langchain/libs/community/langchain_community/vectorstores/utils.py

"""Utility functions for working with vectors and vectorstores."""

from enum import Enum
from typing import List, Tuple, Type

import numpy as np
from langchain_core.documents import Document

from langchain_community.utils.math import cosine_similarity


class DistanceStrategy(str, Enum):
    """Enumerator of the Distance strategies for calculating distances
    between vectors."""

    EUCLIDEAN_DISTANCE = "EUCLIDEAN_DISTANCE"
    MAX_INNER_PRODUCT = "MAX_INNER_PRODUCT"
    DOT_PRODUCT = "DOT_PRODUCT"
    JACCARD = "JACCARD"
    COSINE = "COSINE"


def maximal_marginal_relevance(
    query_embedding: np.ndarray,
    embedding_list: list,
    lambda_mult: float = 0.5,
    k: int = 4,
) -> List[int]:
    """Calculate maximal marginal relevance."""
    if min(k, len(embedding_list)) <= 0:
        return []
    if query_embedding.ndim == 1:
        query_embedding = np.expand_dims(query_embedding, axis=0)
    similarity_to_query = cosine_similarity(query_embedding, embedding_list)[0]
    most_similar = int(np.argmax(similarity_to_query))
    idxs = [most_similar]
    selected = np.array([embedding_list[most_similar]])
    while len(idxs) < min(k, len(embedding_list)):
        best_score = -np.inf
        idx_to_add = -1
        similarity_to_selected = cosine_similarity(embedding_list, selected)
        for i, query_score in enumerate(similarity_to_query):
            if i in idxs:
                continue
            redundant_score = max(similarity_to_selected[i])
            equation_score = (
                lambda_mult * query_score - (1 - lambda_mult) * redundant_score
            )
            if equation_score > best_score:
                best_score = equation_score
                idx_to_add = i
        idxs.append(idx_to_add)
        selected = np.append(selected, [embedding_list[idx_to_add]], axis=0)
    return idxs


def filter_complex_metadata(
    documents: List[Document],
    *,
    allowed_types: Tuple[Type, ...] = (str, bool, int, float),
) -> List[Document]:
    """Filter out metadata types that are not supported for a vector store."""
    updated_documents = []
    for document in documents:
        filtered_metadata = {}
        for key, value in document.metadata.items():
            if not isinstance(value, allowed_types):
                continue
            filtered_metadata[key] = value

        document.metadata = filtered_metadata
        updated_documents.append(document)

    return updated_documents