Struct ReverseRangeIter 

pub struct ReverseRangeIter<'p> { /* private fields */ }

A descending range cursor. Unlike reversing a forward RangeIter, this pins one leaf at a time and never materialises the range it is walking.

Implementations

impl ReverseRangeIter<'_>

pub fn peek_ref(&mut self) -> Result<Option<(&[u8], &[u8])>>

The descending record the cursor is parked on, borrowed from the pinned leaf, with no allocation. Paired with ReverseRangeIter::step this is the PULL cursor the forward iterator already has: peek, use, step, peek.

A query executor cannot live inside for_each_ref’s callback – it has to interleave the walk with a heap, a work meter and a cancellation check – and until this existed, every descending order had to materialise its whole range before it could rank it. Same leaf pin, same tree-id and cycle checks, same overflow resolution as the callback form.

pub fn step(&mut self)

Step past the record the last peek returned. Crossing into the leaf to the LEFT is left to the next peek, which retreats through the saved parent path when the slot index reaches the start of the leaf.

pub fn for_each_ref(self, f: impl FnMut(&[u8], &[u8]) -> bool) -> Result<()>

Visit descending records as borrows into one pinned leaf. The cursor is bounded by the buffer pool; a caller stopping after k entries pays for only the pages containing those entries.