Introduce TermGroupFacetCollectorManager for concurrent grouped faceting#16292
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javanna wants to merge 3 commits into
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Introduce TermGroupFacetCollectorManager for concurrent grouped faceting#16292javanna wants to merge 3 commits into
javanna wants to merge 3 commits into
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The old TermGroupFacetCollector could not be adapted to CollectorManager: its cross-segment deduplication was fundamentally sequential. At doSetNextReader(), all previously seen (group, facet) pairs were re-looked up in each new segment's ordinal dictionary to rebuild the per-segment SentinelIntSet. That O(pairs × segments) walk cannot be split across concurrent slices, and every unique hit allocated a BytesRef copy in the collection hot path. The replacement design tracks (groupOrd, facetOrd) pairs as packed longs in a per-slice LongHashSet during collection — no BytesRef allocations in the hot path. Ordinals are translated to terms once per segment in LeafCollector.finish(), and reduce() performs global deduplication across all slices via a HashSet<GroupFacetPair>, correctly counting groups whose documents span multiple search slices. All 8 deprecated IndexSearcher#search(Query, Collector) call sites in TestGroupFacetCollector are removed as a result. TermGroupFacetCollector is now deprecated in favour of TermGroupFacetCollectorManager The base class GroupFacetCollector is also now deprecated. Relates to apache#12892.
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Jun 24, 2026
| * | ||
| * @lucene.experimental | ||
| */ | ||
| public class GroupedFacetResult { |
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This is temporarily duplicated: same code is also in within the now deprecated GroupFacetCollector. The idea is to backport this change cleanly to 10.x, then remove the deprecated classes from main.
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The old TermGroupFacetCollector could not be adapted to CollectorManager:
its cross-segment deduplication was fundamentally sequential. At
doSetNextReader(), all previously seen (group, facet) pairs were
re-looked up in each new segment's ordinal dictionary to rebuild the
per-segment SentinelIntSet. That O(pairs × segments) walk cannot be
split across concurrent slices, and every unique hit allocated a
BytesRef copy in the collection hot path.
The replacement design tracks (groupOrd, facetOrd) pairs as packed
longs in a per-slice LongHashSet during collection — no BytesRef
allocations in the hot path. Ordinals are translated to terms once per
segment in LeafCollector.finish(), and reduce() performs global
deduplication across all slices via a HashSet,
correctly counting groups whose documents span multiple search slices.
All 8 deprecated IndexSearcher#search(Query, Collector) call sites in
TestGroupFacetCollector are removed as a result.
TermGroupFacetCollector is now deprecated in favour of TermGroupFacetCollectorManager
The base class GroupFacetCollector is also now deprecated.
Relates to #12892.