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added prev method to range iterator

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This commit is contained in:
Todd Gruben 2023-04-05 15:56:04 -05:00 • committed by pokeeffe-molecula
parent 12e00c7949
commit 1900ba1789
1 changed files with 26 additions and 0 deletions
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26
tstore/range.go
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@ -117,3 +117,29 @@ func (iter *RangeIterator) Next() bool {
iter.key, iter.item, iter.err = iter.tree.getTuple(iter.node, int(iter.cursor), iter.schema)
return iter.key.Less(iter.to) && iter.err == nil
}
// TODO(twg) 2023/04/05 untested just added while it was top of mind
func (iter *RangeIterator) Prev() bool {
if iter.done {
return false
}
iter.cursor--
if iter.cursor < 0 {
page := iter.node.page.ReadPrevPointer()
iter.node.releaseReadLatch()
iter.tree.unpin(iter.node)
if page.Page == bufferpool.INVALID_PAGE { // at the end
return false
}
n, err := iter.tree.fetchNode(page)
iter.err = err
if iter.err != nil {
return false
}
iter.node = n
iter.node.takeReadLatch()
iter.cursor = iter.node.slotCount() - 1
}
iter.key, iter.item, iter.err = iter.tree.getTuple(iter.node, int(iter.cursor), iter.schema)
return iter.from.Less(iter.key) && iter.err == nil
}