Plan correct encoder for exponential histograms

Author: JonasKunz

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/planner/LocalExecutionPlanner.java

@@ -487,10 +487,9 @@ private PhysicalOperation planTopN(TopNExec topNExec, LocalExecutionPlannerConte
                 case BOOLEAN, NULL, BYTE, SHORT, INTEGER, LONG, DOUBLE, FLOAT, HALF_FLOAT, DATETIME, DATE_NANOS, DATE_PERIOD, TIME_DURATION,
                     OBJECT, SCALED_FLOAT, UNSIGNED_LONG, TSID_DATA_TYPE -> TopNEncoder.DEFAULT_SORTABLE;
                 case GEO_POINT, CARTESIAN_POINT, GEO_SHAPE, CARTESIAN_SHAPE, COUNTER_LONG, COUNTER_INTEGER, COUNTER_DOUBLE, SOURCE,
-                    AGGREGATE_METRIC_DOUBLE, DENSE_VECTOR, GEOHASH, GEOTILE, GEOHEX -> TopNEncoder.DEFAULT_UNSORTABLE;
+                    AGGREGATE_METRIC_DOUBLE, DENSE_VECTOR, GEOHASH, GEOTILE, GEOHEX, EXPONENTIAL_HISTOGRAM -> TopNEncoder.DEFAULT_UNSORTABLE;
                 // unsupported fields are encoded as BytesRef, we'll use the same encoder; all values should be null at this point
-                // TODO(b/133393) add exponential histogram support
-                case PARTIAL_AGG, EXPONENTIAL_HISTOGRAM, UNSUPPORTED -> TopNEncoder.UNSUPPORTED;
+                case PARTIAL_AGG, UNSUPPORTED -> TopNEncoder.UNSUPPORTED;
             };
         }
         List<TopNOperator.SortOrder> orders = topNExec.order().stream().map(order -> {