Hybrid Retriever POC - DO NOT MERGE

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

@@ -279,16 +279,16 @@ public final boolean equals(Object o) {
         if (this == o) return true;
         if (o == null || getClass() != o.getClass()) return false;
         RetrieverBuilder that = (RetrieverBuilder) o;
-        return Objects.equals(preFilterQueryBuilders, that.preFilterQueryBuilders)
-            && Objects.equals(minScore, that.minScore)
+        return Objects.equals(getPreFilterQueryBuilders(), that.getPreFilterQueryBuilders())
+            && Objects.equals(minScore(), that.minScore())
             && doEquals(o);
     }
 
     protected abstract boolean doEquals(Object o);
 
     @Override
     public final int hashCode() {
-        return Objects.hash(getClass(), preFilterQueryBuilders, minScore, doHashCode());
+        return Objects.hash(getClass(), getPreFilterQueryBuilders(), minScore(), doHashCode());
     }
 
     protected abstract int doHashCode();

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

@@ -104,6 +104,10 @@ private StandardRetrieverBuilder(StandardRetrieverBuilder clone) {
         this.terminateAfter = clone.terminateAfter;
     }
 
+    public QueryBuilder getQueryBuilder() {
+        return queryBuilder;
+    }
+
     @Override
     public RetrieverBuilder rewrite(QueryRewriteContext ctx) throws IOException {
         boolean changed = false;

x-pack/plugin/inference/src/main/java/module-info.java

@@ -43,6 +43,7 @@
     exports org.elasticsearch.xpack.inference;
     exports org.elasticsearch.xpack.inference.action.task;
     exports org.elasticsearch.xpack.inference.telemetry;
+    exports org.elasticsearch.xpack.inference.rank.textsimilarity;
 
     provides org.elasticsearch.features.FeatureSpecification with org.elasticsearch.xpack.inference.InferenceFeatures;
 }

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

@@ -23,6 +23,7 @@
 import org.elasticsearch.xcontent.XContentParser;
 
 import java.io.IOException;
+import java.util.ArrayList;
 import java.util.List;
 import java.util.Objects;
 
@@ -49,7 +50,7 @@ public class TextSimilarityRankRetrieverBuilder extends CompoundRetrieverBuilder
     public static final ConstructingObjectParser<TextSimilarityRankRetrieverBuilder, RetrieverParserContext> PARSER =
         new ConstructingObjectParser<>(TextSimilarityRankBuilder.NAME, args -> {
             RetrieverBuilder retrieverBuilder = (RetrieverBuilder) args[0];
-            String inferenceId = args[1] == null ? DEFAULT_RERANK_ID : (String) args[1];
+            String inferenceId = (String) args[1];
             String inferenceText = (String) args[2];
             String field = (String) args[3];
             int rankWindowSize = args[4] == null ? DEFAULT_RANK_WINDOW_SIZE : (int) args[4];
@@ -104,11 +105,17 @@ public TextSimilarityRankRetrieverBuilder(
         int rankWindowSize,
         boolean failuresAllowed
     ) {
-        super(List.of(new RetrieverSource(retrieverBuilder, null)), rankWindowSize);
-        this.inferenceId = inferenceId;
-        this.inferenceText = inferenceText;
-        this.field = field;
-        this.failuresAllowed = failuresAllowed;
+        this(
+            List.of(new RetrieverSource(retrieverBuilder, null)),
+            inferenceId,
+            inferenceText,
+            field,
+            rankWindowSize,
+            null,
+            failuresAllowed,
+            null,
+            new ArrayList<>()
+        );
     }
 
     public TextSimilarityRankRetrieverBuilder(
@@ -124,9 +131,11 @@ public TextSimilarityRankRetrieverBuilder(
     ) {
         super(retrieverSource, rankWindowSize);
         if (retrieverSource.size() != 1) {
-            throw new IllegalArgumentException("[" + getName() + "] retriever should have exactly one inner retriever");
+            throw new IllegalArgumentException(
+                "[" + TextSimilarityRankBuilder.NAME + "] retriever should have exactly one inner retriever"
+            );
         }
-        this.inferenceId = inferenceId;
+        this.inferenceId = inferenceId == null ? DEFAULT_RERANK_ID : inferenceId;
         this.inferenceText = inferenceText;
         this.field = field;
         this.minScore = minScore;

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

@@ -13,11 +13,12 @@ esplugin {
   name = 'rank-rrf'
   description = 'Reciprocal rank fusion in search.'
   classname ='org.elasticsearch.xpack.rank.rrf.RRFRankPlugin'
-  extendedPlugins = ['x-pack-core']
+  extendedPlugins = ['x-pack-core', 'x-pack-inference']
 }
 
 dependencies {
   compileOnly project(path: xpackModule('core'))
+  compileOnly project(path: xpackModule('inference'))
 
   testImplementation(testArtifact(project(xpackModule('core'))))
   testImplementation(testArtifact(project(':server')))

x-pack/plugin/rank-rrf/src/main/java/module-info.java

@@ -13,6 +13,7 @@
     requires org.elasticsearch.xcontent;
     requires org.elasticsearch.server;
     requires org.elasticsearch.xcore;
+    requires org.elasticsearch.inference;
 
     exports org.elasticsearch.xpack.rank;
     exports org.elasticsearch.xpack.rank.rrf;