This depends on #25093. Once the internal last cache has been set up and implements Datafusion's TableProvider, we can create the User-Defined Table Function (UDTF) implementation using Datafusion's TableFunctionImpl trait.

The API for this function should look like so:

last_cache(table_name, [cache_name])

• table_name: the table in the database that has the last cache
• cache_name (optional): if there are multiple last caches for a table, the name of the last cache must be passed

So, its usage would look like so

SELECT * FROM last_cache('cpu')
SELECT time, usage FROM last_cache('cpu', 'cpu_usage_cache')

The last cache can be combined with predicates to operate on keys used in the last cache:

SELECT * FROM last_cache('mem') WHERE host = 'us-east'

Getting this to work may require some upstream changes to influxdb3_core to extend the IOxSessionContext with the UDTF.