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556 lines
20 KiB
Python
556 lines
20 KiB
Python
"""Wrapper around Elasticsearch vector database."""
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from __future__ import annotations
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import uuid
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from abc import ABC
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from typing import (
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TYPE_CHECKING,
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Any,
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Dict,
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Iterable,
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List,
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Mapping,
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Optional,
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Tuple,
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Union,
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)
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from langchain.docstore.document import Document
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from langchain.embeddings.base import Embeddings
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from langchain.utils import get_from_env
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from langchain.vectorstores.base import VectorStore
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if TYPE_CHECKING:
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from elasticsearch import Elasticsearch
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def _default_text_mapping(dim: int) -> Dict:
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return {
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"properties": {
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"text": {"type": "text"},
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"vector": {"type": "dense_vector", "dims": dim},
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}
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}
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def _default_script_query(query_vector: List[float], filter: Optional[dict]) -> Dict:
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if filter:
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((key, value),) = filter.items()
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filter = {"match": {f"metadata.{key}.keyword": f"{value}"}}
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else:
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filter = {"match_all": {}}
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return {
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"script_score": {
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"query": filter,
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"script": {
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"source": "cosineSimilarity(params.query_vector, 'vector') + 1.0",
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"params": {"query_vector": query_vector},
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},
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}
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}
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# ElasticVectorSearch is a concrete implementation of the abstract base class
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# VectorStore, which defines a common interface for all vector database
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# implementations. By inheriting from the ABC class, ElasticVectorSearch can be
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# defined as an abstract base class itself, allowing the creation of subclasses with
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# their own specific implementations. If you plan to subclass ElasticVectorSearch,
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# you can inherit from it and define your own implementation of the necessary methods
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# and attributes.
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class ElasticVectorSearch(VectorStore, ABC):
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"""Wrapper around Elasticsearch as a vector database.
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To connect to an Elasticsearch instance that does not require
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login credentials, pass the Elasticsearch URL and index name along with the
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embedding object to the constructor.
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Example:
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.. code-block:: python
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from langchain import ElasticVectorSearch
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from langchain.embeddings import OpenAIEmbeddings
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embedding = OpenAIEmbeddings()
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elastic_vector_search = ElasticVectorSearch(
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elasticsearch_url="http://localhost:9200",
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index_name="test_index",
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embedding=embedding
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)
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To connect to an Elasticsearch instance that requires login credentials,
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including Elastic Cloud, use the Elasticsearch URL format
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https://username:password@es_host:9243. For example, to connect to Elastic
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Cloud, create the Elasticsearch URL with the required authentication details and
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pass it to the ElasticVectorSearch constructor as the named parameter
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elasticsearch_url.
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You can obtain your Elastic Cloud URL and login credentials by logging in to the
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Elastic Cloud console at https://cloud.elastic.co, selecting your deployment, and
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navigating to the "Deployments" page.
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To obtain your Elastic Cloud password for the default "elastic" user:
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1. Log in to the Elastic Cloud console at https://cloud.elastic.co
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2. Go to "Security" > "Users"
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3. Locate the "elastic" user and click "Edit"
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4. Click "Reset password"
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5. Follow the prompts to reset the password
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The format for Elastic Cloud URLs is
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https://username:password@cluster_id.region_id.gcp.cloud.es.io:9243.
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Example:
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.. code-block:: python
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from langchain import ElasticVectorSearch
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from langchain.embeddings import OpenAIEmbeddings
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embedding = OpenAIEmbeddings()
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elastic_host = "cluster_id.region_id.gcp.cloud.es.io"
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elasticsearch_url = f"https://username:password@{elastic_host}:9243"
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elastic_vector_search = ElasticVectorSearch(
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elasticsearch_url=elasticsearch_url,
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index_name="test_index",
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embedding=embedding
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)
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Args:
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elasticsearch_url (str): The URL for the Elasticsearch instance.
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index_name (str): The name of the Elasticsearch index for the embeddings.
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embedding (Embeddings): An object that provides the ability to embed text.
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It should be an instance of a class that subclasses the Embeddings
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abstract base class, such as OpenAIEmbeddings()
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Raises:
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ValueError: If the elasticsearch python package is not installed.
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"""
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def __init__(
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self,
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elasticsearch_url: str,
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index_name: str,
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embedding: Embeddings,
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*,
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ssl_verify: Optional[Dict[str, Any]] = None,
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):
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"""Initialize with necessary components."""
