from __future__ import annotations import typing import uuid from typing import ( Any, Callable, Dict, Iterable, List, Optional, Tuple, Type, TypeVar, Union, ) import numpy as np if typing.TYPE_CHECKING: from cassandra.cluster import Session from langchain_core.documents import Document from langchain_core.embeddings import Embeddings from langchain_core.vectorstores import VectorStore from langchain_community.vectorstores.utils import maximal_marginal_relevance CVST = TypeVar("CVST", bound="Cassandra") class Cassandra(VectorStore): """Wrapper around Apache Cassandra(R) for vector-store workloads. To use it, you need a recent installation of the `cassio` library and a Cassandra cluster / Astra DB instance supporting vector capabilities. Visit the cassio.org website for extensive quickstarts and code examples. Example: .. code-block:: python from langchain_community.vectorstores import Cassandra from langchain_community.embeddings.openai import OpenAIEmbeddings embeddings = OpenAIEmbeddings() session = ... # create your Cassandra session object keyspace = 'my_keyspace' # the keyspace should exist already table_name = 'my_vector_store' vectorstore = Cassandra(embeddings, session, keyspace, table_name) """ _embedding_dimension: Union[int, None] @staticmethod def _filter_to_metadata(filter_dict: Optional[Dict[str, str]]) -> Dict[str, Any]: if filter_dict is None: return {} else: return filter_dict def _get_embedding_dimension(self) -> int: if self._embedding_dimension is None: self._embedding_dimension = len( self.embedding.embed_query("This is a sample sentence.") ) return self._embedding_dimension def __init__( self, embedding: Embeddings, session: Session, keyspace: str, table_name: str, ttl_seconds: Optional[int] = None, ) -> None: try: from cassio.table import MetadataVectorCassandraTable except (ImportError, ModuleNotFoundError): raise ImportError( "Could not import cassio python package. " "Please install it with `pip install cassio`." ) """Create a vector table.""" self.embedding = embedding self.session = session self.keyspace = keyspace self.table_name = table_name self.ttl_seconds = ttl_seconds # self._embedding_dimension = None # self.table = MetadataVectorCassandraTable( session=session, keyspace=keyspace, table=table_name, vector_dimension=self._get_embedding_dimension(), metadata_indexing="all", primary_key_type="TEXT", ) @property def embeddings(self) -> Embeddings: return self.embedding @staticmethod def _dont_flip_the_cos_score(distance: float) -> float: # the identity return distance def _select_relevance_score_fn(self) -> Callable[[float], float]: """ The underlying VectorTable already returns a "score proper", i.e. one in [0, 1] where higher means more *similar*, so here the final score transformation is not reversing the interval: """ return self._dont_flip_the_cos_score def delete_collection(self) -> None: """ Just an alias for `clear` (to better align with other VectorStore implementations). """ self.clear() def clear(self) -> None: """Empty the collection.""" self.table.clear() def delete_by_document_id(self, document_id: str) -> None: return self.table.delete(row_id=document_id) def delete(self, ids: Optional[List[str]] = None, **kwargs: Any) -> Optional[bool]: """Delete by vector IDs. Args: ids: List of ids to delete. Returns: Optional[bool]: True if deletion is successful, False otherwise, None if not implemented. """ if ids is None: raise ValueError("No ids provided to delete.") for document_id in ids: self.delete_by_document_id(document_id) return True def add_texts( self, texts: Iterable[str], metadatas: Optional[List[dict]] = None, ids: Optional[List[str]] = None, batch_size: int = 16, ttl_seconds: Optional[int] = None, **kwargs: Any, ) -> List[str]: """Run more texts through the embeddings and add to the vectorstore. Args: texts (Iterable[str]): Texts to add to the vectorstore. metadatas (Optional[List[dict]], optional): Optional list of metadatas. ids (Optional[List[str]], optional): Optional list of IDs. batch_size (int): Number of concurrent requests to send to the server. ttl_seconds (Optional[int], optional): Optional time-to-live for the added texts. Returns: List[str]: List of IDs of the added texts. """ _texts = list(texts) # lest it be a generator or something if ids is None: ids = [uuid.uuid4().hex for _ in _texts] if metadatas is None: metadatas = [{} for _ in _texts] # ttl_seconds = ttl_seconds or self.ttl_seconds # embedding_vectors = self.embedding.embed_documents(_texts) # for i in range(0, len(_texts), batch_size): batch_texts = _texts[i : i + batch_size] batch_embedding_vectors = embedding_vectors[i : i + batch_size] batch_ids = ids[i : i + batch_size] batch_metadatas = metadatas[i : i + batch_size] futures = [ self.table.put_async( row_id=text_id, body_blob=text, vector=embedding_vector, metadata=metadata or {}, ttl_seconds=ttl_seconds, ) for text, embedding_vector, text_id, metadata in zip( batch_texts, batch_embedding_vectors, batch_ids, batch_metadatas ) ] for future in futures: future.result() return ids # id-returning search facilities def similarity_search_with_score_id_by_vector( self, embedding: List[float], k: