[Proposal]: Deprecate the collection option in list backup

[huanghaoyuanhhy]

Background

The collection option in the list backup command was originally introduced to filter the returned backup list so that only backups containing the specified collection would be displayed.

However, this feature was implemented before Milvus introduced multi-DB support, and it has never supported specifying a database name. Over time, we’ve noticed that no users have reported issues or requested improvements related to this option, which suggests that it is rarely (if ever) used.

Problem

To implement this option, the current code must fully read and parse the entire backup metadata in order to determine which backups contain the specified collection.
This process is inefficient and introduces unnecessary performance overhead.
Additionally, maintaining and testing this option adds extra development complexity and cost without clear user benefits.

Migration Plan

Starting from the next release:

• Requests using the collection option in list backup will return an error.
• After a deprecation period, the option will be completely removed.