Source code for langchain.vectorstores.faiss
"""Wrapper around FAISS vector database."""
from __future__ import annotations
import math
import os
import pickle
import uuid
from pathlib import Path
from typing import Any, Callable, Dict, Iterable, List, Optional, Tuple
import numpy as np
from langchain.docstore.base import AddableMixin, Docstore
from langchain.docstore.document import Document
from langchain.docstore.in_memory import InMemoryDocstore
from langchain.embeddings.base import Embeddings
from langchain.vectorstores.base import VectorStore
from langchain.vectorstores.utils import maximal_marginal_relevance
def dependable_faiss_import(no_avx2: Optional[bool] = None) -> Any:
    """
    Import faiss if available, otherwise raise error.
    If FAISS_NO_AVX2 environment variable is set, it will be considered
    to load FAISS with no AVX2 optimization.
    Args:
        no_avx2: Load FAISS strictly with no AVX2 optimization
            so that the vectorstore is portable and compatible with other devices.
    """
    if no_avx2 is None and "FAISS_NO_AVX2" in os.environ:
        no_avx2 = bool(os.getenv("FAISS_NO_AVX2"))
    try:
        if no_avx2:
            from faiss import swigfaiss as faiss
        else:
            import faiss
    except ImportError:
        raise ValueError(
            "Could not import faiss python package. "
            "Please install it with `pip install faiss` "
            "or `pip install faiss-cpu` (depending on Python version)."
        )
    return faiss
def _default_relevance_score_fn(score: float) -> float:
return faiss
def _default_relevance_score_fn(score: float) -> float:
    """Return a similarity score on a scale [0, 1]."""
    # The 'correct' relevance function
    # may differ depending on a few things, including:
    # - the distance / similarity metric used by the VectorStore
    # - the scale of your embeddings (OpenAI's are unit normed. Many others are not!)
    # - embedding dimensionality
    # - etc.
    # This function converts the euclidean norm of normalized embeddings
    # (0 is most similar, sqrt(2) most dissimilar)
    # to a similarity function (0 to 1)
    return 1.0 - score / math.sqrt(2)
[docs]class FAISS(VectorStore):
    """Wrapper around FAISS vector database.
    To use, you should have the ``faiss`` python package installed.
    Example:
        .. code-block:: python
            from langchain import FAISS
            faiss = FAISS(embedding_function, index, docstore, index_to_docstore_id)
    """
    def __init__(
        self,
        embedding_function: Callable,
        index: Any,
        docstore: Docstore,
        index_to_docstore_id: Dict[int, str],
        relevance_score_fn: Optional[
            Callable[[float], float]
        ] = _default_relevance_score_fn,
        normalize_L2: bool = False,
    ):
        """Initialize with necessary components."""
        self.embedding_function = embedding_function
        self.index = index
        self.docstore = docstore
        self.index_to_docstore_id = index_to_docstore_id
        self.relevance_score_fn = relevance_score_fn
        self._normalize_L2 = normalize_L2
self._normalize_L2 = normalize_L2
    def __add(
        self,
        texts: Iterable[str],
        embeddings: Iterable[List[float]],
        metadatas: Optional[List[dict]] = None,
        ids: Optional[List[str]] = None,
        **kwargs: Any,
    ) -> List[str]:
        if not isinstance(self.docstore, AddableMixin):
            raise ValueError(
                "If trying to add texts, the underlying docstore should support "
                f"adding items, which {self.docstore} does not"
            )
        documents = []
        for i, text in enumerate(texts):
            metadata = metadatas[i] if metadatas else {}
            documents.append(Document(page_content=text, metadata=metadata))
        if ids is None:
            ids = [str(uuid.uuid4()) for _ in texts]
        # Add to the index, the index_to_id mapping, and the docstore.
        starting_len = len(self.index_to_docstore_id)
        faiss = dependable_faiss_import()
        vector = np.array(embeddings, dtype=np.float32)
        if self._normalize_L2:
            faiss.normalize_L2(vector)
        self.index.add(vector)
        # Get list of index, id, and docs.
        full_info = [(starting_len + i, ids[i], doc) for i, doc in enumerate(documents)]
        # Add information to docstore and index.
        self.docstore.add({_id: doc for _, _id, doc in full_info})
        index_to_id = {index: _id for index, _id, _ in full_info}
        self.index_to_docstore_id.update(index_to_id)
        return [_id for _, _id, _ in full_info]
return [_id for _, _id, _ in full_info]
[docs]    def add_texts(
        self,
        texts: Iterable[str],
        metadatas: Optional[List[dict]] = None,
        ids: Optional[List[str]] = None,
        **kwargs: Any,
    ) -> List[str]:
        """Run more texts through the embeddings and add to the vectorstore.
