how we can assign a default value for empty tag with KV_MODE=xml?

[imgarytan]

Hi folks,

Any idea how we can assign a default value for empty tag with KV_MODE=xml?

The reason is, we have a xml segment repeated multiple times under same parent/grandparent, as such same tag names (xpath) repeated multiple times. So one field for each tag name is extracted with a mv value.
Now the issue is if some of the tag in the middle is empty, it will mess up the mv index in these fields.
And we need the full xpath as the field name, so it is hard to do a manual generic field extraction ($1::$2) either. 

A quick thought is if we can fill up a special value in the raw, then all mv fields will stay well aligned. But is this the only option?

Any suggestion or better solution?
Or can we do it at search time with sonething like " | rex field=ccnumber mode=sed ..."

Thanks a lot

[imgarytan]

Or can we maintain the MV index, to have a mv value like below? so if the third tag is empty, then keep the empty value stay in the right index?
A
B

D