Need updates to proto ? when and online_enabled not serialized in from_proto.

Also, modify __eq__() and __copy__() for consider these new attributes ?

So why batch on read/write forces online to be true?
I think we need to think about if we really need a new tranform_when config. And if we need it, what is its relation with online/offline.
I think it might be counterintuitive that if this featureview is only used by batch or stream or on demand. what if the user defines it today as one mode and wants to change it to another one or allow both mode in the future?
My personal pint of view is removing any config for this. As long as you define the transformation, it will be applied to run before writing to destination. Use online/offline to control the destination only, if both are off, then no write. For any transformation needed on read, this should be configured at API level. Fo example, you can put get_online_feature(transform=true) to force transformation.

I think we need to think about if we really need a new tranform_when config. And if we need it, what is its relation with online/offline.

Here's how things actually work:

1. Batch

• Sometimes data can be transformed online
  1. On Reads
  2. On Writes
• Sometimes not, and that's basically a batch transform with no feature server transformation and pure materialization

2. Streaming

• Handles historical data the same way it handles online serving

that's really what the transform_when indicates.

We need something other than online because the rest will be executed by the server and you can't orchestrate the transformation on write during retrieval.

I'm fine with renaming something but we need something equivalent to write_to_online_store that's more obvious.

online = true means write to online store.

transform_on_write should be removed from the server. it's a hacky way. #5283. this PR doesn't get enough reviews I think.
#5300. I think this one is also not ideal implementation as well.

When you use get_online_feature, you should assign it a transform=true to run transformation in "retrieval".

I've read through the feature server code and on demand feature view implementation. I think a lot code needs to be refactored. And if you think there is some lines of code won't work you can tag me. I'll try to explain it

Yes we agreed on this direction and I'm going to implement things that way. Just need to finish the work.