        Args:
            texts: Iterable of strings to add to the vectorstore.
            metadatas: Optional list of metadatas associated with the texts.
            ids: Optional list of unique IDs.
        Returns:
            List of ids from adding the texts into the vectorstore.
        """
        if not isinstance(self.docstore, AddableMixin):
            raise ValueError(
                "If trying to add texts, the underlying docstore should support "
                f"adding items, which {self.docstore} does not"
            )
        # Embed and create the documents.
        embeddings = [self.embedding_function(text) for text in texts]
        return self.__add(texts, embeddings, metadatas=metadatas, ids=ids, **kwargs)
[docs]    def add_embeddings(
        self,
        text_embeddings: Iterable[Tuple[str, List[float]]],
        metadatas: Optional[List[dict]] = None,
        ids: Optional[List[str]] = None,
        **kwargs: Any,
    ) -> List[str]:
        """Run more texts through the embeddings and add to the vectorstore.
        Args:
            text_embeddings: Iterable pairs of string and embedding to
                add to the vectorstore.
            metadatas: Optional list of metadatas associated with the texts.
            ids: Optional list of unique IDs.
        Returns:
ids: Optional list of unique IDs.
        Returns:
            List of ids from adding the texts into the vectorstore.
        """
        if not isinstance(self.docstore, AddableMixin):
            raise ValueError(
                "If trying to add texts, the underlying docstore should support "
                f"adding items, which {self.docstore} does not"
            )
        # Embed and create the documents.
        texts = [te[0] for te in text_embeddings]
        embeddings = [te[1] for te in text_embeddings]
        return self.__add(texts, embeddings, metadatas=metadatas, ids=ids, **kwargs)
[docs]    def similarity_search_with_score_by_vector(
        self, embedding: List[float], k: int = 4
    ) -> List[Tuple[Document, float]]:
        """Return docs most similar to query.
        Args:
            embedding: Embedding vector to look up documents similar to.
            k: Number of Documents to return. Defaults to 4.
        Returns:
            List of Documents most similar to the query and score for each
        """
        faiss = dependable_faiss_import()
        vector = np.array([embedding], dtype=np.float32)
        if self._normalize_L2:
            faiss.normalize_L2(vector)
        scores, indices = self.index.search(vector, k)
        docs = []
        for j, i in enumerate(indices[0]):
            if i == -1:
                # This happens when not enough docs are returned.
                continue
            _id = self.index_to_docstore_id[i]
            doc = self.docstore.search(_id)
            if not isinstance(doc, Document):
                raise ValueError(f"Could not find document for id {_id}, got {doc}")
raise ValueError(f"Could not find document for id {_id}, got {doc}")
            docs.append((doc, scores[0][j]))
        return docs
[docs]    def similarity_search_with_score(
        self, query: str, k: int = 4
    ) -> List[Tuple[Document, float]]:
        """Return docs most similar to query.
        Args:
            query: Text to look up documents similar to.
            k: Number of Documents to return. Defaults to 4.
        Returns:
            List of Documents most similar to the query and score for each
        """
        embedding = self.embedding_function(query)
        docs = self.similarity_search_with_score_by_vector(embedding, k)
        return docs
[docs]    def similarity_search_by_vector(
        self, embedding: List[float], k: int = 4, **kwargs: Any
    ) -> List[Document]:
        """Return docs most similar to embedding vector.
        Args:
            embedding: Embedding to look up documents similar to.
            k: Number of Documents to return. Defaults to 4.
        Returns:
            List of Documents most similar to the embedding.
        """
        docs_and_scores = self.similarity_search_with_score_by_vector(embedding, k)
        return [doc for doc, _ in docs_and_scores]
[docs]    def similarity_search(
        self, query: str, k: int = 4, **kwargs: Any
    ) -> List[Document]:
        """Return docs most similar to query.
        Args:
            query: Text to look up documents similar to.
            k: Number of Documents to return. Defaults to 4.
        Returns:
            List of Documents most similar to the query.
        """
Returns:
            List of Documents most similar to the query.
        """
        docs_and_scores = self.similarity_search_with_score(query, k)
        return [doc for doc, _ in docs_and_scores]
[docs]    def max_marginal_relevance_search_by_vector(
        self,
        embedding: List[float],
        k: int = 4,
        fetch_k: int = 20,
        lambda_mult: float = 0.5,
        **kwargs: Any,
    ) -> List[Document]:
        """Return docs selected using the maximal marginal relevance.
