Mutate function not working (Logstash 6.2.4)

file {
path => "C:/Users/Desktop/test1///Erreurs/*.csv"
start_position => "beginning"
}

You know that this configuration won't cause the file to be read every time you run Logstash, right? The start_position option only matters the first time an input file is seen. Read what's said about sincedb in the file input documentation.