I have a table with a lot of place names. There are much too many names for all of them to be shown on the print composer map. Some names are important, and in the column fontsize these have a bigger font size number (for instance 270). I want to prioritize bigger font size names over smaller font size names. So I go to Layer Properties -> Labels -> Placement -> and in Priority chose a data defined override by selecting the field fontsize .
Should this work? It does not give rational results, as some smaller labels are still shown instead of bigger ones.
Qgis version 2.18.7