MySQL / MariaDB window function support

[andypohl]

I'm running into the same problem this person ran into and reported on the RMariaDB repository.

Before you ask me to go to the RStudio community site and whine there, I'll just mention I did that, and I've been politely encouraged by an authority there to post an issue here.

That post has my non-reprex example illustrating my confirmation of the conclusion by @krlmlr that it's dbplyr that's missing the necessary piece of the puzzle. It's certainly a similar issue to #144 but in this case, I think the DBI part is working. But anyhow since that issue hasn't been closed, I thought maybe there's perhaps interest in adding window function querying functionality to MariaDB/MySQL too.

[hadley]

https://mariadb.com/kb/en/library/window-functions/