SQL: Fix result values for COUNT(DISTINCT ...) (#68666)

Previously, we extracted the result of the `CardinalityAgg` as `double`
which resulted in values shown in the REST response with `.0`, even though
the type of the corresponding column for `COUNT(DISTINCT <field_name>)`
was showing `long`, e.g.: `152.0` instead of `152`.
This affected only the REST interface of SQL and not the JDBC/ODBC drivers.

Extract a long value instead of a double.

Fixes: #58097

x-pack/plugin/sql/qa/server/src/main/java/org/elasticsearch/xpack/sql/qa/rest/RestSqlTestCase.java

@@ -418,6 +418,50 @@ public abstract class RestSqlTestCase extends BaseRestSqlTestCase implements Err
         );
     }
 
+    public void testCountAndCountDistinct() throws IOException {
+        String mode = randomMode();
+        index(
+            "test",
+            "{\"gender\":\"m\", \"langs\": 1}",
+            "{\"gender\":\"m\", \"langs\": 1}",
+            "{\"gender\":\"m\", \"langs\": 2}",
+            "{\"gender\":\"m\", \"langs\": 3}",
+            "{\"gender\":\"m\", \"langs\": 3}",
+            "{\"gender\":\"f\", \"langs\": 1}",
+            "{\"gender\":\"f\", \"langs\": 2}",
+            "{\"gender\":\"f\", \"langs\": 2}",
+            "{\"gender\":\"f\", \"langs\": 2}",
+            "{\"gender\":\"f\", \"langs\": 3}",
+            "{\"gender\":\"f\", \"langs\": 3}"
+        );
+
+        Map<String, Object> expected = new HashMap<>();
+        boolean columnar = randomBoolean();
+        expected.put(
+            "columns",
+            Arrays.asList(
+                columnInfo(mode, "gender", "text", JDBCType.VARCHAR, Integer.MAX_VALUE),
+                columnInfo(mode, "cnt", "long", JDBCType.BIGINT, 20),
+                columnInfo(mode, "cnt_dist", "long", JDBCType.BIGINT, 20)
+            )
+        );
+        if (columnar) {
+            expected.put("values", Arrays.asList(Arrays.asList("f", "m"), Arrays.asList(6, 5), Arrays.asList(3, 3)));
+        } else {
+            expected.put("rows", Arrays.asList(Arrays.asList("f", 6, 3), Arrays.asList("m", 5, 3)));
+        }
+
+        Map<String, Object> response = runSql(
+            mode,
+            "SELECT gender, COUNT(langs) AS cnt, COUNT(DISTINCT langs) AS cnt_dist " + "FROM test GROUP BY gender ORDER BY gender",
+            columnar
+        );
+
+        String cursor = (String) response.remove("cursor");
+        assertNotNull(cursor);
+        assertResponse(expected, response);
+    }
+
     @Override
     public void testSelectScoreSubField() throws Exception {
         index("{\"foo\":1}");

x-pack/plugin/sql/src/main/java/org/elasticsearch/xpack/sql/execution/search/extractor/MetricAggExtractor.java

@@ -13,6 +13,7 @@ import org.elasticsearch.search.aggregations.bucket.MultiBucketsAggregation.Buck
 import org.elasticsearch.search.aggregations.bucket.filter.InternalFilter;
 import org.elasticsearch.search.aggregations.matrix.stats.InternalMatrixStats;
 import org.elasticsearch.search.aggregations.metrics.InternalAvg;
+import org.elasticsearch.search.aggregations.metrics.InternalCardinality;
 import org.elasticsearch.search.aggregations.metrics.InternalMax;
 import org.elasticsearch.search.aggregations.metrics.InternalMin;
 import org.elasticsearch.search.aggregations.metrics.InternalNumericMetricsAggregation;
@@ -25,7 +26,6 @@ import org.elasticsearch.xpack.sql.SqlIllegalArgumentException;
 import org.elasticsearch.xpack.sql.common.io.SqlStreamInput;
 import org.elasticsearch.xpack.sql.querydsl.agg.Aggs;
 import org.elasticsearch.xpack.sql.util.DateUtils;
-
 import java.io.IOException;
 import java.time.ZoneId;
 import java.util.Map;
@@ -110,6 +110,8 @@ public class MetricAggExtractor implements BucketExtractor {
         } else if (agg instanceof InternalFilter) {
             // COUNT(expr) and COUNT(ALL expr) uses this type of aggregation to account for non-null values only
             return ((InternalFilter) agg).getDocCount();
+        } else if (agg instanceof InternalCardinality) {
+            return ((InternalCardinality) agg).getValue();
         }
 
         Object v = agg.getProperty(property);