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Class Public methods

new()

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 6
def initialize
  super
  reset_transaction
end

Instance Public methods

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.

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 562
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).

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 567
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.

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 592
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).

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 606
def commit_db_transaction()   end

create(arel_or_sql, name = nil, pk = nil, id_value = nil, sequence_name = nil, binds = [], returning: nil)

Alias for: insert

default_sequence_name(table, column)

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 628
def default_sequence_name(table, column)
  nil
end

delete(arel_or_sql, name = nil, binds = [])

Executes the delete statement and returns the number of rows affected.

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 342
      def delete(arel_or_sql, name = nil, binds = [])
        if binds.any?
          ActiveRecord.deprecator.warn(<<~MSG.squish)
            Passing `binds` as a positional argument to `delete` is
            deprecated and will be removed in Rails 9.0. Use
            `Arel.sql(sql_with_placeholders, *binds)` to carry bind values
            inside the arel node instead —
            `delete(sql, name, binds)` becomes
            `delete(Arel.sql(sql, *binds), name)`.
          MSG
        end

        intent = QueryIntent.new(adapter: self, arel: arel_or_sql, name: name, binds: binds)

        intent.execute!
        intent.affected_rows
      end

empty_insert_statement_value(primary_key = nil)

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 662
def empty_insert_statement_value(primary_key = nil)
  "DEFAULT VALUES"
end

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.

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 217
def exec_delete(sql, name = nil, binds = [])
  intent = internal_build_intent(sql, name, binds)
  intent.execute!
  intent.affected_rows
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.

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 193
def exec_insert(sql, name = nil, binds = [], pk = nil, sequence_name = nil, returning: nil)
  # The `pk` positional argument is really the RETURNING column name.
  # Translate it to `returning:` — including the legacy `false` sentinel
  # meaning "no primary key / skip RETURNING".
  if pk == false
    returning ||= []
  elsif pk
    returning ||= pk
  end

  intent = QueryIntent.new(adapter: self, raw_sql: sql, name: name, binds: binds)

  _exec_insert(intent, sequence_name, returning: returning)
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.

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 181
def exec_query(sql, name = "SQL", binds = [], prepare: false)
  intent = internal_build_intent(sql, name, binds, prepare: prepare)
  intent.execute!
  intent.cast_result
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.

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 226
def exec_update(sql, name = nil, binds = [])
  intent = internal_build_intent(sql, name, binds)
  intent.execute!
  intent.affected_rows
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.

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 168
def execute(sql, name = nil, allow_retry: false)
  intent = internal_build_intent(sql, name, allow_retry: allow_retry)
  intent.execute!
  intent.raw_result
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.

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 686
def high_precision_current_timestamp
  HIGH_PRECISION_CURRENT_TIMESTAMP
end

insert(arel_or_sql, name = nil, pk = nil, id_value = nil, sequence_name = nil, binds = [], returning: nil)

Executes an INSERT query and returns the new record’s ID.

Some adapters support the ‘returning` keyword argument, which controls what the method returns: nil (default) returns the id via last_inserted_id; a column name returns that column as a single value; an array of column names returns an Array of column values.

Also aliased as: create

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 250
      def insert(arel_or_sql, name = nil, pk = nil, id_value = nil, sequence_name = nil, binds = [], returning: nil)
        unless pk.nil?
          ActiveRecord.deprecator.warn(<<~MSG.squish)
            Passing `pk` as a positional argument to `insert` is deprecated
            and will be removed in Rails 9.0. Pass `returning:` instead —
            `insert(arel, name, "id")` becomes `insert(arel, name, returning: "id")`.
          MSG
        end
        unless id_value.nil?
          ActiveRecord.deprecator.warn(<<~MSG.squish)
            Passing `id_value` as a positional argument to `insert` is
            deprecated and will be removed in Rails 9.0. `id_value` was
            returned when the database couldn't compute the last inserted id;
            callers that pass it already know the value and can use it
            directly rather than reading it back from `insert`.
          MSG
        end
        unless sequence_name.nil?
          ActiveRecord.deprecator.warn(<<~MSG.squish)
            Passing `sequence_name` as a positional argument to `insert` is
            deprecated and will be removed in Rails 9.0. It was only used by
            PostgreSQL's `use_insert_returning?` currval fallback, which is
            deprecated on its own — drop the argument once the
            `insert_returning` option is removed.
          MSG
        end
        if binds.any?
          ActiveRecord.deprecator.warn(<<~MSG.squish)
            Passing `binds` as a positional argument to `insert` is
            deprecated and will be removed in Rails 9.0. Use
            `Arel.sql(sql_with_placeholders, *binds)` to carry bind values
            inside the arel node instead —
            `insert(sql, name, nil, nil, nil, binds)` becomes
            `insert(Arel.sql(sql, *binds), name)`.
          MSG
        end

        # The `pk` positional argument is really the RETURNING column name.
        # Translate it to `returning:` — including the legacy `false` sentinel
        # meaning "no primary key / skip RETURNING".
        if pk == false
          returning ||= []
        elsif pk
          returning ||= pk
        end

        intent = QueryIntent.new(adapter: self, arel: arel_or_sql, name: name, binds: binds)

        value = _exec_insert(intent, sequence_name, returning: returning)

        case returning
        when nil
          id_value || last_inserted_id(value)
        when Array
          returning_column_values(value)
        else
          returning_column_values(value)&.first
        end
      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.

