Milvus Document Store for Haystack

Installation

pip install --upgrade pymilvus milvus-haystack

Usage

Use the MilvusDocumentStore in a Haystack pipeline as a quick start.

from haystack import Document
from milvus_haystack import MilvusDocumentStore

document_store = MilvusDocumentStore(
    connection_args={"uri": "./milvus.db"},
    drop_old=True,
)
documents = [Document(
    content="A Foo Document",
    meta={"page": "100", "chapter": "intro"},
    embedding=[-10.0] * 128,
)]
document_store.write_documents(documents)
print(document_store.count_documents())  # 1

Different ways to connect to Milvus

• For the case of Milvus Lite, the most convenient method, just set the uri as a local file.

document_store = MilvusDocumentStore(
    connection_args={"uri": "./milvus.db"},
    drop_old=True,
)

• For the case of Milvus server on docker or kubernetes, it is recommended to use when you are dealing with large scale of data. After starting the Milvus service, you can use the specified uri to connect to the service.

document_store = MilvusDocumentStore(
    connection_args={"uri": "http://localhost:19530"},
    drop_old=True,
)

• For the case of Zilliz Cloud, the fully managed cloud service for Milvus, adjust the uri and token, which correspond to the Public Endpoint and Api key in Zilliz Cloud.

from haystack.utils import Secret
document_store = MilvusDocumentStore(
    connection_args={
        "uri": "https://in03-ba4234asae.api.gcp-us-west1.zillizcloud.com",  # Your Public Endpoint
        "token": Secret.from_env_var("ZILLIZ_CLOUD_API_KEY"),  # API key, we recommend using the Secret class to load the token from env variable for security.
        "secure": True
    },
    drop_old=True,
)

Dive deep usage

Prepare an OpenAI API key and set it as an environment variable:

export OPENAI_API_KEY=<your_api_key>

Create the indexing Pipeline and index some documents

import glob
import os

from haystack import Pipeline
from haystack.components.converters import MarkdownToDocument
from haystack.components.embedders import OpenAIDocumentEmbedder, OpenAITextEmbedder
from haystack.components.preprocessors import DocumentSplitter
from haystack.components.writers import DocumentWriter

from milvus_haystack import MilvusDocumentStore
from milvus_haystack.milvus_embedding_retriever import MilvusEmbeddingRetriever

current_file_path = os.path.abspath(__file__)
file_paths = [current_file_path]  # You can replace it with your own file paths.

document_store = MilvusDocumentStore(
    connection_args={"uri": "./milvus.db"},
    drop_old=True,
)
indexing_pipeline = Pipeline()
indexing_pipeline.add_component("converter", MarkdownToDocument())
indexing_pipeline.add_component("splitter", DocumentSplitter(split_by="sentence", split_length=2))
indexing_pipeline.add_component("embedder", OpenAIDocumentEmbedder())
indexing_pipeline.add_component("writer", DocumentWriter(document_store))
indexing_pipeline.connect("converter", "splitter")
indexing_pipeline.connect("splitter", "embedder")
indexing_pipeline.connect("embedder", "writer")
indexing_pipeline.run({"converter": {"sources": file_paths}})

print("Number of documents:", document_store.count_documents())

Create the retrieval pipeline and try a query

question = "How to set the service uri with milvus lite?"  # You can replace it with your own question. 

retrieval_pipeline = Pipeline()
retrieval_pipeline.add_component("embedder", OpenAITextEmbedder())
retrieval_pipeline.add_component("retriever", MilvusEmbeddingRetriever(document_store=document_store, top_k=3))
retrieval_pipeline.connect("embedder", "retriever")

retrieval_results = retrieval_pipeline.run({"embedder": {"text": question}})

for doc in retrieval_results["retriever"]["documents"]:
    print(doc.content)
    print("-" * 10)

Create the RAG pipeline and try a query

from haystack.utils import Secret
from haystack.components.builders import PromptBuilder
from haystack.components.generators import OpenAIGenerator

prompt_template = """Answer the following query based on the provided context. If the context does
                     not include an answer, reply with 'I don't know'.\n
                     Query: {{query}}
                     Documents:
                     {% for doc in documents %}
                        {{ doc.content }}
                     {% endfor %}
                     Answer: 
                  """

rag_pipeline = Pipeline()
rag_pipeline.add_component("text_embedder", OpenAITextEmbedder())
rag_pipeline.add_component("retriever", MilvusEmbeddingRetriever(document_store=document_store, top_k=3))
rag_pipeline.add_component("prompt_builder", PromptBuilder(template=prompt_template))
rag_pipeline.add_component("generator", OpenAIGenerator(api_key=Secret.from_token(os.getenv("OPENAI_API_KEY")),
                                                        generation_kwargs={"temperature": 0}))
rag_pipeline.connect("text_embedder.embedding", "retriever.query_embedding")
rag_pipeline.connect("retriever.documents", "prompt_builder.documents")
rag_pipeline.connect("prompt_builder", "generator")

results = rag_pipeline.run(
    {
        "text_embedder": {"text": question},
        "prompt_builder": {"query": question},
    }
)
print('RAG answer:', results["generator"]["replies"][0])

