feat: a new userData API Remove

[tylitianrui]

issue
a new API for deleting a key instead of setting nil.

• a key is removed logically . adding a new attribute status to userDataKV which report whether the userDataKV is deleted or not.
• the memory of the deleted one will be reuse,

[erikdubbelboer]

Why ʼstatusDeletedʼ why not just remove the entry from the slice?

[tylitianrui]

Why ʼstatusDeletedʼ why not just remove the entry from the slice?

removing an entry from the slice will migrate other entries following the removed one forward . it causes memory migration. removing an entry logically can avoiding the migration.

[erikdubbelboer]

I'm not sure what you mean with memory migration but rearranging the slice isn't a bad thing you can just copy the last entry of the slice to the one that gets deleted and decrease the len by 1. Just make sure to set the value of that last entry to nil before you decrease the length so the GC doen't keep it alive.

[erikdubbelboer]

So here something like:

n--
args[i] = args[n]
args[n].value = nil // Make sure not to keep the value alive for the GC.
args = args[:n]
*d = args

[tylitianrui]

thanks for reviewing, i will change it.

[erikdubbelboer]

Thanks!