[cormacrelf]

There could also be a “clean the slate” streaming directive, which means “I started the query again, please scratch what got delivered already”.

[JelteF]

That effictively means the client cannot actually start processing the results before everything is received. Because you would have to undo everything you did with the data you received before. So basically this would simply be a non streaming version.

[Bootvis]

I believe the best you can do is to delay streaming. Now you have the problem of deciding when to start...