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try:
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import elasticsearch
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except ImportError:
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raise ImportError(
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"Could not import elasticsearch python package. "
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"Please install it with `pip install elasticsearch`."
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)
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self.embedding = embedding
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self.index_name = index_name
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_ssl_verify = ssl_verify or {}
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try:
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self.client = elasticsearch.Elasticsearch(elasticsearch_url, **_ssl_verify)
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except ValueError as e:
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raise ValueError(
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f"Your elasticsearch client string is mis-formatted. Got error: {e} "
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)
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def add_texts(
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self,
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texts: Iterable[str],
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metadatas: Optional[List[dict]] = None,
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refresh_indices: bool = True,
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**kwargs: Any,
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) -> List[str]:
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"""Run more texts through the embeddings and add to the vectorstore.
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Args:
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texts: Iterable of strings to add to the vectorstore.
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metadatas: Optional list of metadatas associated with the texts.
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refresh_indices: bool to refresh ElasticSearch indices
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Returns:
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List of ids from adding the texts into the vectorstore.
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"""
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try:
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from elasticsearch.exceptions import NotFoundError
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from elasticsearch.helpers import bulk
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except ImportError:
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raise ImportError(
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"Could not import elasticsearch python package. "
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"Please install it with `pip install elasticsearch`."
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)
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requests = []
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ids = []
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embeddings = self.embedding.embed_documents(list(texts))
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dim = len(embeddings[0])
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mapping = _default_text_mapping(dim)
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# check to see if the index already exists
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try:
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self.client.indices.get(index=self.index_name)
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except NotFoundError:
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# TODO would be nice to create index before embedding,
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# just to save expensive steps for last
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self.create_index(self.client, self.index_name, mapping)
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for i, text in enumerate(texts):
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metadata = metadatas[i] if metadatas else {}
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_id = str(uuid.uuid4())
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request = {
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"_op_type": "index",
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"_index": self.index_name,
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"vector": embeddings[i],
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"text": text,
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"metadata": metadata,
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"_id": _id,
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}
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ids.append(_id)
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requests.append(request)
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bulk(self.client, requests)
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if refresh_indices:
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self.client.indices.refresh(index=self.index_name)
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return ids
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def similarity_search(
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self, query: str, k: int = 4, filter: Optional[dict] = None, **kwargs: Any
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) -> List[Document]:
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"""Return docs most similar to query.
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Args:
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query: Text to look up documents similar to.
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k: Number of Documents to return. Defaults to 4.
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Returns:
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List of Documents most similar to the query.
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"""
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docs_and_scores = self.similarity_search_with_score(query, k, filter=filter)
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documents = [d[0] for d in docs_and_scores]
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return documents
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def similarity_search_with_score(
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self, query: str, k: int = 4, filter: Optional[dict] = None, **kwargs: Any
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) -> List[Tuple[Document, float]]:
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"""Return docs most similar to query.
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Args:
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query: Text to look up documents similar to.
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k: Number of Documents to return. Defaults to 4.
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Returns:
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List of Documents most similar to the query.
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"""
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embedding = self.embedding.embed_query(query)
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script_query = _default_script_query(embedding, filter)
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response = self.client_search(
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self.client, self.index_name, script_query, size=k
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)
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hits = [hit for hit in response["hits"]["hits"]]
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docs_and_scores = [
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(
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Document(
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page_content=hit["_source"]["text"],
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metadata=hit["_source"]["metadata"],
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),
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hit["_score"],
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)
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for hit in hits
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]
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return docs_and_scores
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@classmethod
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def from_texts(
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cls,
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texts: List[str],
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embedding: Embeddings,
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metadatas: Optional[List[dict]] = None,
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elasticsearch_url: Optional[str] = None,
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index_name: Optional[str] = None,
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refresh_indices: bool = True,
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**kwargs: Any,
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) -> ElasticVectorSearch:
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"""Construct ElasticVectorSearch wrapper from raw documents.
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This is a user-friendly interface that:
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1. Embeds documents.
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2. Creates a new index for the embeddings in the Elasticsearch instance.
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3. Adds the documents to the newly created Elasticsearch index.
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This is intended to be a quick way to get started.
