IDBObjectStore/IDBIndex.exists(key)

Hi all,

I found an old email with notes about features that we might want to put in
v2.

Almost all of them was recently brought up in the recent threads about
IDBv2. However there was one thing on the list that I haven't seen brought
up.

It might be a nice perf improvement to add support for a
IDBObjectStore/IDBIndex.exists(key) function.

This would require less IO and less object creation than simply using
.get(). It is probably particularly useful when doing a filtering join
operation between two indexes/object stores. But it is probably useful
other times too.

Is this something that others think would be useful?

/ Jonas