import asyncio
import logging
from typing import List, Optional, Sequence
from langchain_core.callbacks import (
AsyncCallbackManagerForRetrieverRun,
CallbackManagerForRetrieverRun,
)
from langchain_core.documents import Document
from langchain_core.language_models import BaseLanguageModel
from langchain_core.output_parsers import BaseOutputParser
from langchain_core.prompts.prompt import PromptTemplate
from langchain_core.retrievers import BaseRetriever
from langchain.chains.llm import LLMChain
logger = logging.getLogger(__name__)
[docs]class LineListOutputParser(BaseOutputParser[List[str]]):
"""Output parser for a list of lines."""
[docs] def parse(self, text: str) -> List[str]:
lines = text.strip().split("\n")
return lines
# Default prompt
DEFAULT_QUERY_PROMPT = PromptTemplate(
input_variables=["question"],
template="""You are an AI language model assistant. Your task is
to generate 3 different versions of the given user
question to retrieve relevant documents from a vector database.
By generating multiple perspectives on the user question,
your goal is to help the user overcome some of the limitations
of distance-based similarity search. Provide these alternative
questions separated by newlines. Original question: {question}""",
)
def _unique_documents(documents: Sequence[Document]) -> List[Document]:
return [doc for i, doc in enumerate(documents) if doc not in documents[:i]]
[docs]class MultiQueryRetriever(BaseRetriever):
"""Given a query, use an LLM to write a set of queries.
Retrieve docs for each query. Return the unique union of all retrieved docs.
"""
retriever: BaseRetriever
llm_chain: LLMChain
verbose: bool = True
parser_key: str = "lines"
"""DEPRECATED. parser_key is no longer used and should not be specified."""
include_original: bool = False
"""Whether to include the original query in the list of generated queries."""
[docs] @classmethod
def from_llm(
cls,
retriever: BaseRetriever,
llm: BaseLanguageModel,
prompt: PromptTemplate = DEFAULT_QUERY_PROMPT,
parser_key: Optional[str] = None,
include_original: bool = False,
) -> "MultiQueryRetriever":
"""Initialize from llm using default template.
Args:
retriever: retriever to query documents from
llm: llm for query generation using DEFAULT_QUERY_PROMPT
include_original: Whether to include the original query in the list of
generated queries.
Returns:
MultiQueryRetriever
"""
output_parser = LineListOutputParser()
llm_chain = LLMChain(llm=llm, prompt=prompt, output_parser=output_parser)
return cls(
retriever=retriever,
llm_chain=llm_chain,
include_original=include_original,
)
async def _aget_relevant_documents(
self,
query: str,
*,
run_manager: AsyncCallbackManagerForRetrieverRun,
) -> List[Document]:
"""Get relevant documents given a user query.
Args:
question: user query
Returns:
Unique union of relevant documents from all generated queries
"""
queries = await self.agenerate_queries(query, run_manager)
if self.include_original:
queries.append(query)
documents = await self.aretrieve_documents(queries, run_manager)
return self.unique_union(documents)
[docs] async def agenerate_queries(
self, question: str, run_manager: AsyncCallbackManagerForRetrieverRun
) -> List[str]:
"""Generate queries based upon user input.
Args:
question: user query
Returns:
List of LLM generated queries that are similar to the user input
"""
response = await self.llm_chain.acall(
inputs={"question": question}, callbacks=run_manager.get_child()
)
lines = response["text"]
if self.verbose:
logger.info(f"Generated queries: {lines}")
return lines
[docs] async def aretrieve_documents(
self, queries: List[str], run_manager: AsyncCallbackManagerForRetrieverRun
) -> List[Document]:
"""Run all LLM generated queries.
Args:
queries: query list
Returns:
List of retrieved Documents
"""
document_lists = await asyncio.gather(
*(
self.retriever.ainvoke(
query, config={"callbacks": run_manager.get_child()}
)
for query in queries
)
)
return [doc for docs in document_lists for doc in docs]
def _get_relevant_documents(
self,
query: str,
*,
run_manager: CallbackManagerForRetrieverRun,
) -> List[Document]:
"""Get relevant documents given a user query.
Args:
question: user query
Returns:
Unique union of relevant documents from all generated queries
"""
queries = self.generate_queries(query, run_manager)
if self.include_original:
queries.append(query)
documents = self.retrieve_documents(queries, run_manager)
return self.unique_union(documents)
[docs] def generate_queries(
self, question: str, run_manager: CallbackManagerForRetrieverRun
) -> List[str]:
"""Generate queries based upon user input.
Args:
question: user query
Returns:
List of LLM generated queries that are similar to the user input
"""
response = self.llm_chain(
{"question": question}, callbacks=run_manager.get_child()
)
lines = response["text"]
if self.verbose:
logger.info(f"Generated queries: {lines}")
return lines
[docs] def retrieve_documents(
self, queries: List[str], run_manager: CallbackManagerForRetrieverRun
) -> List[Document]:
"""Run all LLM generated queries.
Args:
queries: query list
Returns:
List of retrieved Documents
"""
documents = []
for query in queries:
docs = self.retriever.invoke(
query, config={"callbacks": run_manager.get_child()}
)
documents.extend(docs)
return documents
[docs] def unique_union(self, documents: List[Document]) -> List[Document]:
"""Get unique Documents.
Args:
documents: List of retrieved Documents
Returns:
List of unique retrieved Documents
"""
return _unique_documents(documents)