Access to primitive value from streaming SQL

I have a topic which has a value type of String which I am trying to use in a Lenses SQL processor, but I don’t seem to have access to the _value property like I do in SQL studio. Is the value available by some other means?

Not in the SQL processors, you just reference the field directly. You also have access to the key via _key. If the format of the data is a string you can then use the string functions to manipulate the data into fields.

No access to _metadata. yet. This will come in a future release.

And to further clarify, for one of the sql experts

You can use topicName._value to reference the whole value facet.
You should then be able to use the JSON_EXTRACT_FIRST function to achieve your goal. You can do something like json_extract_first(topic._value, "xpath")
Documentation are here: Functions | Documentation
Example here: Kafka streaming SQL with JSON strings | Help Center (edited)