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互逆重排融合检索器

在本示例中,我们将演示如何结合来自多个查询和多个索引的检索结果。

检索到的节点将根据这篇论文中演示的Reciprocal Rerank Fusion算法进行重新排序。它提供了一种无需过多计算或依赖外部模型即可对检索结果进行重新排序的高效方法。

完整功劳归于 @Raduaschl 在 GitHub 上的示例实现此处

%pip install llama-index-llms-openai
%pip install llama-index-retrievers-bm25
import os
import openai
os.environ["OPENAI_API_KEY"] = "sk-..."
openai.api_key = os.environ["OPENAI_API_KEY"]

如果您在 Colab 上打开这个笔记本,您可能需要安装 LlamaIndex 🦙。

下载数据

!mkdir -p 'data/paul_graham/'
!wget 'https://raw.githubusercontent.com/run-llama/llama_index/main/docs/examples/data/paul_graham/paul_graham_essay.txt' -O 'data/paul_graham/paul_graham_essay.txt'
--2024-02-12 17:59:58-- https://raw.githubusercontent.com/run-llama/llama_index/main/docs/examples/data/paul_graham/paul_graham_essay.txt
Resolving raw.githubusercontent.com (raw.githubusercontent.com)... 2606:50c0:8003::154, 2606:50c0:8001::154, 2606:50c0:8002::154, ...
Connecting to raw.githubusercontent.com (raw.githubusercontent.com)|2606:50c0:8003::154|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 75042 (73K) [text/plain]
Saving to: ‘data/paul_graham/paul_graham_essay.txt’
data/paul_graham/pa 100%[===================>] 73.28K 327KB/s in 0.2s
2024-02-12 17:59:59 (327 KB/s) - ‘data/paul_graham/paul_graham_essay.txt’ saved [75042/75042]
from llama_index.core import SimpleDirectoryReader
documents = SimpleDirectoryReader("./data/paul_graham/").load_data()

接下来,我们将在文档上设置一个向量索引。

from llama_index.core import VectorStoreIndex
from llama_index.core.node_parser import SentenceSplitter
splitter = SentenceSplitter(chunk_size=256)
index = VectorStoreIndex.from_documents(documents, transformations=[splitter])

在这一步中,我们将索引与基于BM25的检索器进行融合。这将使我们能够捕捉输入查询中的语义关系和关键词。

由于这两个检索器都会计算分数,我们可以使用互惠重排算法来重新排序节点,而无需使用额外模型或过多计算。

此设置还将查询4次,一次使用您的原始查询,并生成另外3个查询。

默认情况下,它使用以下提示生成额外查询:

QUERY_GEN_PROMPT = (
"You are a helpful assistant that generates multiple search queries based on a "
"single input query. Generate {num_queries} search queries, one on each line, "
"related to the following input query:\n"
"Query: {query}\n"
"Queries:\n"
)

首先,我们创建检索器。每个检索器将获取前2个最相似的节点:

from llama_index.retrievers.bm25 import BM25Retriever
vector_retriever = index.as_retriever(similarity_top_k=2)
bm25_retriever = BM25Retriever.from_defaults(
docstore=index.docstore, similarity_top_k=2
)

接下来,我们可以创建我们的融合检索器,它将从检索器返回的4个节点中返回前2个最相似的节点:

from llama_index.core.retrievers import QueryFusionRetriever
retriever = QueryFusionRetriever(
[vector_retriever, bm25_retriever],
similarity_top_k=2,
num_queries=4, # set this to 1 to disable query generation
mode="reciprocal_rerank",
use_async=True,
verbose=True,
# query_gen_prompt="...", # we could override the query generation prompt here
)
# apply nested async to run in a notebook
import nest_asyncio
nest_asyncio.apply()
nodes_with_scores = retriever.retrieve(
"What happened at Interleafe and Viaweb?"
)
Generated queries:
1. What were the major events or milestones in the history of Interleafe and Viaweb?
2. Can you provide a timeline of the key developments and achievements of Interleafe and Viaweb?
3. What were the successes and failures of Interleafe and Viaweb as companies?
for node in nodes_with_scores:
print(f"Score: {node.score:.2f} - {node.text}...\n-----\n")
Score: 0.03 - The UI was horrible, but it proved you could build a whole store through the browser, without any client software or typing anything into the command line on the server.
Now we felt like we were really onto something. I had visions of a whole new generation of software working this way. You wouldn't need versions, or ports, or any of that crap. At Interleaf there had been a whole group called Release Engineering that seemed to be at least as big as the group that actually wrote the software. Now you could just update the software right on the server.
We started a new company we called Viaweb, after the fact that our software worked via the web, and we got $10,000 in seed funding from Idelle's husband Julian. In return for that and doing the initial legal work and giving us business advice, we gave him 10% of the company. Ten years later this deal became the model for Y Combinator's. We knew founders needed something like this, because we'd needed it ourselves....
-----
Score: 0.03 - Now we felt like we were really onto something. I had visions of a whole new generation of software working this way. You wouldn't need versions, or ports, or any of that crap. At Interleaf there had been a whole group called Release Engineering that seemed to be at least as big as the group that actually wrote the software. Now you could just update the software right on the server.
We started a new company we called Viaweb, after the fact that our software worked via the web, and we got $10,000 in seed funding from Idelle's husband Julian. In return for that and doing the initial legal work and giving us business advice, we gave him 10% of the company. Ten years later this deal became the model for Y Combinator's. We knew founders needed something like this, because we'd needed it ourselves.
At this stage I had a negative net worth, because the thousand dollars or so I had in the bank was more than counterbalanced by what I owed the government in taxes. (Had I diligently set aside the proper proportion of the money I'd made consulting for Interleaf?...
-----

我们可以看到,两个返回的节点都正确提到了Viaweb和Interleaf!

现在,我们可以将检索器接入查询引擎,以合成自然语言响应。

from llama_index.core.query_engine import RetrieverQueryEngine
query_engine = RetrieverQueryEngine.from_args(retriever)
response = query_engine.query("What happened at Interleafe and Viaweb?")
Generated queries:
1. What were the major events or milestones in the history of Interleafe and Viaweb?
2. Can you provide a timeline of the key developments and achievements of Interleafe and Viaweb?
3. What were the outcomes or impacts of Interleafe and Viaweb on the respective industries they operated in?
from llama_index.core.response.notebook_utils import display_response
display_response(response)

Final Response: 在Interleaf公司,有一个与软件开发团队规模相当的发布工程团队。这表明该公司对软件版本管理和移植工作投入了大量精力。然而在Viaweb,创始人们意识到可以直接在服务器上更新软件,从而消除了版本管理和移植的需求。他们创立了Viaweb公司,专门开发基于网络的软件。他们获得了1万美元的种子资金,并将公司10%的股份给提供了资金和商业建议的Julian。这笔交易后来成为了Y Combinator的投资范本。