LONG_STRING_COLUMNS dont't have effect

[Jocean shi]

The paramter  LONG_STRING_COLUMNS dont't have effect.
I try the two way:
first: TBLPROPERTIES ('LONG_STRING_COLUMNS'='col1,col2')
second: df.format("carbondata")
.option("tableName", "carbonTable")
  .option("long_string_columns", "col1, col2")
  .save()