I think Brian did partially implement ADQL in albuquery before we abandoned that line of work. I imagine we can tell from the history when this was done, if that's what necessary to resolve this epic.

Added Fritz Mueller as a watcher to help us sort this out.

Albuquery/dbserv are no more, per Gregory's comment.  Qserv meanwhile has been extended to deduce basic geometric extensions from usage of scisql UDFs for the most common point-in-circle and point-in-polygon cases, and Rubin's TAP service implementation currently generates queries of this type when backed by Qserv.

I would recommend that we close "research" ticket DM-14535 as done, given that Brian did do some research (documented on ticket), and then we close this epic.

If support for additional types of ADQL queries is desired, we can open new tickets containing actual specifics ( ! ) and example queries, then divide necessary work between the teams currently responsible for the TAP service and Qserv parts.

I see the description of the epic is "define and document...", however.  There is a Qserv documentation sprint currently underway, and this will include definition of geometric queries supported by Qserv.  I am not sure where/how the upstream ADQL support boundaries are delineated in documentation, though?

We do have some ADQL but not complete. I think this can close based on the age and content. Fritz has work on the back end of it.