TransactionsAndSavepoints

Transaction

Clear offer simple transaction system. The methods are Clear::SQL.transaction and Clear::SQL.rollback.

During transaction, if any errors occurs or you manually call Clear::SQL.rollback, Clear will throw a ROLLBACK.

Note than Clear::SQL.rollback will not raise any errors, but the code after the rollback will never be executed.

Clear::SQL.transaction do
  ## Do something

  Clear::SQL.rollback if something_wrong_happeneds
end

You can check whether you're in transaction at a specific moment by calling Clear::SQL.in_transaction?

Savepoints

Transactions cannot be nested. This code will do exactly the same:

Clear::SQL.transaction do
  Clear::SQL.rollback
  do_something
end

Clear::SQL.transaction do
  Clear::SQL.transaction do
    Clear::SQL.rollback
  end

  do_something
end

In both case, do_something will never be called.

That's where savepoint comes in:

Clear::SQL.with_savepoint do
  Clear::SQL.rollback
  do_something
end

Clear::SQL.with_savepoint do
  Clear::SQL.with_savepoint do
    Clear::SQL.rollback
  end

  do_something
end

In this case, the second example will call do_something.

Savepoints can be nested and live into a transaction. Use them wisely !