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Example:
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.. code-block:: python
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from langchain import ElasticVectorSearch
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from langchain.embeddings import OpenAIEmbeddings
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embeddings = OpenAIEmbeddings()
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elastic_vector_search = ElasticVectorSearch.from_texts(
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texts,
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embeddings,
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elasticsearch_url="http://localhost:9200"
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)
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"""
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elasticsearch_url = elasticsearch_url or get_from_env(
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"elasticsearch_url", "ELASTICSEARCH_URL"
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)
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index_name = index_name or uuid.uuid4().hex
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vectorsearch = cls(elasticsearch_url, index_name, embedding, **kwargs)
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vectorsearch.add_texts(
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texts, metadatas=metadatas, refresh_indices=refresh_indices
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)
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return vectorsearch
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def create_index(self, client: Any, index_name: str, mapping: Dict) -> None:
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version_num = client.info()["version"]["number"][0]
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version_num = int(version_num)
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if version_num >= 8:
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client.indices.create(index=index_name, mappings=mapping)
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else:
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client.indices.create(index=index_name, body={"mappings": mapping})
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def client_search(
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self, client: Any, index_name: str, script_query: Dict, size: int
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) -> Any:
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version_num = client.info()["version"]["number"][0]
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version_num = int(version_num)
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if version_num >= 8:
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response = client.search(index=index_name, query=script_query, size=size)
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else:
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response = client.search(
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index=index_name, body={"query": script_query, "size": size}
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)
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return response
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class ElasticKnnSearch(ElasticVectorSearch):
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"""
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A class for performing k-Nearest Neighbors (k-NN) search on an Elasticsearch index.
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The class is designed for a text search scenario where documents are text strings
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and their embeddings are vector representations of those strings.
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"""
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def __init__(
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self,
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index_name: str,
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embedding: Embeddings,
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es_connection: Optional["Elasticsearch"] = None,
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es_cloud_id: Optional[str] = None,
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es_user: Optional[str] = None,
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es_password: Optional[str] = None,
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):
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"""
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Initializes an instance of the ElasticKnnSearch class and sets up the
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Elasticsearch client.
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Args:
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index_name: The name of the Elasticsearch index.
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embedding: An instance of the Embeddings class, used to generate vector
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representations of text strings.
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es_connection: An existing Elasticsearch connection.
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es_cloud_id: The Cloud ID of the Elasticsearch instance. Required if
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creating a new connection.
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es_user: The username for the Elasticsearch instance. Required if
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creating a new connection.
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es_password: The password for the Elasticsearch instance. Required if
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creating a new connection.
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"""
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try:
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import elasticsearch
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except ImportError:
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raise ImportError(
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"Could not import elasticsearch python package. "
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"Please install it with `pip install elasticsearch`."
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)
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self.embedding = embedding
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self.index_name = index_name
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# If a pre-existing Elasticsearch connection is provided, use it.
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if es_connection is not None:
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self.client = es_connection
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else:
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# If credentials for a new Elasticsearch connection are provided,
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# create a new connection.
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if es_cloud_id and es_user and es_password:
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self.client = elasticsearch.Elasticsearch(
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cloud_id=es_cloud_id, basic_auth=(es_user, es_password)
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)
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else:
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raise ValueError(
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"""Either provide a pre-existing Elasticsearch connection, \
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or valid credentials for creating a new connection."""
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)
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@staticmethod
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def _default_knn_mapping(dims: int) -> Dict:
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"""Generates a default index mapping for kNN search."""
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return {
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"properties": {
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"text": {"type": "text"},
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"vector": {
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"type": "dense_vector",
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"dims": dims,
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"index": True,
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"similarity": "dot_product",
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},
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}
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}
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@staticmethod
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def _default_knn_query(
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query_vector: Optional[List[float]] = None,
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query: Optional[str] = None,
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model_id: Optional[str] = None,
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field: Optional[str] = "vector",
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k: Optional[int] = 10,
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num_candidates: Optional[int] = 10,
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) -> Dict:
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knn: Dict = {
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"field": field,
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"k": k,
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"num_candidates": num_candidates,
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}
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# Case 1: `query_vector` is provided, but not `model_id` -> use query_vector
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if query_vector and not model_id:
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knn["query_vector"] = query_vector
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# Case 2: `query` and `model_id` are provided, -> use query_vector_builder
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elif query and model_id:
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knn["query_vector_builder"] = {
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"text_embedding": {
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"model_id": model_id, # use 'model_id' argument
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"model_text": query, # use 'query' argument
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}
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}
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else:
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raise ValueError(
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"Either `query_vector` or `model_id` must be provided, but not both."
