Check existence of a field and checking null value in field

I have different types of logs generated by the software we user in one big file. I am trying to assign "log_type" to different types of logs in my file. Since they have different number of columns(I used csv plugin to parse them), I tried to differentiate them by checking the existence of unique field. In the below example, the top event doesn't have column 16, but the bottom one does.

So my config looked like this:

if [column16] {
... "type1"
}else {
... "type2"

but as it shows in the picture, they got assigned the same type number, I think the above if statement doesn't work, it can't tell the difference between a null value in the field and the field doesn't exist.

any suggestions?

There does not seem to be a straightforward way to accomplish this.

I suggest using the ruby filter for now to call event.include?("[column16]") and add a tag based on that or something so that you can continue with your normal branch conditionals.

filed an issue for this here:

Developing further the idea of using the ruby filter, can you try something like this?

                    code => "
					if event['column16'] == nil
						event['log_type'] = 'type2'
						event['log_type'] = 'type1'