Fix bug, support multiple aggregation (#771)

elasticsearch/src/main/java/com/amazon/opendistroforelasticsearch/sql/elasticsearch/response/ElasticsearchAggregationResponseParser.java

@@ -19,6 +19,7 @@
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.collect.ImmutableList;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -43,6 +44,7 @@ public class ElasticsearchAggregationResponseParser {
   public static List<Map<String, Object>> parse(Aggregations aggregations) {
     List<Aggregation> aggregationList = aggregations.asList();
     ImmutableList.Builder<Map<String, Object>> builder = new ImmutableList.Builder<>();
+    Map<String, Object> noBucketMap = new HashMap<>();
 
     for (Aggregation aggregation : aggregationList) {
       if (aggregation instanceof CompositeAggregation) {
@@ -51,11 +53,12 @@ public static List<Map<String, Object>> parse(Aggregations aggregations) {
           builder.add(parse(bucket));
         }
       } else {
-        builder.add(parseInternal(aggregation));
+        noBucketMap.putAll(parseInternal(aggregation));
       }
 
     }
-    return builder.build();
+    // Todo, there is no better way to difference the with/without bucket from aggregations result.
+    return noBucketMap.isEmpty() ? builder.build() : Collections.singletonList(noBucketMap);
   }
 
   private static Map<String, Object> parse(CompositeAggregation.Bucket bucket) {

elasticsearch/src/test/java/com/amazon/opendistroforelasticsearch/sql/elasticsearch/response/ElasticsearchAggregationResponseParserTest.java

@@ -61,7 +61,7 @@ void no_bucket_two_metric_should_pass() {
         + "  }\n"
         + "}";
     assertThat(parse(response),
-        containsInAnyOrder(entry("max", 40d), entry("min", 20d)));
+        contains(entry("max", 40d,"min", 20d)));
   }
 
   @Test
@@ -157,4 +157,8 @@ public List<Map<String, Object>> parse(String json) {
   public Map<String, Object> entry(String name, Object value) {
     return ImmutableMap.of(name, value);
   }
+
+  public Map<String, Object> entry(String name, Object value, String name2, Object value2) {
+    return ImmutableMap.of(name, value, name2, value2);
+  }
 }

integ-test/src/test/java/com/amazon/opendistroforelasticsearch/sql/ppl/StatsCommandIT.java

@@ -113,6 +113,17 @@ public void testGroupByNullValue() throws IOException {
     );
   }
 
+  //Todo. The column of agg function is in random order. This is because we create the project
+  // all operator from the symbol table which can't maintain the original column order.
+  @Test
+  public void testMultipleAggregationFunction() throws IOException {
+    JSONObject response = executeQuery(String.format(
+        "source=%s | stats min(age), max(age)",
+        TEST_INDEX_ACCOUNT));
+    verifySchema(response, schema("min(age)", null, "long"),
+        schema("max(age)", null, "long"));
+    verifyDataRows(response, rows(20, 40));
+  }
 
   @Test
   public void testStatsWithNull() throws IOException {