use path to append data

[xiongjiwei]

for now WriteAppend needs the object which will append to, is it possible to use the path? something like

WriteAppend(path string, r io.Reader, size int64, pairs ...Pair) (n int64, err error)

[Xuanwo]

For most storage services, WriteAppend needs append-offset so our API requires o *Object. To allow our code to run on all storage platforms, it's unlikely to use path only.

[JinnyYi]

• For object storage like oss, an appendable object is readable, users can perform the AppendObject operation to create an appendable object or append data to an existing object. So use path to append data may seem reasonable at first glance, but users should maintain the append-offset.
• Service like dropbox needs a start operation to start an append process and a finish operation to mark this appends process has been finished. And before the finish has been called, the object is not readable for user. If use path to append data, users have to upload all the data at once and cannot append anymore.

So for go-storage, Appender is not a single operation like WriteAppend and we use Object to maintain some information for the append object. Ref:

• Appender Introduction
• GSP-44: Add CommitAppend in Appender

[Xuanwo]

Closed for no more comments. Please feel free to reopen it!