FlashRank 重排器
FlashRank 是一个超轻量级和超快速的 Python 库，可用于为现有的搜索和检索流程添加重新排名功能。它基于最先进的交叉编码器，对所有模型所有者表示感谢。
这篇笔记展示了如何使用 flashrank 进行文档压缩和检索。
%pip install --upgrade --quiet flashrank
%pip install --upgrade --quiet faiss
# 或者（取决于 Python 版本）
%pip install --upgrade --quiet faiss_cpu
# 用于打印文档的辅助函数
def pretty_print_docs(docs):
print(
f"\n{'-' * 100}\n".join(
[
f"Document {i+1}:\n\n{d.page_content}\nMetadata: {d.metadata}"
for i, d in enumerate(docs)
]
)
)
设置基本向量存储检索器
让我们从初始化一个简单的向量存储检索器开始，并存储 2023 年国情咨文（以块形式）。我们可以设置检索器以检索大量（20 个）文档。
import getpass
import os
os.environ["OPENAI_API_KEY"] = getpass.getpass()
from langchain_community.document_loaders import TextLoader
from langchain_community.vectorstores import FAISS
from langchain_openai import OpenAIEmbeddings
from langchain_text_splitters import RecursiveCharacterTextSplitter
documents = TextLoader(
"../../how_to/state_of_the_union.txt",
).load()
text_splitter = RecursiveCharacterTextSplitter(chunk_size=500, chunk_overlap=100)
texts = text_splitter.split_documents(documents)
for idx, text in enumerate(texts):
text.metadata["id"] = idx
embedding = OpenAIEmbeddings(model="text-embedding-ada-002")
retriever = FAISS.from_documents(texts, embedding).as_retriever(search_kwargs={"k": 20})
query = "What did the president say about Ketanji Brown Jackson"
docs = retriever.invoke(query)
pretty_print_docs(docs)
Document 1:
One of the most serious constitutional responsibilities a President has is nominating someone to serve on the United States Supreme Court.
And I did that 4 days ago, when I nominated Circuit Court of Appeals Judge Ketanji Brown Jackson. One of our nation’s top legal minds, who will continue Justice Breyer’s legacy of excellence.
Metadata: {'id': 0}
----------------------------------------------------------------------------------------------------
Document 2:
As I said last year, especially to our younger transgender Americans, I will always have your back as your President, so you can be yourself and reach your God-given potential.
While it often appears that we never agree, that isn’t true. I signed 80 bipartisan bills into law last year. From preventing government shutdowns to protecting Asian-Americans from still-too-common hate crimes to reforming military justice.
Metadata: {'id': 1}
----------------------------------------------------------------------------------------------------
Document 3:
A former top litigator in private practice. A former federal public defender. And from a family of public school educators and police officers. A consensus builder. Since she’s been nominated, she’s received a broad range of support—from the Fraternal Order of Police to former judges appointed by Democrats and Republicans.
And if we are to advance liberty and justice, we need to secure the Border and fix the immigration system.
Metadata: {'id': 2}
----------------------------------------------------------------------------------------------------
Document 4:
He met the Ukrainian people.
From President Zelenskyy to every Ukrainian, their fearlessness, their courage, their determination, inspires the world.
Groups of citizens blocking tanks with their bodies. Everyone from students to retirees teachers turned soldiers defending their homeland.
In this struggle as President Zelenskyy said in his speech to the European Parliament “Light will win over darkness.” The Ukrainian Ambassador to the United States is here tonight.
Metadata: {'id': 3}
----------------------------------------------------------------------------------------------------
Document 5:
But that trickle-down theory led to weaker economic growth, lower wages, bigger deficits, and the widest gap between those at the top and everyone else in nearly a century.
Vice President Harris and I ran for office with a new economic vision for America.
Invest in America. Educate Americans. Grow the workforce. Build the economy from the bottom up and the middle out, not from the top down.
Metadata: {'id': 4}
----------------------------------------------------------------------------------------------------
Document 6:
And tonight, I’m announcing that the Justice Department will name a chief prosecutor for pandemic fraud.
