I am looking for a simple and efficient way to delete all data from an index without deleting the index. This is known as a truncate in SQL parlance.
The rationale is that I want to clear the data while leaving typing and permissions intact. Both typing and permissions are complicated and it's not something I want to do repeatedly anyway.
This posting asks the same question and goes like this: "You can use delete by query, but it's seriously inefficient." "What if I don't care that it's inefficient?" "Why not just delete it and repopulate?"
So I open a feature request which gets summarily closed with "use delete by query". This is a fundamental feature which deserves a good answer.