optimization MetricsEsDAO multiGet (#5096)

oap-server/server-storage-plugin/storage-elasticsearch-plugin/src/main/java/org/apache/skywalking/oap/server/storage/plugin/elasticsearch/base/MetricsEsDAO.java

@@ -44,8 +44,8 @@ public class MetricsEsDAO extends EsDAO implements IMetricsDAO {
     public List<Metrics> multiGet(Model model, List<String> ids) throws IOException {
         SearchResponse response = getClient().ids(model.getName(), ids.toArray(new String[0]));
 
-        List<Metrics> result = new ArrayList<>((int) response.getHits().totalHits);
-        for (int i = 0; i < response.getHits().totalHits; i++) {
+        List<Metrics> result = new ArrayList<>(response.getHits().getHits().length);
+        for (int i = 0; i < response.getHits().getHits().length; i++) {
             Metrics source = storageBuilder.map2Data(response.getHits().getAt(i).getSourceAsMap());
             result.add(source);
         }

oap-server/server-storage-plugin/storage-elasticsearch7-plugin/src/main/java/org/apache/skywalking/oap/server/storage/plugin/elasticsearch7/dao/MetricsEs7DAO.java

@@ -39,8 +39,8 @@ public class MetricsEs7DAO extends MetricsEsDAO {
     public List<Metrics> multiGet(Model model, List<String> ids) throws IOException {
         SearchResponse response = getClient().ids(model.getName(), ids.toArray(new String[0]));
 
-        List<Metrics> result = new ArrayList<>((int) response.getHits().getTotalHits().value);
-        for (int i = 0; i < response.getHits().getTotalHits().value; i++) {
+        List<Metrics> result = new ArrayList<>(response.getHits().getHits().length);
+        for (int i = 0; i < response.getHits().getHits().length; i++) {
             Metrics source = storageBuilder.map2Data(response.getHits().getAt(i).getSourceAsMap());
             result.add(source);
         }