Namespace

Class

Methods

Class Public methods

new()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 6
      def initialize
        super
        reset_transaction
      end
🔎 See on GitHub

Instance Public methods

add_transaction_record(record)

Register a record with the current transaction so that its after_commit and after_rollback callbacks can be called.

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 287
      def add_transaction_record(record)
        current_transaction.add_record(record)
      end
🔎 See on GitHub

begin_db_transaction()

Begins the transaction (and turns off auto-committing).

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 296
      def begin_db_transaction()    end
🔎 See on GitHub

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 code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 310
      def begin_isolated_db_transaction(isolation)
        raise ActiveRecord::TransactionIsolationError, "adapter does not support setting transaction isolation"
      end
🔎 See on GitHub

commit_db_transaction()

Commits the transaction (and turns on auto-committing).

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 315
      def commit_db_transaction()   end
🔎 See on GitHub

create(arel, name = nil, pk = nil, id_value = nil, sequence_name = nil, binds = [])

Alias for: insert

default_sequence_name(table, column)

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 329
      def default_sequence_name(table, column)
        nil
      end
🔎 See on GitHub

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

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

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 174
      def delete(arel, name = nil, binds = [])
        sql, binds = to_sql_and_binds(arel, binds)
        exec_delete(sql, name, binds)
      end
🔎 See on GitHub

empty_insert_statement_value()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 401
      def empty_insert_statement_value
        "DEFAULT VALUES"
      end
🔎 See on GitHub

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 code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 136
      def exec_delete(sql, name = nil, binds = [])
        exec_query(sql, name, binds)
      end
🔎 See on GitHub

exec_insert(sql, name = nil, binds = [], pk = nil, sequence_name = 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.

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 128
      def exec_insert(sql, name = nil, binds = [], pk = nil, sequence_name = nil)
        sql, binds = sql_for_insert(sql, pk, nil, sequence_name, binds)
        exec_query(sql, name, binds)
      end
🔎 See on GitHub

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.

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 121
      def exec_query(sql, name = "SQL", binds = [], prepare: false)
        raise NotImplementedError
      end
🔎 See on GitHub

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 code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 148
      def exec_update(sql, name = nil, binds = [])
        exec_query(sql, name, binds)
      end
🔎 See on GitHub

execute(sql, name = nil)

Executes the SQL statement in the context of this connection and returns the raw result from the connection adapter. Note: depending on your database connector, the result returned by this method may be manually memory managed. Consider using the exec_query wrapper instead.

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 114
      def execute(sql, name = nil)
        raise NotImplementedError
      end
🔎 See on GitHub

insert(arel, name = nil, pk = nil, id_value = nil, sequence_name = nil, binds = [])

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.

Also aliased as: create
📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 160
      def insert(arel, name = nil, pk = nil, id_value = nil, sequence_name = nil, binds = [])
        sql, binds = to_sql_and_binds(arel, binds)
        value = exec_insert(sql, name, binds, pk, sequence_name)
        id_value || last_inserted_id(value)
      end
🔎 See on GitHub

insert_fixture(fixture, table_name)

Inserts the given fixture into the table. Overridden in adapters that require something beyond a simple insert (eg. Oracle). Most of adapters should implement `insert_fixtures` that leverages bulk SQL insert. We keep this method to provide fallback for databases like sqlite that do not support bulk inserts.

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 343
      def insert_fixture(fixture, table_name)
        fixture = fixture.stringify_keys

        columns = schema_cache.columns_hash(table_name)
        binds = fixture.map do |name, value|
          if column = columns[name]
            type = lookup_cast_type_from_column(column)
            Relation::QueryAttribute.new(name, value, type)
          else
            raise Fixture::FixtureError, %(table "#{table_name}" has no column named #{name.inspect}.)
          end
        end

        table = Arel::Table.new(table_name)

        values = binds.map do |bind|
          value = with_yaml_fallback(bind.value_for_database)
          [table[bind.name], value]
        end

        manager = Arel::InsertManager.new
        manager.into(table)
        manager.insert(values)
        execute manager.to_sql, "Fixture Insert"
      end
🔎 See on GitHub

insert_fixtures(fixtures, table_name)

Inserts a set of fixtures into the table. Overridden in adapters that require something beyond a simple insert (eg. Oracle).