Sparse Retrieval

from haystack import Document, Pipeline
from haystack.components.writers import DocumentWriter
from haystack.document_stores.types import DuplicatePolicy
from haystack_integrations.components.embedders.fastembed import (
    FastembedSparseDocumentEmbedder,
    FastembedSparseTextEmbedder,
)

from milvus_haystack import MilvusDocumentStore, MilvusSparseEmbeddingRetriever

document_store = MilvusDocumentStore(
    connection_args={"uri": "./milvus.db"},
    sparse_vector_field="sparse_vector",  # Specify a name of the sparse vector field to enable sparse retrieval.
    drop_old=True,
)

documents = [
    Document(content="My name is Wolfgang and I live in Berlin"),
    Document(content="I saw a black horse running"),
    Document(content="Germany has many big cities"),
    Document(content="fastembed is supported by and maintained by Milvus."),
]

sparse_document_embedder = FastembedSparseDocumentEmbedder()
writer = DocumentWriter(document_store=document_store, policy=DuplicatePolicy.OVERWRITE)

indexing_pipeline = Pipeline()
indexing_pipeline.add_component("sparse_document_embedder", sparse_document_embedder)
indexing_pipeline.add_component("writer", writer)
indexing_pipeline.connect("sparse_document_embedder", "writer")

indexing_pipeline.run({"sparse_document_embedder": {"documents": documents}})

query_pipeline = Pipeline()
query_pipeline.add_component("sparse_text_embedder", FastembedSparseTextEmbedder())
query_pipeline.add_component("sparse_retriever", MilvusSparseEmbeddingRetriever(document_store=document_store))
query_pipeline.connect("sparse_text_embedder.sparse_embedding", "sparse_retriever.query_sparse_embedding")

query = "Who supports fastembed?"

result = query_pipeline.run({"sparse_text_embedder": {"text": query}})

print(result["sparse_retriever"]["documents"][0])

# Document(id=..., content: 'fastembed is supported by and maintained by Milvus.', sparse_embedding: vector with 48 non-zero elements)

Hybrid Retrieval

from haystack import Document, Pipeline
from haystack.components.embedders import OpenAIDocumentEmbedder, OpenAITextEmbedder
from haystack.components.writers import DocumentWriter
from haystack.document_stores.types import DuplicatePolicy
from haystack_integrations.components.embedders.fastembed import (
    FastembedSparseDocumentEmbedder,
    FastembedSparseTextEmbedder,
)

from milvus_haystack import MilvusDocumentStore, MilvusHybridRetriever

document_store = MilvusDocumentStore(
    connection_args={"uri": "./milvus.db"},
    drop_old=True,
    sparse_vector_field="sparse_vector",  # Specify a name of the sparse vector field to enable hybrid retrieval.
)

documents = [
    Document(content="My name is Wolfgang and I live in Berlin"),
    Document(content="I saw a black horse running"),
    Document(content="Germany has many big cities"),
    Document(content="fastembed is supported by and maintained by Milvus."),
]

writer = DocumentWriter(document_store=document_store, policy=DuplicatePolicy.OVERWRITE)

indexing_pipeline = Pipeline()
indexing_pipeline.add_component("sparse_doc_embedder", FastembedSparseDocumentEmbedder())
indexing_pipeline.add_component("dense_doc_embedder", OpenAIDocumentEmbedder())
indexing_pipeline.add_component("writer", writer)
indexing_pipeline.connect("sparse_doc_embedder", "dense_doc_embedder")
indexing_pipeline.connect("dense_doc_embedder", "writer")

indexing_pipeline.run({"sparse_doc_embedder": {"documents": documents}})

querying_pipeline = Pipeline()
querying_pipeline.add_component("sparse_text_embedder",
                                FastembedSparseTextEmbedder(model="prithvida/Splade_PP_en_v1"))

querying_pipeline.add_component("dense_text_embedder", OpenAITextEmbedder())
querying_pipeline.add_component(
    "retriever",
    MilvusHybridRetriever(
        document_store=document_store,
        # reranker=WeightedRanker(0.5, 0.5),  # Default is RRFRanker()
    )
)

querying_pipeline.connect("sparse_text_embedder.sparse_embedding", "retriever.query_sparse_embedding")
querying_pipeline.connect("dense_text_embedder.embedding", "retriever.query_embedding")

question = "Who supports fastembed?"

results = querying_pipeline.run(
    {"dense_text_embedder": {"text": question},
     "sparse_text_embedder": {"text": question}}
)

print(results["retriever"]["documents"][0])

# Document(id=..., content: 'fastembed is supported by and maintained by Milvus.', embedding: vector of size 1536, sparse_embedding: vector with 48 non-zero elements)

License

milvus-haystack is distributed under the terms of the Apache-2.0 license.