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Improve Iterator Performance of Seeking with Prefix #1719

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Improve Iterator Performance of Seeking with Prefix #1719

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7b56978
improve iterator performance of seeking with prefix
zzyalbert Jul 2, 2021
2ec98c3
fix typo
zzyalbert Jul 19, 2021
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14 changes: 12 additions & 2 deletions iterator.go
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Expand Up @@ -591,7 +591,8 @@ func (it *Iterator) Next() {

// Set next item to current
it.item = it.data.pop()
for it.iitr.Valid() {
// escape when current key doesn't have prefix
for it.iitr.Valid() && hasPrefix(it.iitr, it.opt.Prefix) {
if it.parseItem() {
// parseItem calls one extra next.
// This is used to deal with the complexity of reverse iteration.
Expand Down Expand Up @@ -739,7 +740,8 @@ func (it *Iterator) prefetch() {
i := it.iitr
var count int
it.item = nil
for i.Valid() {
// escape when current key doesn't have prefix
for i.Valid() && hasPrefix(i, it.opt.Prefix) {
if !it.parseItem() {
continue
}
Expand All @@ -750,6 +752,14 @@ func (it *Iterator) prefetch() {
}
}

// hasPrefix would check if current key in the internal iterator has the prefix
func hasPrefix(it y.Iterator, prefix []byte) bool {
if len(prefix) > 0 {
return bytes.HasPrefix(y.ParseKey(it.Key()), prefix)
}
return true
}

// Seek would seek to the provided key if present. If absent, it would seek to the next
// smallest key greater than the provided key if iterating in the forward direction.
// Behavior would be reversed if iterating backwards.
Expand Down