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 642
def insert_fixture(fixture, table_name)
  execute(build_fixture_sql(Array.wrap(fixture), table_name), "Fixture Insert")
end

insert_fixtures_set(fixture_set, tables_to_delete = [])

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 646
def insert_fixtures_set(fixture_set, tables_to_delete = [])
  fixture_inserts = build_fixture_statements(fixture_set)
  table_deletes = build_delete_from_statements(tables_to_delete)
  statements = table_deletes + fixture_inserts

  transaction(requires_new: true) do
    disable_referential_integrity do
      execute_batch(statements, "Fixtures Load")
    end
  end
end

reset_isolation_level()

Hook point called after an isolated DB transaction is committed or rolled back. Most adapters don’t need to implement anything because the isolation level is set on a per transaction basis. But some databases like SQLite set it on a per connection level and need to explicitly reset it after commit or rollback.

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 602
def reset_isolation_level
end

reset_sequence!(table, column, sequence = nil)

Set the sequence to the max value of the table’s column.

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 633
def reset_sequence!(table, column, sequence = nil)
  # Do nothing by default. Implement for PostgreSQL, Oracle, ...
end

restart_db_transaction()

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 618
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.

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 610
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)

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 624
def rollback_to_savepoint(name = nil)
  exec_rollback_to_savepoint(name)
end

select_all(arel, name = nil, binds = [], preparable: nil, async: false, allow_retry: false)

Returns an ActiveRecord::Result instance.

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 77
def select_all(arel, name = nil, binds = [], preparable: nil, async: false, allow_retry: false)
  arel = arel_from_relation(arel)
  intent = QueryIntent.new(
    adapter: self,
    arel: arel,
    name: name,
    binds: binds,
    prepare: prepared_statements && preparable,
    allow_async: async,
    allow_retry: allow_retry
  )

  intent.execute!

  if async
    intent.future_result
  else
    intent.cast_result
  end
end

select_one(arel, name = nil, binds = [], async: false)

Returns a record hash with the column names as keys and column values as values.

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 100
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.

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 117
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

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 105
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]

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 111
def select_values(arel, name = nil, binds = [])
  select_rows(arel, name, binds).map(&:first)
end

to_sql(arel_or_sql, binds = nil)

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 11
      def to_sql(arel_or_sql, binds = nil)
        unless binds.nil?
          ActiveRecord.deprecator.warn(<<~MSG)
            Passing `binds` to `to_sql` is deprecated and will be removed in Rails 9.0.
            The `binds` argument has been unused since bind parameters were moved into
            the Arel AST in Rails 5.2.
          MSG
        end
        sql, _ = to_sql_and_binds(arel_or_sql)
        sql
      end

transaction(requires_new: nil, isolation: nil, &block)

Runs the given block in a database transaction, and returns the result of the block.

Transaction callbacks ↑

transaction yields an ActiveRecord::Transaction object on which it is possible to register callback:

ActiveRecord::Base.transaction do |transaction|
  transaction.before_commit { puts "before commit!" }
  transaction.after_commit { puts "after commit!" }
  transaction.after_rollback { puts "after rollback!" }
end

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.lease_connection.transaction do  # BEGIN
  Model.lease_connection.transaction(requires_new: true) do  # CREATE SAVEPOINT active_record_1
    Model.lease_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.

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 495
def transaction(requires_new: nil, isolation: nil, joinable: true, &block)
  # If we're running inside the single, non-joinable transaction that
  # ActiveRecord::TestFixtures starts around each example (depth == 1),
  # an `isolation:` hint must be validated then ignored so that the
  # adapter isn't asked to change the isolation level mid-transaction.
  isolation_override = false
  if isolation && open_transactions == 1 && !current_transaction.joinable?
    iso = isolation.to_sym

    unless transaction_isolation_levels.include?(iso)
      raise ActiveRecord::TransactionIsolationError,
            "invalid transaction isolation level: #{iso.inspect}"
    end

    isolation_override = true
    old_isolation = current_transaction.isolation
    current_transaction.isolation = iso
    isolation = nil
  end

  if !requires_new && current_transaction.joinable?
    if isolation && current_transaction.isolation != isolation
      raise ActiveRecord::TransactionIsolationError, "cannot set isolation when joining a transaction"
    end
    yield current_transaction.user_transaction
  else
    within_new_transaction(isolation: isolation, joinable: joinable, &block)
  end
rescue ActiveRecord::Rollback
  # rollbacks are silently swallowed
ensure
  current_transaction.isolation = old_isolation if isolation_override
end

transaction_isolation_levels()

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 585
def transaction_isolation_levels
  TRANSACTION_ISOLATION_LEVELS
end

transaction_open?()

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 536
def transaction_open?
  current_transaction.open?
end

truncate(table_name, name = nil)

Executes the truncate statement.

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 361
def truncate(table_name, name = nil)
  execute(build_truncate_statement(table_name), name)
end

update(arel_or_sql, name = nil, binds = [])

Executes the update statement and returns the number of rows affected.

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 312
      def update(arel_or_sql, name = nil, binds = [])
        if binds.any?
          ActiveRecord.deprecator.warn(<<~MSG.squish)
            Passing `binds` as a positional argument to `update` is
            deprecated and will be removed in Rails 9.0. Use
            `Arel.sql(sql_with_placeholders, *binds)` to carry bind values
            inside the arel node instead —
            `update(sql, name, binds)` becomes
            `update(Arel.sql(sql, *binds), name)`.
          MSG
        end

        intent = QueryIntent.new(adapter: self, arel: arel_or_sql, name: name, binds: binds)

        intent.execute!
        intent.affected_rows
      end

write_query?(sql)

Determines whether the SQL statement is a write query.

Source: show | on GitHub 

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 150
def write_query?(sql)
  raise NotImplementedError
end