Filterable changefeed, max changefeeds

Hi, congratulations on the changefeed functionality!

Apologies in advance if I missed existing docs/responses on this subject - I am curious if there are any plans to support a SELECT filter for a changefeed?

Right now it seems that the only way to limit what is emitted by a changefeed is to point it at a certain table - it would be really great if it was possible to apply a filter on a per changefeed basis.

Another, semi-related question: is there a limit to the number of changefeeds that can be active on a cluster? I assume qps on the cluster will have some effect on this but am looking for “best practice” advice.

Thank you very much!