Binary Quantization (BQ)

Added in v1.23

BQ is available for the flat index type from v1.23 onwards and for the hnsw index type from v1.24.

Binary quantization (BQ) is a vector compression technique that can reduce the size of a vector.

To use BQ, enable it as shown below and add data to the collection.

Additional information

• How to set the index type

Enable compression for new collection

BQ can be enabled at collection creation time through the collection definition:

Python Client v4

from weaviate.classes.config import Configure

client.collections.create(
    name="MyCollection",
    vector_config=Configure.Vectors.text2vec_openai(
        name="default",
        quantizer=Configure.VectorIndex.Quantizer.bq(),
    ),
)

  API docs

Python Client v3

class_definition = {
    "class": "MyCollection",
    "vectorizer": "text2vec-openai",  # Can be any vectorizer
    "vectorIndexType": "flat",
    "vectorIndexConfig": {
        "bq": {
            "enabled": True,
        },
    },
    #  Remainder not shown
}

client.schema.create_class(class_definition)

  API docs  Deprecated (v3)

JS/TS Client v3

import { configure } from 'weaviate-client';

const collection = await client.collections.create({
  name: 'MyCollection',
  vectorizers: weaviate.configure.vectors.selfProvided({
    vectorIndexConfig: weaviate.configure.vectorIndex.hnsw({
      quantizer: weaviate.configure.vectorIndex.quantizer.bq(),
    })
  })
})

  API docs

JS/TS Client v2

async function enableBQ() {
  const classObj = {
    class: 'MyCollection',
    vectorizer: 'text2vec-openai', // Can be any vectorizer
    vectorIndexType: 'flat',
    vectorIndexConfig: {
      bq: {
        enabled: true,
      },
    },
    //  Remainder not shown
  };
  const res = await client.schema.classCreator().withClass(classObj).do();
  console.log(res);
}

await enableBQ();

Go

// Define the configuration for BQ. Setting 'enabled' to true
bq_config := map[string]interface{}{
  "enabled": true,
}

// Define the class schema
class := &models.Class{
  Class:      className,
  Vectorizer: "text2vec-openai",
  // Assign the BQ configuration to the vector index config
  VectorIndexConfig: map[string]interface{}{
  	"bq": bq_config,
  },
}

// Create the collection in Weaviate
err = client.Schema().ClassCreator().
  WithClass(class).
  Do(context.Background())

  API docs

Java

WeaviateClass myCollection = WeaviateClass.builder()
    .className("MyCollection")
    .vectorizer("text2vec-openai")
    .vectorIndexConfig(VectorIndexConfig.builder()
        .bq(BQConfig.builder()
            .enabled(true)
            .build())
        .build())
    .properties(Arrays.asList(
        Property.builder()
            .name("title")
            .dataType(Arrays.asList(DataType.TEXT))
            .build()))
    .build();

Result<Boolean> createResult = client.schema().classCreator()
    .withClass(myCollection)
    .run();

  API docs

Enable compression for existing collection

Added in v1.31

The ability to enable BQ compression after collection creation was added in Weaviate v1.31.

BQ can also be enabled for an existing collection by updating the collection definition:

Python Client v4

from weaviate.classes.config import Reconfigure

collection = client.collections.get("MyCollection")
collection.config.update(
    vector_config=Reconfigure.Vectors.update(
        name="default",
        vector_index_config=Reconfigure.VectorIndex.flat(
            quantizer=Reconfigure.VectorIndex.Quantizer.bq(
                rescore_limit=20,
            ),
        ),
    )
)

  API docs

Go

// Get the existing collection configuration
class, err := client.Schema().ClassGetter().
  WithClassName(className).Do(context.Background())

if err != nil {
  log.Fatalf("get class for vec idx cfg update: %v", err)
}

// Get the current vector index configuration
cfg := class.VectorIndexConfig.(map[string]interface{})

// Add BQ configuration to enable binary quantization
cfg["bq"] = map[string]interface{}{
  "enabled":      true,
  "rescoreLimit": 200,
  "cache":        true,
}

// Update the class configuration
class.VectorIndexConfig = cfg

// Apply the updated configuration to the collection
err = client.Schema().ClassUpdater().
  WithClass(class).Do(context.Background())

if err != nil {
  log.Fatalf("update class to use bq: %v", err)
}

  API docs

Java

WeaviateClass updatedCollection = WeaviateClass.builder()
    .className("MyCollection")
    .description("Updated collection with BQ compression")
    .properties(Arrays.asList(
        Property.builder()
            .name("title")
            .dataType(Arrays.asList(DataType.TEXT))
            .build()))
    .vectorizer("text2vec-openai")
    .vectorIndexConfig(VectorIndexConfig.builder()
        .bq(BQConfig.builder()
            .enabled(true)
            .rescoreLimit(10L)
            .build())
        .build())
    .build();

Result<Boolean> updateResult = client.schema().classUpdater()
    .withClass(updatedCollection)
    .run();

  API docs

BQ parameters

The following parameters are available for BQ compression, under vectorIndexConfig:

Parameter	Type	Default	Details
bq : enabled	boolean	false	Enable BQ. Weaviate uses binary quantization (BQ) compression when true. The Python client v4 does not use the enabled parameter. To enable BQ with the v4 client, set a quantizer in the collection definition.
bq : rescoreLimit	integer	-1	The minimum number of candidates to fetch before rescoring.
bq : cache	boolean	false	Whether to use the vector cache.
vectorCacheMaxObjects	integer	1e12	Maximum number of objects in the memory cache. By default, this limit is set to one trillion (1e12) objects when a new collection is created. For sizing recommendations, see Vector cache considerations.

