[8.19] Simplified Linear Retriever (#129200)

docs/changelog/129200.yaml

@@ -0,0 +1,5 @@
+pr: 129200
+summary: Simplified Linear Retriever
+area: Search
+type: enhancement
+issues: []

server/src/main/java/org/elasticsearch/search/retriever/CompoundRetrieverBuilder.java

@@ -36,6 +36,7 @@
 
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.Locale;
 import java.util.Objects;
@@ -53,7 +54,11 @@ public abstract class CompoundRetrieverBuilder<T extends CompoundRetrieverBuilde
 
     public static final ParseField RANK_WINDOW_SIZE_FIELD = new ParseField("rank_window_size");
 
-    public record RetrieverSource(RetrieverBuilder retriever, SearchSourceBuilder source) {}
+    public record RetrieverSource(RetrieverBuilder retriever, SearchSourceBuilder source) {
+        public static RetrieverSource from(RetrieverBuilder retriever) {
+            return new RetrieverSource(retriever, null);
+        }
+    }
 
     protected final int rankWindowSize;
     protected final List<RetrieverSource> innerRetrievers;
@@ -65,7 +70,7 @@ protected CompoundRetrieverBuilder(List<RetrieverSource> innerRetrievers, int ra
 
     @SuppressWarnings("unchecked")
     public T addChild(RetrieverBuilder retrieverBuilder) {
-        innerRetrievers.add(new RetrieverSource(retrieverBuilder, null));
+        innerRetrievers.add(RetrieverSource.from(retrieverBuilder));
         return (T) this;
     }
 
@@ -99,6 +104,11 @@ public final RetrieverBuilder rewrite(QueryRewriteContext ctx) throws IOExceptio
             throw new IllegalStateException("PIT is required");
         }
 
+        RetrieverBuilder rewritten = doRewrite(ctx);
+        if (rewritten != this) {
+            return rewritten;
+        }
+
         // Rewrite prefilters
         // We eagerly rewrite prefilters, because some of the innerRetrievers
         // could be compound too, so we want to propagate all the necessary filter information to them
@@ -121,7 +131,7 @@ public final RetrieverBuilder rewrite(QueryRewriteContext ctx) throws IOExceptio
             }
             RetrieverBuilder newRetriever = entry.retriever.rewrite(ctx);
             if (newRetriever != entry.retriever) {
-                newRetrievers.add(new RetrieverSource(newRetriever, null));
+                newRetrievers.add(RetrieverSource.from(newRetriever));
                 hasChanged |= true;
             } else {
                 var sourceBuilder = entry.source != null
@@ -291,6 +301,10 @@ public int rankWindowSize() {
         return rankWindowSize;
     }
 
+    public List<RetrieverSource> innerRetrievers() {
+        return Collections.unmodifiableList(innerRetrievers);
+    }
+
     protected final SearchSourceBuilder createSearchSourceBuilder(PointInTimeBuilder pit, RetrieverBuilder retrieverBuilder) {
         var sourceBuilder = new SearchSourceBuilder().pointInTimeBuilder(pit)
             .trackTotalHits(false)
@@ -317,6 +331,16 @@ protected SearchSourceBuilder finalizeSourceBuilder(SearchSourceBuilder sourceBu
         return sourceBuilder;
     }
 
+    /**
+     * Perform any custom rewrite logic necessary
+     *
+     * @param ctx The query rewrite context
+     * @return RetrieverBuilder the rewritten retriever
+     */
+    protected RetrieverBuilder doRewrite(QueryRewriteContext ctx) {
+        return this;
+    }
+
     private RankDoc[] getRankDocs(SearchResponse searchResponse) {
         int size = searchResponse.getHits().getHits().length;
         RankDoc[] docs = new RankDoc[size];

server/src/main/java/org/elasticsearch/search/retriever/RescorerRetrieverBuilder.java

@@ -78,7 +78,7 @@ public static RescorerRetrieverBuilder fromXContent(XContentParser parser, Retri
     private final List<RescorerBuilder<?>> rescorers;
 
     public RescorerRetrieverBuilder(RetrieverBuilder retriever, List<RescorerBuilder<?>> rescorers) {
-        super(List.of(new RetrieverSource(retriever, null)), extractMinWindowSize(rescorers));
+        super(List.of(RetrieverSource.from(retriever)), extractMinWindowSize(rescorers));
         if (rescorers.isEmpty()) {
             throw new IllegalArgumentException("Missing rescore definition");
         }

x-pack/plugin/inference/build.gradle

@@ -404,5 +404,5 @@ tasks.named("thirdPartyAudit").configure {
 }
 
 tasks.named('yamlRestTest') {
-  usesDefaultDistribution()
+  usesDefaultDistribution("Uses the inference API")
 }

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/rank/textsimilarity/TextSimilarityRankRetrieverBuilder.java