int = 4, filter: Optional[Dict[str, str]] = None, ) -> List[Tuple[Document, float, str]]: """Return docs most similar to embedding vector. Args: embedding (str): Embedding to look up documents similar to. k (int): Number of Documents to return. Defaults to 4. Returns: List of (Document, score, id), the most similar to the query vector. """ search_metadata = self._filter_to_metadata(filter) # hits = self.table.metric_ann_search( vector=embedding, n=k, metric="cos", metadata=search_metadata, ) # We stick to 'cos' distance as it can be normalized on a 0-1 axis # (1=most relevant), as required by this class' contract. return [ ( Document( page_content=hit["body_blob"], metadata=hit["metadata"], ), 0.5 + 0.5 * hit["distance"], hit["row_id"], ) for hit in hits ] def similarity_search_with_score_id( self, query: str, k: int = 4, filter: Optional[Dict[str, str]] = None, ) -> List[Tuple[Document, float, str]]: embedding_vector = self.embedding.embed_query(query) return self.similarity_search_with_score_id_by_vector( embedding=embedding_vector, k=k, filter=filter, ) # id-unaware search facilities def similarity_search_with_score_by_vector( self, embedding: List[float], k: int = 4, filter: Optional[Dict[str, str]] = None, ) -> List[Tuple[Document, float]]: """Return docs most similar to embedding vector. Args: embedding (str): Embedding to look up documents similar to. k (int): Number of Documents to return. Defaults to 4. Returns: List of (Document, score), the most similar to the query vector. """ return [ (doc, score) for (doc, score, docId) in self.similarity_search_with_score_id_by_vector( embedding=embedding, k=k, filter=filter, ) ] def similarity_search( self, query: str, k: int = 4, filter: Optional[Dict[str, str]] = None, **kwargs: Any, ) -> List[Document]: embedding_vector = self.embedding.embed_query(query) return self.similarity_search_by_vector( embedding_vector, k, filter=filter, ) def similarity_search_by_vector( self, embedding: List[float], k: int = 4, filter: Optional[Dict[str, str]] = None, **kwargs: Any, ) -> List[Document]: return [ doc for doc, _ in self.similarity_search_with_score_by_vector( embedding, k, filter=filter, ) ] def similarity_search_with_score( self, query: str, k: int = 4, filter: Optional[Dict[str, str]] = None, ) -> List[Tuple[Document, float]]: embedding_vector = self.embedding.embed_query(query) return self.similarity_search_with_score_by_vector( embedding_vector, k, filter=filter, ) def max_marginal_relevance_search_by_vector( self, embedding: List[float], k: int = 4, fetch_k: int = 20, lambda_mult: float = 0.5, filter: Optional[Dict[str, str]] = None, **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. 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. Returns: List of Documents selected by maximal marginal relevance. """ search_metadata = self._filter_to_metadata(filter) prefetch_hits = list( self.table.metric_ann_search( vector=embedding, n=fetch_k, metric="cos", metadata=search_metadata, ) ) # let the mmr utility pick the *indices* in the above array mmr_chosen_indices = maximal_marginal_relevance( np.array(embedding, dtype=np.float32), [pf_hit["vector"] for pf_hit in prefetch_hits], k=k, lambda_mult=lambda_mult, ) mmr_hits = [ pf_hit for pf_index, pf_hit in enumerate(prefetch_hits) if pf_index in mmr_chosen_indices ] return [ Document( page_content=hit["body_blob"], metadata=hit["metadata"], ) for hit in mmr_hits ] def max_marginal_relevance_search( self, query: str, k: int = 4, fetch_k: int = 20, lambda_mult: float = 0.5, filter: Optional[Dict[str, str]] = None, **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. 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. Optional. Returns: List of Documents selected by maximal marginal relevance. """ embedding_vector = self.embedding.embed_query(query) return self.max_marginal_relevance_search_by_vector( embedding_vector, k, fetch_k, lambda_mult=lambda_mult, filter=filter, ) @classmethod def from_texts( cls: Type[CVST], texts: List[str], embedding: Embeddings, metadatas: Optional[List[dict]] = None, batch_size: int = 16, **kwargs: Any, ) -> CVST: """Create a Cassandra vectorstore from raw texts. No support for specifying text IDs Returns: a Cassandra vectorstore. """ session: Session = kwargs["session"] keyspace: str = kwargs["keyspace"] table_name: str = kwargs["table_name"] cassandraStore = cls( embedding=embedding, session=session, keyspace=keyspace, table_name=table_name, ) cassandraStore.add_texts(texts=texts, metadatas=metadatas) return cassandraStore @classmethod def from_documents( cls: Type[CVST], documents: List[Document], embedding: Embeddings, batch_size: int = 16, **kwargs: Any, ) -> CVST: """Create a Cassandra vectorstore from a document list. No support for specifying text IDs Returns: a Cassandra vectorstore. """ texts = [doc.page_content for doc in documents] metadatas = [doc.metadata for doc in documents] session: Session = kwargs["session"] keyspace: str = kwargs["keyspace"] table_name: str = kwargs["table_name"] return cls.from_texts( texts=texts, metadatas=metadatas, embedding=embedding, session=session, keyspace=keyspace, table_name=table_name, )