Say I have a feature called "size" and its text imput field. I have typed something in product details page say "small" or some number and I want to find this product among thousands of others that have nothing entered for this field. When it is a select box then sure you select and you find it but when its a text and you do not know what text how do you seach for this ? space * does not work.
I am trying to minimize list of features, some of them are not used but how can I know if some product is not assigned to this feature..