feat(rag): hybrid multi-path search with RRF fusion

Add configurable hybrid mode on KnowledgeSearchPort that fuses dense unfiltered, dense filtered, and lexical ranks via RRF while preserving dense-compatible threshold scores. Archives Delivery 2 OpenSpec change.
2026-07-27 18:33:31 +08:00
parent ac1f831903
commit 376ad0c241
19 changed files with 661 additions and 8 deletions
@@ -3,12 +3,15 @@ package com.superbiz.agent.service;
 import com.superbiz.agent.dto.RetrievalTrace;
 import com.superbiz.agent.dto.RetrievedEvidenceCandidate;
 import com.superbiz.agent.service.retrieval.KnowledgeSearchHit;
+import com.superbiz.agent.service.retrieval.KnowledgeSearchMode;
 import com.superbiz.agent.service.retrieval.KnowledgeSearchPort;
 import com.superbiz.agent.service.retrieval.KnowledgeSearchRequest;
+import org.springframework.beans.factory.annotation.Value;
 import org.springframework.stereotype.Service;

 import java.util.ArrayList;
 import java.util.List;
+import java.util.Locale;

 /**
 * L1 向量检索适配器。
@@ -23,6 +26,9 @@ public class KnowledgeDocumentRetriever {

    private final KnowledgeSearchPort knowledgeSearchPort;

+    @Value("${retrieval.search.mode:dense}")
+    private String searchMode = "dense";
+
    public KnowledgeDocumentRetriever(KnowledgeSearchPort knowledgeSearchPort) {
        this.knowledgeSearchPort = knowledgeSearchPort;
    }
@@ -39,8 +45,11 @@ public class KnowledgeDocumentRetriever {
    public RetrievalAttemptResult retrieve(String attemptName, String query, String categoryFilter, int topK) {
        long start = System.currentTimeMillis();
        try {
+            KnowledgeSearchMode mode = "hybrid".equalsIgnoreCase(trim(searchMode))
+                    ? KnowledgeSearchMode.HYBRID
+                    : KnowledgeSearchMode.DENSE;
            List<KnowledgeSearchHit> hits = knowledgeSearchPort.search(
-                    KnowledgeSearchRequest.dense(query, topK, categoryFilter));
+                    new KnowledgeSearchRequest(query, topK, categoryFilter, mode));
            List<RetrievedEvidenceCandidate> candidates = toCandidates(attemptName, hits);
            return new RetrievalAttemptResult(
                    attempt(attemptName, query, categoryFilter, candidates.size(), null,
@@ -110,6 +119,10 @@ public class KnowledgeDocumentRetriever {
        return hits.get(0).score();
    }