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)
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return knn
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def knn_search(
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self,
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query: Optional[str] = None,
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k: Optional[int] = 10,
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query_vector: Optional[List[float]] = None,
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model_id: Optional[str] = None,
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size: Optional[int] = 10,
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source: Optional[bool] = True,
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fields: Optional[
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Union[List[Mapping[str, Any]], Tuple[Mapping[str, Any], ...], None]
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] = None,
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) -> Dict:
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"""
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Performs a k-nearest neighbor (k-NN) search on the Elasticsearch index.
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The search can be conducted using either a raw query vector or a model ID.
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The method first generates
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the body of the search query, which can be interpreted by Elasticsearch.
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It then performs the k-NN
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search on the Elasticsearch index and returns the results.
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Args:
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query: The query or queries to be used for the search. Required if
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`query_vector` is not provided.
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k: The number of nearest neighbors to return. Defaults to 10.
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query_vector: The query vector to be used for the search. Required if
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`query` is not provided.
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model_id: The ID of the model to use for generating the query vector, if
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`query` is provided.
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size: The number of search hits to return. Defaults to 10.
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source: Whether to include the source of each hit in the results.
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fields: The fields to include in the source of each hit. If None, all
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fields are included.
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Returns:
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The search results.
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Raises:
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ValueError: If neither `query_vector` nor `model_id` is provided, or if
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both are provided.
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"""
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knn_query_body = self._default_knn_query(
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query_vector=query_vector, query=query, model_id=model_id, k=k
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)
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# Perform the kNN search on the Elasticsearch index and return the results.
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res = self.client.search(
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index=self.index_name,
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knn=knn_query_body,
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size=size,
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source=source,
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fields=fields,
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)
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return dict(res)
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def knn_hybrid_search(
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self,
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query: Optional[str] = None,
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k: Optional[int] = 10,
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query_vector: Optional[List[float]] = None,
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model_id: Optional[str] = None,
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size: Optional[int] = 10,
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source: Optional[bool] = True,
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knn_boost: Optional[float] = 0.9,
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query_boost: Optional[float] = 0.1,
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fields: Optional[
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Union[List[Mapping[str, Any]], Tuple[Mapping[str, Any], ...], None]
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] = None,
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) -> Dict[Any, Any]:
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"""Performs a hybrid k-nearest neighbor (k-NN) and text-based search on the
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Elasticsearch index.
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The search can be conducted using either a raw query vector or a model ID.
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The method first generates
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the body of the k-NN search query and the text-based query, which can be
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interpreted by Elasticsearch.
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It then performs the hybrid search on the Elasticsearch index and returns the
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results.
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Args:
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query: The query or queries to be used for the search. Required if
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`query_vector` is not provided.
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k: The number of nearest neighbors to return. Defaults to 10.
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query_vector: The query vector to be used for the search. Required if
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`query` is not provided.
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model_id: The ID of the model to use for generating the query vector, if
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`query` is provided.
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size: The number of search hits to return. Defaults to 10.
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source: Whether to include the source of each hit in the results.
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knn_boost: The boost factor for the k-NN part of the search.
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query_boost: The boost factor for the text-based part of the search.
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fields
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|
The fields to include in the source of each hit. If None, all fields are
|
|
included. Defaults to None.
|
|
|
|
Returns:
|
|
The search results.
|
|
|
|
Raises:
|
|
ValueError: If neither `query_vector` nor `model_id` is provided, or if
|
|
both are provided.
|
|
"""
|
|
|
|
knn_query_body = self._default_knn_query(
|
|
query_vector=query_vector, query=query, model_id=model_id, k=k
|
|
)
|
|
|
|
# Modify the knn_query_body to add a "boost" parameter
|
|
knn_query_body["boost"] = knn_boost
|
|
|
|
# Generate the body of the standard Elasticsearch query
|
|
match_query_body = {"match": {"text": {"query": query, "boost": query_boost}}}
|
|
|
|
# Perform the hybrid search on the Elasticsearch index and return the results.
|
|
res = self.client.search(
|
|
index=self.index_name,
|
|
query=match_query_body,
|
|
knn=knn_query_body,
|
|
fields=fields,
|
|
size=size,
|
|
source=source,
|
|
)
|
|
return dict(res)
|