posts: bloom-filter: add lookup

This commit is contained in:
Bruno BELANYI 2024-07-14 17:56:33 +01:00
parent 2c31c1aff2
commit 27152689ea

View file

@ -77,3 +77,21 @@ def insert(self, val: T) -> None:
# Set the corresponding bit
self._bit |= 1 << n
```
### Querying a key
Because the _Bloom Filter_ does not actually store its elements, but some
derived data from hashing them, it can only definitely say if an element _does
not_ belong to it. Otherwise, it _may_ be part of the set, and should be checked
against the actual underlying store.
```python
def may_contain(self, val: T) -> bool:
for f in self._hash_functions:
n = f(val) % BIT_COUNT
# If one of the bits is unset, the value is definitely not present
if not (self._bit & (1 << n)):
return False
# All bits were matched, `val` is likely to be part of the set
return True
```