@@ -124,7 +124,7 @@ public TextSimilarityRankRetrieverBuilder(
         int rankWindowSize,
         boolean failuresAllowed
     ) {
-        super(List.of(new RetrieverSource(retrieverBuilder, null)), rankWindowSize);
+        super(List.of(RetrieverSource.from(retrieverBuilder)), rankWindowSize);
         this.inferenceId = inferenceId;
         this.inferenceText = inferenceText;
         this.field = field;

x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/queries/SemanticMultiMatchQueryBuilderTests.java

@@ -0,0 +1,125 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+package org.elasticsearch.xpack.inference.queries;
+
+import org.apache.lucene.index.Term;
+import org.apache.lucene.search.DisjunctionMaxQuery;
+import org.apache.lucene.search.Query;
+import org.apache.lucene.search.TermQuery;
+import org.elasticsearch.cluster.ClusterChangedEvent;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.core.IOUtils;
+import org.elasticsearch.index.mapper.MapperService;
+import org.elasticsearch.index.mapper.MapperServiceTestCase;
+import org.elasticsearch.index.mapper.ParsedDocument;
+import org.elasticsearch.index.query.MultiMatchQueryBuilder;
+import org.elasticsearch.index.query.SearchExecutionContext;
+import org.elasticsearch.plugins.Plugin;
+import org.elasticsearch.test.ClusterServiceUtils;
+import org.elasticsearch.test.client.NoOpClient;
+import org.elasticsearch.threadpool.TestThreadPool;
+import org.elasticsearch.xpack.inference.InferencePlugin;
+import org.elasticsearch.xpack.inference.registry.ModelRegistry;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+
+import java.util.Collection;
+import java.util.List;
+import java.util.function.Supplier;
+
+public class SemanticMultiMatchQueryBuilderTests extends MapperServiceTestCase {
+    private static TestThreadPool threadPool;
+    private static ModelRegistry modelRegistry;
+
+    private static class InferencePluginWithModelRegistry extends InferencePlugin {
+        InferencePluginWithModelRegistry(Settings settings) {
+            super(settings);
+        }
+
+        @Override
+        protected Supplier<ModelRegistry> getModelRegistry() {
+            return () -> modelRegistry;
+        }
+    }
+
+    @BeforeClass
+    public static void startModelRegistry() {
+        threadPool = new TestThreadPool(SemanticMultiMatchQueryBuilderTests.class.getName());
+        var clusterService = ClusterServiceUtils.createClusterService(threadPool);
+        modelRegistry = new ModelRegistry(clusterService, new NoOpClient(threadPool));
+        modelRegistry.clusterChanged(new ClusterChangedEvent("init", clusterService.state(), clusterService.state()) {
+            @Override
+            public boolean localNodeMaster() {
+                return false;
+            }
+        });
+    }
+
+    @AfterClass
+    public static void stopModelRegistry() {
+        IOUtils.closeWhileHandlingException(threadPool);
+    }
+
+    @Override
+    protected Collection<? extends Plugin> getPlugins() {
+        return List.of(new InferencePluginWithModelRegistry(Settings.EMPTY));
+    }
+
+    public void testResolveSemanticTextFieldFromWildcard() throws Exception {
+        MapperService mapperService = createMapperService("""
+            {
+              "_doc" : {
+                "properties": {
+                  "text_field": { "type": "text" },
+                  "keyword_field": { "type": "keyword" },
+                  "inference_field": { "type": "semantic_text", "inference_id": "test_service" }
+                }
+              }
+            }
+            """);
+
+        ParsedDocument doc = mapperService.documentMapper().parse(source("""
+            {
+              "text_field" : "foo",
+              "keyword_field" : "foo",
+              "inference_field" : "foo",
+              "_inference_fields": {
+                "inference_field": {
+                  "inference": {
+                    "inference_id": "test_service",
+                    "model_settings": {
+                      "task_type": "sparse_embedding"
+                    },
+                    "chunks": {
+                      "inference_field": [
+                        {
+                          "start_offset": 0,
+                          "end_offset": 3,
+                          "embeddings": {
+                            "foo": 1.0
+                          }
+                        }
+                      ]
+                    }
+                  }
+                }
+              }
+            }
+            """));
+
+        withLuceneIndex(mapperService, iw -> iw.addDocument(doc.rootDoc()), ir -> {
+            SearchExecutionContext context = createSearchExecutionContext(mapperService, newSearcher(ir));
+            Query query = new MultiMatchQueryBuilder("foo", "*_field").toQuery(context);
+            Query expected = new DisjunctionMaxQuery(
+                List.of(new TermQuery(new Term("text_field", "foo")), new TermQuery(new Term("keyword_field", "foo"))),
+                0f
+            );
+            assertEquals(expected, query);
+        });
+    }
+}

x-pack/plugin/rank-rrf/build.gradle

@@ -30,3 +30,7 @@ dependencies {
 
   clusterPlugins project(':x-pack:plugin:inference:qa:test-service-plugin')
 }
+
+tasks.named('yamlRestTest') {
+  usesDefaultDistribution("Uses the inference API")
+}