Loading collection data...
Collections are a way for you to organize kata so that you can create your own training routines. Every collection you create is public and automatically sharable with other warriors. After you have added a few kata to a collection you and others can train on the kata contained within the collection.
Get started now by creating a new collection.
Did you check the explain plan? Not exists supposed to stop processing it after finding the first record. It does not check every matching row. So adding lmit 1 shouldn't change anything.
in my opinion it can be boosted by adding limit 1 before where-statement to stop as minimum 80% of calculations