOINT active_record_1 <--- BOOM! database error!
end
Transaction isolation
If your database supports setting the isolation level for a transaction, you can set it like so:
Post.transaction(isolation: :serializable) do
# ...
end
Valid isolation levels are:
-
:read_uncommitted
-
:read_committed
-
:repeatable_read
-
:serializable
You should consult the documentation for your database to understand the semantics of these different levels:
An ::ActiveRecord::TransactionIsolationError
will be raised if:
-
The adapter does not support setting the isolation level
-
You are joining an existing open transaction
-
You are creating a nested (savepoint) transaction
The mysql2, trilogy, and postgresql adapters support setting the transaction isolation level.
:args: (requires_new: nil, isolation: nil, &block)
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 337
def transaction(requires_new: nil, isolation: nil, joinable: true, &block) if !requires_new && current_transaction.joinable? if isolation raise ActiveRecord::TransactionIsolationError, "cannot set isolation when joining a transaction" end yield else transaction_manager.within_new_transaction(isolation: isolation, joinable: joinable, &block) end rescue ActiveRecord::Rollback # rollbacks are silently swallowed end
#transaction_isolation_levels
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 397
def transaction_isolation_levels { read_uncommitted: "READ UNCOMMITTED", read_committed: "READ COMMITTED", repeatable_read: "REPEATABLE READ", serializable: "SERIALIZABLE" } end
#truncate(table_name, name = nil)
Executes the truncate statement.
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 212
def truncate(table_name, name = nil) execute(build_truncate_statement(table_name), name) end
#update(arel, name = nil, binds = [])
Executes the update statement and returns the number of rows affected.
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 200
def update(arel, name = nil, binds = []) sql, binds = to_sql_and_binds(arel, binds) exec_update(sql, name, binds) end
#write_query?(sql) ⇒ Boolean
Determines whether the SQL statement is a write query.
# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 112
def write_query?(sql) raise NotImplementedError end