How to delete only descendant members of a parent in EPBCS using groovy script

We have a requirement to delete Purchase requisitions every time we load the transactional data. To achieve this we want to use a groovy Business rule to delete the descendants of a parent member and rebuild them every time to handle performance issues. But the challenge is that every time it deletes the parent as well. Is there a way we can only delete the descendants of a Parent using Groovy so that we can call this rule in Data Management.