Source code for langchain.chains.router.embedding_router

from __future__ import annotations

from collections.abc import Sequence
from typing import Any, Optional

from langchain_core.callbacks import (
    AsyncCallbackManagerForChainRun,
    CallbackManagerForChainRun,
)
from langchain_core.documents import Document
from langchain_core.embeddings import Embeddings
from langchain_core.vectorstores import VectorStore
from pydantic import ConfigDict

from langchain.chains.router.base import RouterChain



[docs]
class EmbeddingRouterChain(RouterChain):
    """Chain that uses embeddings to route between options."""

    vectorstore: VectorStore
    routing_keys: list[str] = ["query"]

    model_config = ConfigDict(
        arbitrary_types_allowed=True,
        extra="forbid",
    )

    @property
    def input_keys(self) -> list[str]:
        """Will be whatever keys the LLM chain prompt expects.

        :meta private:
        """
        return self.routing_keys

    def _call(
        self,
        inputs: dict[str, Any],
        run_manager: Optional[CallbackManagerForChainRun] = None,
    ) -> dict[str, Any]:
        _input = ", ".join([inputs[k] for k in self.routing_keys])
        results = self.vectorstore.similarity_search(_input, k=1)
        return {"next_inputs": inputs, "destination": results[0].metadata["name"]}

    async def _acall(
        self,
        inputs: dict[str, Any],
        run_manager: Optional[AsyncCallbackManagerForChainRun] = None,
    ) -> dict[str, Any]:
        _input = ", ".join([inputs[k] for k in self.routing_keys])
        results = await self.vectorstore.asimilarity_search(_input, k=1)
        return {"next_inputs": inputs, "destination": results[0].metadata["name"]}


[docs]
    @classmethod
    def from_names_and_descriptions(
        cls,
        names_and_descriptions: Sequence[tuple[str, Sequence[str]]],
        vectorstore_cls: type[VectorStore],
        embeddings: Embeddings,
        **kwargs: Any,
    ) -> EmbeddingRouterChain:
        """Convenience constructor."""
        documents = []
        for name, descriptions in names_and_descriptions:
            for description in descriptions:
                documents.append(
                    Document(page_content=description, metadata={"name": name})
                )
        vectorstore = vectorstore_cls.from_documents(documents, embeddings)
        return cls(vectorstore=vectorstore, **kwargs)



[docs]
    @classmethod
    async def afrom_names_and_descriptions(
        cls,
        names_and_descriptions: Sequence[tuple[str, Sequence[str]]],
        vectorstore_cls: type[VectorStore],
        embeddings: Embeddings,
        **kwargs: Any,
    ) -> EmbeddingRouterChain:
        """Convenience constructor."""
        documents = []
        for name, descriptions in names_and_descriptions:
            for description in descriptions:
                documents.append(
                    Document(page_content=description, metadata={"name": name})
                )
        vectorstore = await vectorstore_cls.afrom_documents(documents, embeddings)
        return cls(vectorstore=vectorstore, **kwargs)