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uniface/docs/modules/stores.md
Yakhyokhuja Valikhujaev 426bd71505 release: Release UniFace v3.3.0 - Python 3.10 support, stores refactor, docs and examples refresh (#101)
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# Stores
FAISS-backed vector store for fast similarity search over embeddings.
!!! info "Optional dependency"
```bash
pip install faiss-cpu
```
---
## FAISS
```python
from uniface.stores import FAISS
```
A thin wrapper around a FAISS `IndexFlatIP` (inner-product) index. Vectors
**must** be L2-normalised before adding so that inner product equals cosine
similarity. The store does not normalise internally.
Each vector is paired with a metadata `dict` that can carry any
JSON-serialisable payload (person ID, name, source path, etc.).
### Constructor
```python
store = FAISS(embedding_size=512, db_path="./vector_index")
```
| Parameter | Type | Default | Description |
|-----------|------|---------|-------------|
| `embedding_size` | `int` | `512` | Dimension of embedding vectors |
| `db_path` | `str` | `"./vector_index"` | Directory for persisting index and metadata |
---
### Methods
#### `add(embedding, metadata)`
Add a single embedding with associated metadata.
```python
store.add(embedding, {"person_id": "alice", "source": "photo.jpg"})
```
| Parameter | Type | Description |
|-----------|------|-------------|
| `embedding` | `np.ndarray` | L2-normalised embedding vector |
| `metadata` | `dict[str, Any]` | Arbitrary JSON-serialisable key-value pairs |
---
#### `search(embedding, threshold=0.4)`
Find the closest match for a query embedding.
```python
result, similarity = store.search(query_embedding, threshold=0.4)
if result:
print(result["person_id"], similarity)
```
| Parameter | Type | Default | Description |
|-----------|------|---------|-------------|
| `embedding` | `np.ndarray` | — | L2-normalised query vector |
| `threshold` | `float` | `0.4` | Minimum cosine similarity to accept a match |
**Returns:** `(metadata, similarity)` if a match is found, or `(None, similarity)` when below threshold or the index is empty.
---
#### `remove(key, value)`
Remove all entries where `metadata[key] == value` and rebuild the index.
```python
removed = store.remove("person_id", "bob")
print(f"Removed {removed} entries")
```
| Parameter | Type | Description |
|-----------|------|-------------|
| `key` | `str` | Metadata key to match |
| `value` | `Any` | Value to match |
**Returns:** Number of entries removed.
---
#### `save()`
Persist the FAISS index and metadata to disk.
```python
store.save()
```
Writes two files to `db_path`:
- `faiss_index.bin` — binary FAISS index
- `metadata.json` — JSON array of metadata dicts
---
#### `load()`
Load a previously saved index and metadata.
```python
store = FAISS(db_path="./vector_index")
loaded = store.load() # True if files exist
```
**Returns:** `True` if loaded successfully, `False` if files are missing.
**Raises:** `RuntimeError` if files exist but cannot be read.
---
### Properties
| Property | Type | Description |
|----------|------|-------------|
| `size` | `int` | Number of vectors in the index |
| `len(store)` | `int` | Same as `size` |
---
## Example: End-to-End
```python
import cv2
from uniface.detection import RetinaFace
from uniface.recognition import ArcFace
from uniface.stores import FAISS
detector = RetinaFace()
recognizer = ArcFace()
# Build
store = FAISS(db_path="./my_index")
image = cv2.imread("alice.jpg")
faces = detector.detect(image)
embedding = recognizer.get_normalized_embedding(image, faces[0].landmarks)
store.add(embedding, {"person_id": "alice"})
store.save()
# Search
store2 = FAISS(db_path="./my_index")
store2.load()
query = cv2.imread("unknown.jpg")
faces = detector.detect(query)
emb = recognizer.get_normalized_embedding(query, faces[0].landmarks)
result, sim = store2.search(emb)
if result:
print(f"Matched: {result['person_id']} (similarity: {sim:.3f})")
else:
print(f"No match (similarity: {sim:.3f})")
```
---
## See Also
- [Face Search Recipe](../recipes/face-search.md) - Building and querying indexes
- [Recognition Module](recognition.md) - Embedding extraction
- [Thresholds Guide](../concepts/thresholds-calibration.md) - Tuning similarity thresholds