+    private static String trim(String value) {
+        return value == null ? "" : value.trim().toLowerCase(Locale.ROOT);
+    }
+
    /**
     * 单次检索 attempt 的结果包。
     */
@@ -0,0 +1,73 @@
+package com.superbiz.agent.service.retrieval;
+
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Locale;
+import java.util.Set;
+
+/**
+ * Sparse-lite lexical ranking over already recalled candidates.
+ * Not a substitute for inverted-index BM25; expands ordering signal only.
+ */
+public final class LexicalRanker {
+
+    private LexicalRanker() {
+    }
+
+    public static List<KnowledgeSearchHit> rank(String query, List<KnowledgeSearchHit> candidates) {
+        if (candidates == null || candidates.isEmpty()) {
+            return List.of();
+        }
+        Set<String> terms = tokenize(query);
+        if (terms.isEmpty()) {
+            return List.copyOf(candidates);
+        }
+        List<ScoredHit> scored = new ArrayList<>(candidates.size());
+        for (KnowledgeSearchHit hit : candidates) {
+            String haystack = (nullToEmpty(hit.title()) + " "
+                    + nullToEmpty(hit.breadcrumb()) + " "
+                    + nullToEmpty(hit.content())).toLowerCase(Locale.ROOT);
+            int hits = 0;
+            for (String term : terms) {
+                if (haystack.contains(term)) {
+                    hits++;
+                }
+            }
+            double coverage = hits / (double) terms.size();
+            scored.add(new ScoredHit(hit, coverage, hits));
+        }
+        scored.sort(Comparator
+                .comparingDouble((ScoredHit s) -> s.coverage).reversed()
+                .thenComparingInt((ScoredHit s) -> s.hits).reversed()
+                .thenComparingInt(s -> s.hit.originalRank()));
+        return scored.stream().map(s -> s.hit).toList();
+    }
+
+    static Set<String> tokenize(String query) {
+        if (query == null || query.isBlank()) {
+            return Set.of();
+        }
+        String normalized = query.toLowerCase(Locale.ROOT);
+        String[] parts = normalized.split("[^\\p{IsAlphabetic}\\p{IsDigit}]+");
+        Set<String> terms = new LinkedHashSet<>();
+        for (String part : parts) {
+            if (part == null) {
+                continue;
+            }
+            String term = part.trim();
+            if (term.length() >= 2) {
+                terms.add(term);
+            }
+        }
+        return terms;
+    }
+
+    private static String nullToEmpty(String value) {
+        return value == null ? "" : value;
+    }
+
+    private record ScoredHit(KnowledgeSearchHit hit, double coverage, int hits) {
+    }
+}
@@ -0,0 +1,85 @@
+package com.superbiz.agent.service.retrieval;
+
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.function.Function;
+
+/**
+ * Reciprocal Rank Fusion helpers.
+ *
+ * <pre>
+ * RRF_w(d) = Σ w_i / (k + rank_i(d))
+ * </pre>
+ */
+public final class RrfFusion {
+
+    private RrfFusion() {
+    }
+
+    public static <T> List<Scored<T>> fuse(List<RankedPath<T>> paths,
+                                           int rrfK,
+                                           Function<T, String> identityFn) {
+        if (paths == null || paths.isEmpty()) {
+            return List.of();
+        }
+        int k = Math.max(1, rrfK);
+        Map<String, Acc<T>> acc = new LinkedHashMap<>();
+        for (RankedPath<T> path : paths) {
+            if (path == null || path.items() == null || path.items().isEmpty()) {
+                continue;
+            }
+            double weight = path.weight() <= 0 ? 1.0 : path.weight();
+            List<T> items = path.items();
+            for (int i = 0; i < items.size(); i++) {
+                T item = items.get(i);
+                if (item == null) {
+                    continue;
+                }
+                String id = identityFn.apply(item);
+                if (id == null || id.isBlank()) {
+                    continue;
+                }
+                int rank = i + 1;
+                double contrib = weight / (k + rank);
+                Acc<T> bucket = acc.computeIfAbsent(id, ignored -> new Acc<>(item));
+                bucket.score += contrib;
+                bucket.ranks.put(path.name(), rank);
+                // Prefer first-seen item payload; callers should put preferred path first if needed.
+            }
+        }
+        List<Scored<T>> scored = new ArrayList<>(acc.size());
+        for (Map.Entry<String, Acc<T>> entry : acc.entrySet()) {
+            Acc<T> value = entry.getValue();
+            scored.add(new Scored<>(entry.getKey(), value.item, value.score, Map.copyOf(value.ranks)));
+        }
+        scored.sort(Comparator
+                .comparingDouble((Scored<T> s) -> s.rrfScore()).reversed()
+                .thenComparing(Scored::identity));
+        return scored;
+    }
+
+    public record RankedPath<T>(String name, List<T> items, double weight) {
+        public RankedPath {
+            Objects.requireNonNull(name, "name");
+            items = items == null ? List.of() : List.copyOf(items);
+        }
+    }
+
+    public record Scored<T>(String identity, T item, double rrfScore, Map<String, Integer> ranks) {
+    }
+
+    private static final class Acc<T> {
+        private final T item;
+        private double score;
+        private final Map<String, Integer> ranks = new HashMap<>();
+
+        private Acc(T item) {
+            this.item = item;
+        }
+    }
+}
@@ -2,15 +2,22 @@ package com.superbiz.agent.service.retrieval;

 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.superbiz.agent.service.VectorSearchService;
+import org.springframework.beans.factory.annotation.Value;
 import org.springframework.stereotype.Component;

 import java.util.ArrayList;
 import java.util.LinkedHashMap;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;

 /**
- * Dense-only {@link KnowledgeSearchPort} backed by the existing vector search facade.
+ * {@link KnowledgeSearchPort} backed by the existing vector search facade.
+ *
+ * <ul>
+ *   <li>{@code DENSE}: single dense path (legacy behavior)</li>
+ *   <li>{@code HYBRID}: dense unfiltered + optional dense filtered + lexical rank, fused by RRF</li>
+ * </ul>
 */
@Component
 public class VectorKnowledgeSearchAdapter implements KnowledgeSearchPort {
@@ -18,6 +25,21 @@ public class VectorKnowledgeSearchAdapter implements KnowledgeSearchPort {
    private final VectorSearchService vectorSearchService;
    private final ObjectMapper objectMapper;

+    @Value("${retrieval.search.mode:dense}")
+    private String configuredMode = "dense";
+
+    @Value("${retrieval.hybrid.rrf-k:60}")
+    private int rrfK = 60;
+
+    @Value("${retrieval.hybrid.weight.dense-unfiltered:1.0}")
+    private double weightDenseUnfiltered = 1.0;
+
+    @Value("${retrieval.hybrid.weight.dense-filtered:1.0}")
+    private double weightDenseFiltered = 1.0;
+
+    @Value("${retrieval.hybrid.weight.lexical:1.0}")
+    private double weightLexical = 1.0;
+
    public VectorKnowledgeSearchAdapter(VectorSearchService vectorSearchService, ObjectMapper objectMapper) {
        this.vectorSearchService = vectorSearchService;
        this.objectMapper = objectMapper;
@@ -25,13 +47,101 @@ public class VectorKnowledgeSearchAdapter implements KnowledgeSearchPort {

