使用 Milvus 和 Haystack 的检索增强生成（RAG）

本指南演示了如何使用 Haystack 和 Milvus 构建检索-增强生成（RAG）系统。

RAG 系统结合了检索系统和生成模型，可根据给定提示生成新文本。该系统首先使用 Milvus 从语料库中检索相关文档，然后使用生成模型根据检索到的文档生成新文本。

Haystack是 deepset 开发的开源 Python 框架，用于使用大型语言模型（LLM）构建自定义应用程序。Milvus是世界上最先进的开源向量数据库，用于支持嵌入式相似性搜索和人工智能应用。

前提条件

在运行本笔记本之前，请确保已安装以下依赖项：

! pip install --upgrade --quiet pymilvus milvus-haystack markdown-it-py mdit_plain

我们将使用 OpenAI 的模型。您应将api key OPENAI_API_KEY 作为环境变量。

import os

os.environ["OPENAI_API_KEY"] = "sk-****\*\*\*****"

准备数据

我们使用关于达芬奇的在线内容作为 RAG 管道的私人知识库，这对于简单的 RAG 管道来说是一个很好的数据源。

下载并保存为本地文本文件。

import os
import urllib.request

url = "https://www.gutenberg.org/cache/epub/7785/pg7785.txt"
file_path = "./davinci.txt"

if not os.path.exists(file_path):
urllib.request.urlretrieve(url, file_path)

创建索引管道

创建一个索引管道，将文本转换成文档，分割成句子并嵌入其中。然后将文档写入 Milvus 文档存储区。

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 haystack.utils import Secret

from milvus_haystack import MilvusDocumentStore
from milvus_haystack.milvus_embedding_retriever import MilvusEmbeddingRetriever

document_store = MilvusDocumentStore(
connection_args={"uri": "./milvus.db"},
# connection_args={"uri": "http://localhost:19530"},
# connection_args={"uri": YOUR_ZILLIZ_CLOUD_URI, "token": Secret.from_env_var("ZILLIZ_CLOUD_API_KEY")},
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_path]}})

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

Converting markdown files to Documents: 100%|█| 1/
Calculating embeddings: 100%|█| 9/9 [00:05<00:00, 
E20240516 10:40:32.945937 5309095 milvus_local.cpp:189] [SERVER][GetCollection][] Collecton HaystackCollection not existed
E20240516 10:40:32.946677 5309095 milvus_local.cpp:189] [SERVER][GetCollection][] Collecton HaystackCollection not existed
E20240516 10:40:32.946704 5309095 milvus_local.cpp:189] [SERVER][GetCollection][] Collecton HaystackCollection not existed
E20240516 10:40:32.946725 5309095 milvus_local.cpp:189] [SERVER][GetCollection][] Collecton HaystackCollection not existed


Number of documents: 277

创建检索管道

创建检索管道，使用向量相似性搜索引擎从 Milvus 文档存储中检索文档。

question = 'Where is the painting "Warrior" currently stored?'

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)

). The
composition of this oil-painting seems to have been built up on the
second cartoon, which he had made some eight years earlier, and which
was apparently taken to France in 1516 and ultimately lost.
----------

This "Baptism of Christ," which is now in the Accademia in Florence
and is in a bad state of preservation, appears to have been a
comparatively early work by Verrocchio, and to have been painted
in 1480-1482, when Leonardo would be about thirty years of age.

To about this period belongs the superb drawing of the "Warrior," now
in the Malcolm Collection in the British Museum.
----------
" Although he
completed the cartoon, the only part of the composition which he
eventually executed in colour was an incident in the foreground
which dealt with the "Battle of the Standard." One of the many
supposed copies of a study of this mural painting now hangs on the
south-east staircase in the Victoria and Albert Museum.
----------

创建 RAG 管道

创建 RAG 管道，结合 MilvusEmbeddingRetriever 和 OpenAIGenerator，使用检索到的文档回答问题。

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])

RAG answer: The painting "Warrior" is currently stored in the Malcolm Collection in the British Museum.

有关如何使用 milvus-haystack 的更多信息，请参阅milvus-haystack Readme。