By the end of this year, the deficit will be down to less than half what it was before I took office.
The only president ever to cut the deficit by more than one trillion dollars in a single year.
Lowering your costs also means demanding more competition.
I’m a capitalist, but capitalism without competition isn’t capitalism.
It’s exploitation—and it drives up prices.
Metadata: {'id': 5}
----------------------------------------------------------------------------------------------------
Document 7:
I spoke with their families and told them that we are forever in debt for their sacrifice, and we will carry on their mission to restore the trust and safety every community deserves.
I’ve worked on these issues a long time.
I know what works: Investing in crime prevention and community police officers who’ll walk the beat, who’ll know the neighborhood, and who can restore trust and safety.
So let’s not abandon our streets. Or choose between safety and equal justice.
Metadata: {'id': 6}
----------------------------------------------------------------------------------------------------
Document 8:
As I’ve told Xi Jinping, it is never a good bet to bet against the American people.
We’ll create good jobs for millions of Americans, modernizing roads, airports, ports, and waterways all across America.
And we’ll do it all to withstand the devastating effects of the climate crisis and promote environmental justice.
Metadata: {'id': 7}
----------------------------------------------------------------------------------------------------
Document 9:
Madam Speaker, Madam Vice President, our First Lady and Second Gentleman. Members of Congress and the Cabinet. Justices of the Supreme Court. My fellow Americans.
Last year COVID-19 kept us apart. This year we are finally together again.
Tonight, we meet as Democrats Republicans and Independents. But most importantly as Americans.
With a duty to one another to the American people to the Constitution.
And with an unwavering resolve that freedom will always triumph over tyranny.
Metadata: {'id': 8}
----------------------------------------------------------------------------------------------------
Document 10:
As Ohio Senator Sherrod Brown says, “It’s time to bury the label “Rust Belt.”
It’s time.
But with all the bright spots in our economy, record job growth and higher wages, too many families are struggling to keep up with the bills.
Inflation is robbing them of the gains they might otherwise feel.
I get it. That’s why my top priority is getting prices under control.
Metadata: {'id': 9}
----------------------------------------------------------------------------------------------------
Document 11:
I’m also calling on Congress: pass a law to make sure veterans devastated by toxic exposures in Iraq and Afghanistan finally get the benefits and comprehensive health care they deserve.
And fourth, let’s end cancer as we know it.
This is personal to me and Jill, to Kamala, and to so many of you.
Cancer is the #2 cause of death in America–second only to heart disease.
Metadata: {'id': 10}
----------------------------------------------------------------------------------------------------
Document 12:
Headaches. Numbness. Dizziness.
A cancer that would put them in a flag-draped coffin.
I know.
One of those soldiers was my son Major Beau Biden.
We don’t know for sure if a burn pit was the cause of his brain cancer, or the diseases of so many of our troops.
But I’m committed to finding out everything we can.
Committed to military families like Danielle Robinson from Ohio.
The widow of Sergeant First Class Heath Robinson.
Metadata: {'id': 11}
----------------------------------------------------------------------------------------------------
Document 13:
He will never extinguish their love of freedom. He will never weaken the resolve of the free world.
We meet tonight in an America that has lived through two of the hardest years this nation has ever faced.
The pandemic has been punishing.
And so many families are living paycheck to paycheck, struggling to keep up with the rising cost of food, gas, housing, and so much more.
I understand.
Metadata: {'id': 12}
----------------------------------------------------------------------------------------------------
Document 14:
When we invest in our workers, when we build the economy from the bottom up and the middle out together, we can do something we haven’t done in a long time: build a better America.
For more than two years, COVID-19 has impacted every decision in our lives and the life of the nation.
And I know you’re tired, frustrated, and exhausted.
But I also know this.
Metadata: {'id': 13}
----------------------------------------------------------------------------------------------------
Document 15:
And soon, we’ll strengthen the Violence Against Women Act that I first wrote three decades ago. It is important for us to show the nation that we can come together and do big things.
