According to this link
The problem is going to be that the experimental.join() function forces you to join on _time.
My current use does not join on _time. It joins on a custom field. In fact it’s critical that I don’t join on _time for what I’m doing.
What am I doing? I’m adding a product code to a table of timed data. The product code links _field with a _code. But the table with the _code value has 0 as the time because it covers all-time.
So please please either add the same flexibility to the experimental.join() function. Or commit to keeping both permanently.