How to Index Vector Fields

vector

Required

Human-readable label that identifies this field type. Value must be vector.

Int

Required

Number of vector dimensions that MongoDB Search enforces at index-time and query-time. You can set this field only for vector-type fields. You must specify a value less than or equal to 8192.

For indexing quantized vectors or BinData, you can specify one of the following values:

• 1 to 8192 for int8 vectors for ingestion.

• Multiple of 8 for int1 vectors for ingestion.

• 1 to 8192 for binData(float32) and array(float32) vectors for automatic scalar quantization.

• Multiple of 8 for binData(float32) and array(float32) vectors for automatic binary quantization.

The embedding model you choose determines the number of dimensions in your vector embeddings, with some models having multiple options for how many dimensions are output. To learn more, see Choosing a Method to Create Embeddings.

String

Required

Vector similarity function to use to search for top K-nearest neighbors. You can set this field only for vector-type fields.

You can specify one of the following values:

• euclidean - measures the distance between ends of vectors.

• cosine - measures similarity based on the angle between vectors.

• dotProduct - measures similarity like cosine, but takes into account the magnitude of the vector.

To learn more, see About the Similarity Functions.

String

Optional

Type of automatic vector quantization for your vectors. Use this setting only if your embeddings are float or double vectors.

You can specify one of the following values:

• none - Indicates no automatic quantization for the vector embeddings. Use this setting if you have pre-quantized vectors for ingestion. If omitted, this is the default value.

• scalar - Indicates scalar quantization, which transforms values to 1 byte integers.

• binary - Indicates binary quantization, which transforms values to a single bit. To use this value, numDimensions must be a multiple of 8.

  If precision is critical, select none or scalar instead of binary.

To learn more, see Vector Quantization.

Object

Optional

Parameters to use for Hierarchical Navigable Small Worlds graph construction. If omitted, uses the default values for the maxEdges and numEdgeCandidates parameters.

IMPORTANT: This is available as a Preview feature. Modifying the default values might negatively impact your MongoDB Search index and queries.

Int

Optional

Maximum number of edges (or connections) that a node can have in the Hierarchical Navigable Small Worlds graph. Value can be between 16 and 64, both inclusive. If omitted, defaults to 16. For example, for a value of 16, each node can have a maximum of sixteen outgoing edges at each layer of the Hierarchical Navigable Small Worlds graph.

A higher number improves recall (accuracy of search results) because the graph is better connected. However, this also increases query and indexing time by increasing the number of neighbors to evaluate per graph node, and requires more memory to store the additional nodes for each connection in the Hierarchical Navigable Small Worlds graph.

Int

Optional

Analogous to numCandidates at query-time, this parameter controls the maximum number of nodes to evaluate to find the closest neighbors to connect to a new node. Value can be between 100 and 3200, both inclusive. If omitted, defaults to 100.

A higher number provides a graph with high-quality connections, which can improve search quality (recall), but it can also increase query latency.