Naming discussion around blob v2

[Xuanwo]

Minor naming change. I think (but may be understanding wrong) that "blob version 1" is "inline only" and "blob version 2" is "inline, packed, and dedicated".

If this is correct then I think we should call it BLOBFILE_DESC_FIELD (or PACKED_DESC_FIELD). We are not replacing the existing inline approach, we are adding a new packed approach which will utilize blob-files. The inline approach will still use the 2-field description. The packed approach will use the 5-field description.

Originally posted by @westonpace in #4948 (review)

[Xuanwo]

cc @westonpace

My current idea is to have a blob v2 concept that includes all supported blob types like 'inline', 'packed', or 'dedicated'. This means blob v2 will cover all the uses of blob v1, which is just inline. I think this makes compatibility easier without changing any logic on the inline side.

We’ll only reuse the file encoding from blob v1 (inline), but all the table schema will be in blob v2. With this change, we can do the version check early at the table level instead of at the time of writing data.

Btw, I’m not strong on this. If you prefer to just keep packed/dedicated blob types as an extension to inline, I’m fine with making this change.

[westonpace]

I think we need a table level setting which controls whether we use blob files or not. If this is enabled then users don't have to select which columns are blobs. In other words, if we are doing table blobs, we shouldn't require the user to specify field metadata.

The field metadata for inline blobs can either stick around or be silently deprecated.

I'm not sure if this all makes sense.

[Xuanwo]

I think we need a table level setting which controls whether we use blob files or not. If this is enabled then users don't have to select which columns are blobs. In other words, if we are doing table blobs, we shouldn't require the user to specify field metadata.

The field metadata for inline blobs can either stick around or be silently deprecated.

I'm not sure if this all makes sense.

Yep, that's exactly what I want. The current implementation is a hard switch: once users are on file format 2.2, they must use blob v2. Now I understand what you mean: we can just add a table setting for blob v2 instead of tying it to file format 2.2.

I will implement this change later.