> For the complete documentation index, see [llms.txt](https://gunkim.gitbook.io/undefined/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://gunkim.gitbook.io/undefined/bloom-filter.md).

# bloom-filter

### 배운 개념

* 오탐(False Positive)은 해시 충돌 때문이며, 서로 다른 시드(Seed)를 통해 동일 데이터로 다중 해시값을 얻음.
* 오탐률을 낮추기 위해 해시 개수만 늘려선 안 되고 본질적으로 **'비트 배열 크기(도화지)'를 키워야 함**.
* 지정된 비트를 1로 마스킹하므로, 나중에 검사할 때 하나라도 0이라면 100% 없음을 보장함.

### 오답 및 정정

> \[!WARNING] **오개념**: 블룸 필터 오탐률을 줄이려면 해시 함수 개수만 무작정 늘리면 된다. **정정**: 본질적으로 전체 비트 배열의 크기(메모리)를 늘려야 해시 충돌이 줄어듦.

### 복습 체크

* [ ] 블룸 필터가 '확실히 없음'은 보장하지만 '확실히 있음'은 보장하지 못하는 이유는 무엇인가?
* [ ] 오탐률을 획기적으로 낮추려면 어떤 조치를 취해야 하는가?

\[\[lsm-tree]]


---

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