Add boosting support

Author: carlosdelest

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/querydsl/query/KnnQuery.java

@@ -17,6 +17,7 @@
 import java.util.Map;
 import java.util.Objects;
 
+import static org.elasticsearch.index.query.AbstractQueryBuilder.BOOST_FIELD;
 import static org.elasticsearch.search.vectors.KnnVectorQueryBuilder.K_FIELD;
 import static org.elasticsearch.search.vectors.KnnVectorQueryBuilder.NUM_CANDS_FIELD;
 import static org.elasticsearch.search.vectors.KnnVectorQueryBuilder.VECTOR_SIMILARITY_FIELD;
@@ -48,7 +49,12 @@ protected QueryBuilder asBuilder() {
         }
         Float vectorSimilarity = (Float) options.get(VECTOR_SIMILARITY_FIELD.getPreferredName());
 
-        return new KnnVectorQueryBuilder(field, query, k, numCands, rescoreVectorBuilder, vectorSimilarity);
+        KnnVectorQueryBuilder queryBuilder = new KnnVectorQueryBuilder(field, query, k, numCands, rescoreVectorBuilder, vectorSimilarity);
+        Number boost = (Number) options.get(BOOST_FIELD.getPreferredName());
+        if (boost != null) {
+            queryBuilder.boost(boost.floatValue());
+        }
+        return queryBuilder;
     }
 
     @Override

x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/optimizer/LocalPhysicalPlanOptimizerTests.java

@@ -1909,7 +1909,7 @@ public void testMultiMatchOptionsPushDown() {
     public void testKnnOptionsPushDown() {
         String query = """
             from test
-            | where KNN(dense_vector, [0.1, 0.2, 0.3], { "k": 5, "similarity": 0.001, "num_candidates": 10, "rescore_oversample": 7 })
+            | where KNN(dense_vector, [0.1, 0.2, 0.3], { "k": 5, "similarity": 0.001, "num_candidates": 10, "rescore_oversample": 7, "boost": 3.5 })
             """;
         var analyzer = makeAnalyzer("mapping-all-types.json");
         var plan = plannerOptimizer.plan(query, IS_SV_STATS, analyzer);
@@ -1924,7 +1924,7 @@ public void testKnnOptionsPushDown() {
             10,
             new RescoreVectorBuilder(7),
             0.001f
-        );
+        ).boost(3.5f);
         assertThat(expectedQuery.toString(), is(planStr.get()));
     }