Qdrant 中的大规模搜索

export QDRANT_URL="https://xxxx-xxxx.xxxx.cloud.qdrant.io"
export QDRANT_API_KEY="xxxx-xxxx-xxxx-xxxx"

python upload.py

client.create_collection(
        QDRANT_COLLECTION_NAME,
        vectors_config=models.VectorParams(
            size=512, # CLIP model output size
            distance=models.Distance.COSINE, # CLIP model uses cosine distance
            datatype=models.Datatype.FLOAT16, # We only need 16 bits for float, otherwise disk usage would be 800Gb instead of 400Gb
            on_disk=True # We don't need original vectors in RAM
        ),
        # Even though CLIP vectors don't work well with binary quantization, out of the box,
        # we can rely on query-time oversampling to get more accurate results
        quantization_config=models.BinaryQuantization(
            binary=models.BinaryQuantizationConfig(
                always_ram=True,
            )
        ),
        optimizers_config=models.OptimizersConfigDiff(
            # Bigger size of segments are desired for faster search
            # However it might be slower for indexing
            max_segment_size=5_000_000, 
        ),
        # Having larger M value is desirable for higher accuracy,
        # but in our case we care more about memory usage
        # We could still achieve reasonable accuracy even with M=6 + oversampling
        hnsw_config=models.HnswConfigDiff(
            m=6, # decrease M for lower memory usage
            on_disk=False
        ),
    )

400_000_000 * 512d / 8 bits / 1024 (Kb) / 1024 (Mb) / 1024 (Gb) = 23.84Gb

400_000_000 * (6 * 2) * 4 bytes / 1024 (Kb) / 1024 (Mb) / 1024 (Gb) = 17.881Gb

// This is s simplified version of the IdTracker struct
// It omits all optimizations and small details,
// but gives a good estimation of memory usage
IdTracker {
    // Mapping of internal id to version (u64), compressed to 4 bytes
    // Required for versioning and conflict resolution between segments
    internal_to_version, // 400M x 4 = 1.5Gb

    // Mapping of external id to internal id, 4 bytes per point.
    // Required to determine original point ID after search inside the segment
    internal_to_external: Vec<u128>, // 400M x 16 = 6.4Gb

    // Mapping of external id to internal id. For numeric ids it uses 8 bytes,
    //  UUIDs are stored as 16 bytes.
    // Required to determine sequential point ID inside the segment
    external_to_internal: Vec<u64, u32>, // 400M x (8 + 4) = 4.5Gb
}

limit = 50
rescore_limit = 1000 # oversampling factor is 20

query = vectors[query_id] # One of existing vectors

response = client.query_points(
        collection_name=QDRANT_COLLECTION_NAME,
        query=query,
        limit=limit,
        # Go to disk 
        search_params=models.SearchParams(
            quantization=models.QuantizationSearchParams(
                rescore=True,
            ),
        ),
        # Prefetch is performed using only in-RAM data,
        # so querying even large amount of data is fast
        prefetch=models.Prefetch(
            query=query,
            limit=rescore_limit,
            params=models.SearchParams(
                quantization=models.QuantizationSearchParams(
                    # Avoid rescoring in prefetch
                    # We should do it explicitly on the second stage
                    rescore=False,
                ),
            )
        )
    )

QDRANT__STORAGE__PERFORMANCE__ASYNC_SCORER=true

storage:
  performance:
    async_scorer: true

python eval.py --rescore_limit 1000