perf: skip dedup map in getChildrenNodes#570
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getChildrenNodes went through mapNodes, which builds a
map[*html.Node]bool to deduplicate results merged across source nodes.
That dedup is pointless in this case: every child has exactly one parent, so
the children of distinct (already-unique) source nodes form disjoint sets and
can never collide. Walk the sources directly into the result instead, keeping a
single-node fast path that returns the child slice without an extra copy.
This mirrors the disjoint-set reasoning already applied to the parent
traversal helpers.
benchstat -count=10:
sec/op B/op allocs/op
Contents-8 -55.52% -67.63% -19.23%
ContentsFiltered-8 -15.25% -33.61% -9.68%
ChildrenFiltered-8 -32.84% -3.23% -7.69%
Children-8 ~ (single-node fast path unchanged)
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getChildrenNodes went through mapNodes, which builds a map[*html.Node]bool to deduplicate results merged across source nodes. That dedup is pointless in this case: every child has exactly one parent, so the children of distinct (already-unique) source nodes form disjoint sets and can never collide. Walk the sources directly into the result instead, keeping a single-node fast path that returns the child slice without an extra copy.
This mirrors the disjoint-set reasoning already applied to the parent traversal helpers.
benchstat -count=10:
Contents-8 -55.52% -67.63% -19.23%
ContentsFiltered-8 -15.25% -33.61% -9.68%
ChildrenFiltered-8 -32.84% -3.23% -7.69%
Children-8 ~ (single-node fast path unchanged)