I have a question about a behavioral difference in InvalidatePossiblyObsoleteSlot() between PG15 (and earlier) and PG16 (and later):
In PG15 and earlier: while attempting to acquire a slot, if the slot's restart_lsn advanced to be greater than oldestLSN during the process, the slot would not be marked invalid.
In PG16 and later: the invalidation decision is made solely based on the initial_restart_lsn captured at the start of the check, even if the slot's restart_lsn advances above oldestLSN during the process, the slot may still be marked invalid.
I wonder why not decide whether to mark the slot as invalid based on the slot's current restart_lsn? If a slot's restart_lsn has already advanced sufficiently during the invalidation process, indicating it's actively being used, shouldn't we refrain from invalidating it? What is the rationale behind this design change?
