filtered streaming fix

[Sanhaoji2]

• Does this PR have a descriptive title that could go in our release notes?
• Does this PR add any new dependencies?
• Does this PR modify any existing APIs?
  • Is the change to the API backwards compatible?
• Should this result in any changes to our documentation, either updating existing docs or adding new ones?

Reference Issues/PRs

What does this implement/fix? Briefly explain your changes.

Any other comments?

[rakri]

So the main logical change in this PR, is that we get rid of frozen point concept, but medoids (global or for any label) can never be deleted? Meaning that we need to skip outputting them at search time, if they are deleted..

[rakri]

So now location_to_tag and tag_to_location will not contain these medoids once they are deleted.. Are we making sure that some other new inserted node doesnt take up these locations and get inserted there? In other words, we now lose the invariant delete_set.size() + location_to_tag.size() + empty_slots = _max_points?

[Sanhaoji2]

the medoids are not moving to delete set, so it won't be assigned to other nodes again in insert operation.

For the question "Meaning that we need to skip outputting them at search time, if they are deleted", yes, they may skip outputting if they got deleted, the logic is as the same as using frozen points:

In previous logic we start with frozen points, while the frozen points are selected in searching, we also need to skip them, there are no different here.

For the question "lose the invariant delete_set.size() + location_to_tag.size() + empty_slots = _max_points", yes.