Remove an unnecessary bucket agg in AggregationQueryBuilder

Signed-off-by: Yuanchun Shen <yuanchu@amazon.com>

Author: yuancu

opensearch/src/main/java/org/opensearch/sql/opensearch/storage/script/aggregation/AggregationQueryBuilder.java

@@ -29,7 +29,6 @@
 import org.opensearch.sql.expression.ReferenceExpression;
 import org.opensearch.sql.expression.aggregation.NamedAggregator;
 import org.opensearch.sql.opensearch.data.type.OpenSearchDataType;
-import org.opensearch.sql.opensearch.response.agg.BucketAggregationParser;
 import org.opensearch.sql.opensearch.response.agg.LeafBucketAggregationParser;
 import org.opensearch.sql.opensearch.response.agg.MetricParser;
 import org.opensearch.sql.opensearch.response.agg.NoBucketAggregationParser;
@@ -96,7 +95,7 @@ public AggregationQueryBuilder(ExpressionSerializer serializer) {
                           bucketNullable))
                   .subAggregations(metrics.getLeft())
                   .size(AGGREGATION_BUCKET_SIZE)),
-          new BucketAggregationParser(new LeafBucketAggregationParser(metrics.getRight())));
+          new LeafBucketAggregationParser(metrics.getRight()));
     }
   }
 

opensearch/src/test/java/org/opensearch/sql/opensearch/storage/scan/OpenSearchIndexScanOptimizationTest.java

@@ -74,7 +74,6 @@
 import org.opensearch.sql.expression.function.OpenSearchFunctions;
 import org.opensearch.sql.opensearch.data.type.OpenSearchDataType;
 import org.opensearch.sql.opensearch.request.OpenSearchRequestBuilder;
-import org.opensearch.sql.opensearch.response.agg.BucketAggregationParser;
 import org.opensearch.sql.opensearch.response.agg.LeafBucketAggregationParser;
 import org.opensearch.sql.opensearch.response.agg.OpenSearchAggregationResponseParser;
 import org.opensearch.sql.opensearch.response.agg.SingleValueParser;
@@ -804,8 +803,7 @@ private Runnable withAggregationPushedDown(
             .size(AggregationQueryBuilder.AGGREGATION_BUCKET_SIZE);
     List<AggregationBuilder> aggBuilders = Collections.singletonList(aggBuilder);
     responseParser =
-        new BucketAggregationParser(
-            new LeafBucketAggregationParser(new SingleValueParser(aggregation.aggregateName)));
+        new LeafBucketAggregationParser(new SingleValueParser(aggregation.aggregateName));
 
     return () -> {
       verify(requestBuilder, times(1)).pushDownAggregation(Pair.of(aggBuilders, responseParser));