        Maximal marginal relevance optimizes for similarity to query AND diversity
        among selected documents.
        Args:
            embedding: Embedding to look up documents similar to.
            k: Number of Documents to return. Defaults to 4.
            fetch_k: Number of Documents to fetch to pass to MMR algorithm.
            lambda_mult: Number between 0 and 1 that determines the degree
                        of diversity among the results with 0 corresponding
                        to maximum diversity and 1 to minimum diversity.
                        Defaults to 0.5.
        Returns:
            List of Documents selected by maximal marginal relevance.
        """
        _, indices = self.index.search(np.array([embedding], dtype=np.float32), fetch_k)
        # -1 happens when not enough docs are returned.
        embeddings = [self.index.reconstruct(int(i)) for i in indices[0] if i != -1]
        mmr_selected = maximal_marginal_relevance(
            np.array([embedding], dtype=np.float32),
            embeddings,
            k=k,
            lambda_mult=lambda_mult,
        )
        selected_indices = [indices[0][i] for i in mmr_selected]
        docs = []
docs = []
        for i in selected_indices:
            if i == -1:
                # This happens when not enough docs are returned.
                continue
            _id = self.index_to_docstore_id[i]
            doc = self.docstore.search(_id)
            if not isinstance(doc, Document):
                raise ValueError(f"Could not find document for id {_id}, got {doc}")
            docs.append(doc)
        return docs
[docs]    def max_marginal_relevance_search(
        self,
        query: str,
        k: int = 4,
        fetch_k: int = 20,
        lambda_mult: float = 0.5,
        **kwargs: Any,
    ) -> List[Document]:
        """Return docs selected using the maximal marginal relevance.
        Maximal marginal relevance optimizes for similarity to query AND diversity
        among selected documents.
        Args:
            query: Text to look up documents similar to.
            k: Number of Documents to return. Defaults to 4.
            fetch_k: Number of Documents to fetch to pass to MMR algorithm.
            lambda_mult: Number between 0 and 1 that determines the degree
                        of diversity among the results with 0 corresponding
                        to maximum diversity and 1 to minimum diversity.
                        Defaults to 0.5.
        Returns:
            List of Documents selected by maximal marginal relevance.
        """
        embedding = self.embedding_function(query)
        docs = self.max_marginal_relevance_search_by_vector(
            embedding, k, fetch_k, lambda_mult=lambda_mult
        )
        return docs
[docs]    def merge_from(self, target: FAISS) -> None:
        """Merge another FAISS object with the current one.
        Add the target FAISS to the current one.
Add the target FAISS to the current one.
        Args:
            target: FAISS object you wish to merge into the current one
        Returns:
            None.
        """
        if not isinstance(self.docstore, AddableMixin):
            raise ValueError("Cannot merge with this type of docstore")
        # Numerical index for target docs are incremental on existing ones
        starting_len = len(self.index_to_docstore_id)
        # Merge two IndexFlatL2
        self.index.merge_from(target.index)
        # Get id and docs from target FAISS object
        full_info = []
        for i, target_id in target.index_to_docstore_id.items():
            doc = target.docstore.search(target_id)
            if not isinstance(doc, Document):
                raise ValueError("Document should be returned")
            full_info.append((starting_len + i, target_id, doc))
        # Add information to docstore and index_to_docstore_id.
        self.docstore.add({_id: doc for _, _id, doc in full_info})
        index_to_id = {index: _id for index, _id, _ in full_info}
        self.index_to_docstore_id.update(index_to_id)
    @classmethod
    def __from(
        cls,
        texts: List[str],
        embeddings: List[List[float]],
        embedding: Embeddings,
        metadatas: Optional[List[dict]] = None,
        ids: Optional[List[str]] = None,
        normalize_L2: bool = False,
        **kwargs: Any,
    ) -> FAISS:
        faiss = dependable_faiss_import()
        index = faiss.IndexFlatL2(len(embeddings[0]))
        vector = np.array(embeddings, dtype=np.float32)
        if normalize_L2:
vector = np.array(embeddings, dtype=np.float32)
        if normalize_L2:
            faiss.normalize_L2(vector)
        index.add(vector)
        documents = []
        if ids is None:
            ids = [str(uuid.uuid4()) for _ in texts]
        for i, text in enumerate(texts):
            metadata = metadatas[i] if metadatas else {}
            documents.append(Document(page_content=text, metadata=metadata))
        index_to_id = dict(enumerate(ids))
        docstore = InMemoryDocstore(dict(zip(index_to_id.values(), documents)))
        return cls(
            embedding.embed_query,
            index,
            docstore,
            index_to_id,
            normalize_L2=normalize_L2,
            **kwargs,
        )
[docs]    @classmethod
    def from_texts(
        cls,
        texts: List[str],
        embedding: Embeddings,
        metadatas: Optional[List[dict]] = None,
        ids: Optional[List[str]] = None,
        **kwargs: Any,
    ) -> FAISS:
        """Construct FAISS wrapper from raw documents.