    @Override
    public List<KnowledgeSearchHit> search(KnowledgeSearchRequest request) {
-        if (request.mode() == KnowledgeSearchMode.HYBRID) {
-            // Delivery 2 will implement true hybrid. Until then, fall back to dense.
+        KnowledgeSearchMode mode = resolveMode(request.mode());
+        if (mode == KnowledgeSearchMode.HYBRID) {
+            return searchHybrid(request);
        }
+        return searchDense(request.query(), request.topK(), request.categoryFilter());
+    }
+
+    private List<KnowledgeSearchHit> searchDense(String query, int topK, String categoryFilter) {
        List<VectorSearchService.SearchResult> results = vectorSearchService.searchSimilarDocuments(
-                request.query(),
-                request.topK(),
-                request.categoryFilter());
+                query, topK, categoryFilter);
+        return toHits(results);
+    }
+
+    private List<KnowledgeSearchHit> searchHybrid(KnowledgeSearchRequest request) {
+        String query = request.query();
+        int topK = request.topK();
+        String category = trimToNull(request.categoryFilter());
+
+        List<KnowledgeSearchHit> unfiltered = searchDense(query, topK, null);
+        List<KnowledgeSearchHit> filtered = category == null
+                ? List.of()
+                : searchDense(query, topK, category);
+
+        Map<String, KnowledgeSearchHit> unionByKey = new LinkedHashMap<>();
+        for (KnowledgeSearchHit hit : unfiltered) {
+            unionByKey.putIfAbsent(hit.evidenceKey(), hit);
+        }
+        for (KnowledgeSearchHit hit : filtered) {
+            unionByKey.putIfAbsent(hit.evidenceKey(), hit);
+        }
+        List<KnowledgeSearchHit> union = new ArrayList<>(unionByKey.values());
+        List<KnowledgeSearchHit> lexical = LexicalRanker.rank(query, union);
+
+        List<RrfFusion.RankedPath<KnowledgeSearchHit>> paths = new ArrayList<>();
+        paths.add(new RrfFusion.RankedPath<>("dense_unfiltered", unfiltered, weightDenseUnfiltered));
+        if (!filtered.isEmpty()) {
+            paths.add(new RrfFusion.RankedPath<>("dense_filtered", filtered, weightDenseFiltered));
+        }
+        if (!lexical.isEmpty()) {
+            paths.add(new RrfFusion.RankedPath<>("lexical", lexical, weightLexical));
+        }
+
+        List<RrfFusion.Scored<KnowledgeSearchHit>> fused = RrfFusion.fuse(
+                paths, rrfK, KnowledgeSearchHit::evidenceKey);
+
+        List<KnowledgeSearchHit> ordered = new ArrayList<>();
+        int rank = 1;
+        for (RrfFusion.Scored<KnowledgeSearchHit> scored : fused) {
+            if (ordered.size() >= topK) {
+                break;
+            }
+            KnowledgeSearchHit base = scored.item();
+            Map<String, String> metadata = new LinkedHashMap<>(
+                    base.metadata() == null ? Map.of() : base.metadata());
+            metadata.put("fusedScore", Double.toString(scored.rrfScore()));
+            metadata.put("fusionRanks", scored.ranks().toString());
+            metadata.put("fusionRank", Integer.toString(rank));
+            ordered.add(new KnowledgeSearchHit(
+                    base.id(),
+                    base.content(),
+                    base.score(),
+                    base.rawScore(),
+                    base.scoreLabel(),
+                    base.metadataJson(),
+                    metadata,
+                    base.docId(),
+                    base.chunkIndex(),
+                    base.evidenceKey(),
+                    base.source(),
+                    base.title(),
+                    base.breadcrumb(),
+                    rank
+            ));
+            rank++;
+        }
+        return ordered;
+    }
+
+    private KnowledgeSearchMode resolveMode(KnowledgeSearchMode requestMode) {
+        if (requestMode == KnowledgeSearchMode.HYBRID) {
+            return KnowledgeSearchMode.HYBRID;
+        }
+        if (requestMode == KnowledgeSearchMode.DENSE) {
+            // Allow global config to force hybrid even if caller passes DENSE default.
+            String configured = configuredMode == null ? "dense" : configuredMode.trim().toLowerCase(Locale.ROOT);
+            if ("hybrid".equals(configured)) {
+                return KnowledgeSearchMode.HYBRID;
+            }
+            return KnowledgeSearchMode.DENSE;
+        }
+        String configured = configuredMode == null ? "dense" : configuredMode.trim().toLowerCase(Locale.ROOT);
+        return "hybrid".equals(configured) ? KnowledgeSearchMode.HYBRID : KnowledgeSearchMode.DENSE;
+    }
+
+    private List<KnowledgeSearchHit> toHits(List<VectorSearchService.SearchResult> results) {
        if (results == null || results.isEmpty()) {
            return List.of();
        }
@@ -91,4 +201,11 @@ public class VectorKnowledgeSearchAdapter implements KnowledgeSearchPort {
            return Map.of();
        }
    }
+
+    private static String trimToNull(String value) {
+        if (value == null || value.isBlank()) {
+            return null;
+        }
+        return value.trim();
+    }
 }