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trie/trie.go improve the delete performance #22960

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Evolution404 wants to merge 1 commit into from
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trie/trie.go improve the delete performance #22960

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18 changes: 11 additions & 7 deletions trie/trie.go
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Original file line number Diff line number Diff line change
Expand Up @@ -415,13 +415,17 @@ func (t *Trie) delete(n node, prefix, key []byte) (bool, node, error) {
// value that is left in n or -2 if n contains at least two
// values.
pos := -1
for i, cld := range &n.Children {
if cld != nil {
if pos == -1 {
pos = i
} else {
pos = -2
break
if nn != nil {
pos = -2
} else {
Comment on lines +418 to +420
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@holiman holiman May 31, 2021

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I find this hard to intuitively verify. I think it might be easier to follow if you break here, so replace this with

if nn != nil{	
	// n still contains at least two values and cannot be reduced.
	return true, n, nil
}

As far as I can tell, that^ change should be equivalent with your change. However, looking at it, I still don't see why this is necessarily true/correct?

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@Evolution404 Evolution404 May 31, 2021

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if nn != nil, nn must be a child of n, which means that n itself doesn't need to be removed.

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@Evolution404 Evolution404 May 31, 2021

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And before the deletion, there must be another child of n.

for i, cld := range &n.Children {
if cld != nil {
if pos == -1 {
pos = i
} else {
pos = -2
break
}
}
}
}
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