parquet-column/src/main/java/org/apache/parquet/internal/column/columnindex/ColumnIndexBuilder.java
private boolean isDescending(PrimitiveComparator<Binary> comparator) {
    for (int i = 1, n = pageIndexes.size(); i < n; ++i) {
      if (compareMinValues(comparator, i - 1, i) < 0 || compareMaxValues(comparator, i - 1, i) < 0) {
        return false;
      }
    }
    return true;
  }
private boolean isDescending(PrimitiveComparator<Binary> comparator) {
    for (int i = 1, n = pageIndexes.size(); i < n; ++i) {
      if (compareMinValues(comparator, i - 1, i) < 0 || compareMaxValues(comparator, i - 1, i) < 0) {
        return false;
      }
    }
    return true;
  }
min[i] >= min[i+1] && max[i] >= max[i+1]