public static int get(final int[][] array, final long index) {
    return array[segment(index)][displacement(index)];
  }
Returns the element of the given big array of specified index.

@param array a big array.
@param index a position in the big array.
@return the element of the big array at the specified position.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/operator/source/relational/aggregation/grouped/array/IntBigArrays.java