For example:

Python Client v4

from weaviate.classes.config import Configure

client.collections.create(
    name="MyCollection",
    vector_config=Configure.Vectors.text2vec_openai(
        name="default",
        quantizer=Configure.VectorIndex.Quantizer.bq(rescore_limit=200, cache=True),
        vector_index_config=Configure.VectorIndex.flat(
            vector_cache_max_objects=100000,
        ),
    ),
)

  API docs

Python Client v3

class_definition = {
    "class": "MyCollection",
    "vectorizer": "text2vec-openai",  # Can be any vectorizer
    "vectorIndexType": "flat",
    "vectorIndexConfig": {
        "bq": {
            "enabled": True,
            "rescoreLimit": 200,  # The minimum number of candidates to fetch before rescoring
            "cache": True,  # Default: False
        },
        "vectorCacheMaxObjects": 100000,  # Cache size (used if `cache` enabled)
    },
    # Remainder not shown
}

client.schema.create_class(class_definition)

  API docs  Deprecated (v3)

JS/TS Client v3

import { configure } from 'weaviate-client';

const collection = await client.collections.create({
  name: 'MyCollection',
  vectorizers: weaviate.configure.vectors.selfProvided({
    vectorIndexConfig: weaviate.configure.vectorIndex.hnsw({
      quantizer: weaviate.configure.vectorIndex.quantizer.bq({
        cache: true,     // Enable caching
        rescoreLimit: 200, // The minimum number of candidates to fetch before rescoring
      }),
      vectorCacheMaxObjects: 10000 // Cache size (used if `cache` enabled)
    })
  })
})

  API docs

JS/TS Client v2

async function bqWithOptions() {
  const classObj = {
    class: 'MyCollection',
    vectorizer: 'text2vec-openai', // Can be any vectorizer
    vectorIndexType: 'flat',
    vectorIndexConfig: {
      bq: {
        enabled: true,
        rescoreLimit: 200, // The minimum number of candidates to fetch before rescoring
        cache: true, // Default: false
      },
      vectorCacheMaxObjects: 100000, // Cache size (used if `cache` enabled)
    },
    //  Remainder not shown
  };
  const res = await client.schema.classCreator().withClass(classObj).do();
  console.log(res);
}

await bqWithOptions();

Go

// Define a custom configuration for BQ
bq_with_options_config := map[string]interface{}{
  "enabled":      true,
  "rescoreLimit": 200,  // The minimum number of candidates to fetch before rescoring
  "cache":        true, // Enable caching of binary quantized vectors
}

// Define the class schema with the custom BQ config and other HNSW settings
class_with_options := &models.Class{
  Class:      className,
  Vectorizer: "text2vec-openai",
  VectorIndexConfig: map[string]interface{}{
  	"bq": bq_with_options_config,
  	"distance":              "cosine", // Set the distance metric for HNSW
  	"vectorCacheMaxObjects": 100000,   // Configure the vector cache
  },
}

// Create the collection in Weaviate
err = client.Schema().ClassCreator().
  WithClass(class_with_options).
  Do(context.Background())

  API docs

Java

WeaviateClass myCollection = WeaviateClass.builder()
    .className("MyCollection")
    .vectorizer("text2vec-openai")
    .vectorIndexConfig(VectorIndexConfig.builder()
        .bq(BQConfig.builder()
            .enabled(true)
            .rescoreLimit(20L)
            .build())
        .build())
    .properties(Arrays.asList(
        Property.builder()
            .name("title")
            .dataType(Arrays.asList(DataType.TEXT))
            .build()))
    .build();

Result<Boolean> createResult = client.schema().classCreator()
    .withClass(myCollection)
    .run();

  API docs

Additional considerations

Multiple vector embeddings (named vectors)

Added in v1.24

Collections can have multiple named vectors. The vectors in a collection can have their own configurations, and compression must be enabled independently for each vector. Every vector is independent and can use PQ, BQ, RQ, SQ, or no compression.

Multi-vector embeddings (ColBERT, ColPali, etc.)

Added in v1.30

Multi-vector embeddings (implemented through models like ColBERT, ColPali, or ColQwen) represent each object or query using multiple vectors instead of a single vector. Just like with single vectors, multi-vectors support PQ, BQ, RQ, SQ, or no compression.

During the initial search phase, compressed vectors are used for efficiency. However, when computing the MaxSim operation, uncompressed vectors are utilized to ensure more precise similarity calculations. This approach balances the benefits of compression for search efficiency with the accuracy of uncompressed vectors during final scoring.

Further resources

• Starter guides: Compression
• Reference: Vector index
• Concepts: Vector quantization
• Concepts: Vector index

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