Hongzheng Li

When calling `get_string` or `get_html_string` or `get_latex_string` and passing `fields = ["field1", "field2"]` as the parameter, the output strings in either format contain the given fields in `fields` only. However,...

Fix the bug which leads to duplicate the output of the last sorted chunk file.

Fix bug in merging when comparing function is NULL, use operator reloading instead.