        This is a user friendly interface that:
            1. Embeds documents.
            2. Creates an in memory docstore
            3. Initializes the FAISS database
        This is intended to be a quick way to get started.
        Example:
            .. code-block:: python
                from langchain import FAISS
                from langchain.embeddings import OpenAIEmbeddings
                embeddings = OpenAIEmbeddings()
                faiss = FAISS.from_texts(texts, embeddings)
        """
        embeddings = embedding.embed_documents(texts)
        return cls.__from(
            texts,
            embeddings,
            embedding,
return cls.__from(
            texts,
            embeddings,
            embedding,
            metadatas=metadatas,
            ids=ids,
            **kwargs,
        )
[docs]    @classmethod
    def from_embeddings(
        cls,
        text_embeddings: List[Tuple[str, List[float]]],
        embedding: Embeddings,
        metadatas: Optional[List[dict]] = None,
        ids: Optional[List[str]] = None,
        **kwargs: Any,
    ) -> FAISS:
        """Construct FAISS wrapper from raw documents.
        This is a user friendly interface that:
            1. Embeds documents.
            2. Creates an in memory docstore
            3. Initializes the FAISS database
        This is intended to be a quick way to get started.
        Example:
            .. code-block:: python
                from langchain import FAISS
                from langchain.embeddings import OpenAIEmbeddings
                embeddings = OpenAIEmbeddings()
                text_embeddings = embeddings.embed_documents(texts)
                text_embedding_pairs = list(zip(texts, text_embeddings))
                faiss = FAISS.from_embeddings(text_embedding_pairs, embeddings)
        """
        texts = [t[0] for t in text_embeddings]
        embeddings = [t[1] for t in text_embeddings]
        return cls.__from(
            texts,
            embeddings,
            embedding,
            metadatas=metadatas,
            ids=ids,
            **kwargs,
        )
[docs]    def save_local(self, folder_path: str, index_name: str = "index") -> None:
        """Save FAISS index, docstore, and index_to_docstore_id to disk.
        Args:
Args:
            folder_path: folder path to save index, docstore,
                and index_to_docstore_id to.
            index_name: for saving with a specific index file name
        """
        path = Path(folder_path)
        path.mkdir(exist_ok=True, parents=True)
        # save index separately since it is not picklable
        faiss = dependable_faiss_import()
        faiss.write_index(
            self.index, str(path / "{index_name}.faiss".format(index_name=index_name))
        )
        # save docstore and index_to_docstore_id
        with open(path / "{index_name}.pkl".format(index_name=index_name), "wb") as f:
            pickle.dump((self.docstore, self.index_to_docstore_id), f)
[docs]    @classmethod
    def load_local(
        cls, folder_path: str, embeddings: Embeddings, index_name: str = "index"
    ) -> FAISS:
        """Load FAISS index, docstore, and index_to_docstore_id to disk.
        Args:
            folder_path: folder path to load index, docstore,
                and index_to_docstore_id from.
            embeddings: Embeddings to use when generating queries
            index_name: for saving with a specific index file name
        """
        path = Path(folder_path)
        # load index separately since it is not picklable
        faiss = dependable_faiss_import()
        index = faiss.read_index(
            str(path / "{index_name}.faiss".format(index_name=index_name))
        )
        # load docstore and index_to_docstore_id
        with open(path / "{index_name}.pkl".format(index_name=index_name), "rb") as f:
docstore, index_to_docstore_id = pickle.load(f)
        return cls(embeddings.embed_query, index, docstore, index_to_docstore_id)
    def _similarity_search_with_relevance_scores(
        self,
        query: str,
        k: int = 4,
        **kwargs: Any,
    ) -> List[Tuple[Document, float]]:
        """Return docs and their similarity scores on a scale from 0 to 1."""
        if self.relevance_score_fn is None:
            raise ValueError(
                "normalize_score_fn must be provided to"
                " FAISS constructor to normalize scores"
            )
        docs_and_scores = self.similarity_search_with_score(query, k=k)
        return [(doc, self.relevance_score_fn(score)) for doc, score in docs_and_scores]
By Harrison Chase