Yes, this is the idea. I set the threshold for approximate search with a margin so that on a few test queries, I get 100% recall, and then it is filtered by pre

Yes, this is the idea. I set the threshold for approximate search with a margin so that on a few test queries, I get 100% recall, and then it is filtered by precise search. But I didn't evaluate it thoroughly. The threshold for Hamming distance over bit masks was set almost arbitrarily, and it will be interesting to test further.