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 371
      def insert_fixtures(fixtures, table_name)
        ActiveSupport::Deprecation.warn(<<-MSG.squish)
          `insert_fixtures` is deprecated and will be removed in the next version of Rails.
          Consider using `insert_fixtures_set` for performance improvement.
        MSG
        return if fixtures.empty?

        execute(build_fixture_sql(fixtures, table_name), "Fixtures Insert")
      end
🔎 See on GitHub

insert_fixtures_set(fixture_set, tables_to_delete = [])

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 381
      def insert_fixtures_set(fixture_set, tables_to_delete = [])
        fixture_inserts = fixture_set.map do |table_name, fixtures|
          next if fixtures.empty?

          build_fixture_sql(fixtures, table_name)
        end.compact

        table_deletes = tables_to_delete.map { |table| "DELETE FROM #{quote_table_name table}".dup }
        total_sql = Array.wrap(combine_multi_statements(table_deletes + fixture_inserts))

        disable_referential_integrity do
          transaction(requires_new: true) do
            total_sql.each do |sql|
              execute sql, "Fixtures Load"
              yield if block_given?
            end
          end
        end
      end
🔎 See on GitHub

reset_sequence!(table, column, sequence = nil)

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

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 334
      def reset_sequence!(table, column, sequence = nil)
        # Do nothing by default. Implement for PostgreSQL, Oracle, ...
      end
🔎 See on GitHub

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 code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 319
      def rollback_db_transaction
        exec_rollback_db_transaction
      end
🔎 See on GitHub

rollback_to_savepoint(name = nil)

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 325
      def rollback_to_savepoint(name = nil)
        exec_rollback_to_savepoint(name)
      end
🔎 See on GitHub

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.

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 411
      def sanitize_limit(limit)
        if limit.is_a?(Integer) || limit.is_a?(Arel::Nodes::SqlLiteral)
          limit
        else
          Integer(limit)
        end
      end
🔎 See on GitHub

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

Returns an ActiveRecord::Result instance.

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 59
      def select_all(arel, name = nil, binds = [], preparable: nil)
        arel = arel_from_relation(arel)
        sql, binds = to_sql_and_binds(arel, binds)

        if preparable.nil?
          preparable = prepared_statements ? visitor.preparable : false
        end

        if prepared_statements && preparable
          select_prepared(sql, name, binds)
        else
          select(sql, name, binds)
        end
      end
🔎 See on GitHub

select_one(arel, name = nil, binds = [])

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

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 76
      def select_one(arel, name = nil, binds = [])
        select_all(arel, name, binds).first
      end
🔎 See on GitHub

select_rows(arel, name = nil, binds = [])

Returns an array of arrays containing the field values. Order is the same as that returned by columns.

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 93
      def select_rows(arel, name = nil, binds = [])
        select_all(arel, name, binds).rows
      end
🔎 See on GitHub

select_value(arel, name = nil, binds = [])

Returns a single value from a record

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 81
      def select_value(arel, name = nil, binds = [])
        single_value_from_rows(select_rows(arel, name, binds))
      end
🔎 See on GitHub

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 code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 87
      def select_values(arel, name = nil, binds = [])
        select_rows(arel, name, binds).map(&:first)
      end
🔎 See on GitHub

to_sql(arel_or_sql_string, binds = [])

Converts an arel AST to SQL

📝 Source code 
# 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
🔎 See on GitHub

transaction(requires_new: nil, isolation: nil, joinable: true)

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

Nested transactions support

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/5.7/en/savepoint.html Savepoints are supported by MySQL and PostgreSQL. SQLite3 version >= '3.6.8' supports savepoints.

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.

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 and postgresql adapters support setting the transaction isolation level.

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 260
      def transaction(requires_new: nil, isolation: nil, joinable: true)
        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) { yield }
        end
      rescue ActiveRecord::Rollback
        # rollbacks are silently swallowed
      end
🔎 See on GitHub

transaction_isolation_levels()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 298
      def transaction_isolation_levels
        {
          read_uncommitted: "READ UNCOMMITTED",
          read_committed:   "READ COMMITTED",
          repeatable_read:  "REPEATABLE READ",
          serializable:     "SERIALIZABLE"
        }
      end
🔎 See on GitHub

transaction_open?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 277
      def transaction_open?
        current_transaction.open?
      end
🔎 See on GitHub

transaction_state()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 291
      def transaction_state
        current_transaction.state
      end
🔎 See on GitHub

truncate(table_name, name = nil)

Executes the truncate statement.

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 141
      def truncate(table_name, name = nil)
        raise NotImplementedError
      end
🔎 See on GitHub

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

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

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 168
      def update(arel, name = nil, binds = [])
        sql, binds = to_sql_and_binds(arel, binds)
        exec_update(sql, name, binds)
      end
🔎 See on GitHub