What does beginTransaction returning null mean?

[tyteen4a03]

When I want to start a transaction, I expect beginTransaction() to start the transaction, or fail. But it is possible for its return value to be null. Subsequent usages of e.g. rollbackTransaction() does not take null as a value, and the example code uses if transactionId checks.

What does a null transaction ID mean? If I receive null for a transaction ID, should I early-abort?

[denolfe]

The base database adapter returns null for transactionIDs to indicate that transactions are not supported or not enabled.

Are you passing any additional options to your database adapter?

[tyteen4a03]

The base database adapter returns null for transactionIDs to indicate that transactions are not supported or not enabled.

I think this should not be hidden from the developer and instead should throw an exception. From reading the types it's not clear why the transaction ID can be null.

Are you passing any additional options to your database adapter?

I'm not.