Misleading comment in prologue of ReorderBufferQueueMessage

The name of the function suggests that the given message will be queued in
ReorderBuffer. The prologue of the function says so too
776 /*
777 * Queue message into a transaction so it can be processed upon commit.
778 */
It led me to think that a non-transactional message is processed along with
the surrounding transaction, esp. when it has an associated xid.

But in reality, the function queues only a transactional message and
decoders a non-transactional message immediately without waiting for a
commit.

We should modify the prologue to say
"Queue a transactional message into a transaction so that it can be
processed upon commit. A non-transactional message is processed
immediately." and also change the name of the function
to ReorderBufferProcessMessage(), but the later may break API compatibility.

--
Best Wishes,
Ashutosh