This is kind of a fundamental part of bloom filters. They're probabilistic data structures, which is the trade you make for space efficiency.
If you get a false back, you can guarantee that some item is not in the filter. If you get a true back, you can be fairly certain it is. Once you have a degree of certainty, you can do a more thorough check for membership while cutting out large numbers of negatives.
If you get a false back, you can guarantee that some item is not in the filter. If you get a true back, you can be fairly certain it is. Once you have a degree of certainty, you can do a more thorough check for membership while cutting out large numbers of negatives.