Retrying immediately looked like eight chances and was one: a walk that bails
at the epoch check costs almost nothing, so all eight fit inside the single
compaction they were all losing to, and the listing refused having waited for
nothing. A quarter of a millisecond between attempts -- the agent's break-loop
idiom, legal here because the waiter is the listener thread and never the game
loop -- bounds the whole refusal at two milliseconds. Measured with a writer
noting and freeing on top of three thousand live blocks: 8 right answers in 200
without the pause, 200 in 200 with it. It is not magic, and the comment says
so: a writer that spends most of its time rearranging the table still gets
refused, which is the honest answer and used to be a zero-row lie.
The two cases the last commit left unwired are wired now, and a third joins
them: a listing taken while the table really is being compacted, which nothing
covered -- the full-of-live case never compacts and the churn case is
single-threaded, so the retry itself was exercised by nothing. It asserts only
what a slower machine cannot change: never zero rows, never a count that is
neither right nor a refusal. How the rest divides is printed, not pinned.
Joseph Ferano
739b871ff1