Reducing a field's size

I have a standard LAMP stack website with a log table which stores some basic information, there is an additional field in there which serializes an array and stores (such as the POST data) if it’s relevant to the entry.

My question is, what are some ways I could reduce the space that this field (currently a LONGTEXT) takes us as it’s rarely ever read, so output speed/efficiency is of no matter, it’s just currently very large as there’s no compression of any sort.

try to changed your datatype into a text type only and don’t put a numbers of characters in short it infinite characters will be inputed to this field.