Using the BULK api and the index action on each entry.
Suppose I have an index pattern "myindex-*".
ILM is in play creating "myindex-00001", "myindex-00002", etc....
Day one a document is POSTed to the rollover alias "myindex_insert" using a user supplied Document ID of "0000000000001".
Since this is the first POST "0000000000001" will obviously be stored in "myindex-00001" as I understand it.
Day two ILM "fires" and now "myindex_insert" is pointing to "myindex-00002".
What will happen when Document ID "0000000000001" is used again against "myindex_insert"?
I believe I'll get 2 entries with Document ID "0000000000001" in 2 indexes since an index pattern is not an index but a way to search a list of indexes and the scope of uniqueness for a Document ID is the index itself not the index pattern covering a list of indexes.