public void reset() {
    array.forEach(
        v -> {
          if (v != null) {
            v.clear();
          }
        });
  }
Ensures this big array is at least the specified length. If the array is smaller, segments are
added until the array is larger then the specified length.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/operator/source/relational/aggregation/grouped/array/MapBigArray.java