So tonight I’m offering a Unity Agenda for the Nation. Four big things we can do together.
First, beat the opioid epidemic.
There is so much we can do. Increase funding for prevention, treatment, harm reduction, and recovery.
Metadata: {'id': 14}
----------------------------------------------------------------------------------------------------
Document 16:
My plan to fight inflation will lower your costs and lower the deficit.
17 Nobel laureates in economics say my plan will ease long-term inflationary pressures. Top business leaders and most Americans support my plan. And here’s the plan:
First – cut the cost of prescription drugs. Just look at insulin. One in ten Americans has diabetes. In Virginia, I met a 13-year-old boy named Joshua Davis.
Metadata: {'id': 15}
----------------------------------------------------------------------------------------------------
Document 17:
My plan will not only lower costs to give families a fair shot, it will lower the deficit.
The previous Administration not only ballooned the deficit with tax cuts for the very wealthy and corporations, it undermined the watchdogs whose job was to keep pandemic relief funds from being wasted.
But in my administration, the watchdogs have been welcomed back.
We’re going after the criminals who stole billions in relief money meant for small businesses and millions of Americans.
Metadata: {'id': 16}
----------------------------------------------------------------------------------------------------
Document 18:
So let’s not abandon our streets. Or choose between safety and equal justice.
Let’s come together to protect our communities, restore trust, and hold law enforcement accountable.
That’s why the Justice Department required body cameras, banned chokeholds, and restricted no-knock warrants for its officers.
Metadata: {'id': 17}
----------------------------------------------------------------------------------------------------
Document 19:
I understand.
I remember when my Dad had to leave our home in Scranton, Pennsylvania to find work. I grew up in a family where if the price of food went up, you felt it.
That’s why one of the first things I did as President was fight to pass the American Rescue Plan.
Because people were hurting. We needed to act, and we did.
Few pieces of legislation have done more in a critical moment in our history to lift us out of crisis.
Metadata: {'id': 18}
----------------------------------------------------------------------------------------------------
Document 20:
And we will, as one people.
One America.
The United States of America.
May God bless you all. May God protect our troops.
Metadata: {'id': 19}
使用 FlashRank 进行重新排名
现在让我们用 ContextualCompressionRetriever 将基础检索器包装起来，使用 FlashrankRerank 作为压缩器。
from langchain.retrievers import ContextualCompressionRetriever
from langchain.retrievers.document_compressors import FlashrankRerank
from langchain_openai import ChatOpenAI
llm = ChatOpenAI(temperature=0)
compressor = FlashrankRerank()
compression_retriever = ContextualCompressionRetriever(
base_compressor=compressor, base_retriever=retriever
)
compressed_docs = compression_retriever.invoke(
"What did the president say about Ketanji Jackson Brown"
)
print([doc.metadata["id"] for doc in compressed_docs])
[0, 5, 3]
重新排名后，前 3 个文档与基础检索器检索到的前 3 个文档不同。
pretty_print_docs(compressed_docs)
文档 1：
总统拥有的最严肃的宪法责任之一是提名某人担任美国最高法院的法官。
4 天前，我提名了巡回上诉法院法官 Ketanji Brown Jackson。她是我们国家顶尖的法律专家之一，将继续布雷尔大法官的卓越传统。
----------------------------------------------------------------------------------------------------
文档 2：
他见到了乌克兰人民。
从泽连斯基总统到每一位乌克兰人，他们的无畏、勇气和决心激励着世界。
公民们用自己的身体挡住坦克。从学生到退休教师，他们变成了捍卫家园的士兵。
正如泽连斯基总统在他向欧洲议会的讲话中所说的那样，“光明将战胜黑暗。”乌克兰驻美国大使今晚在这里。
----------------------------------------------------------------------------------------------------
文档 3：
今晚，我宣布司法部将任命一名大流行欺诈的首席检察官。
到今年年底，赤字将减少到我上任前的不到一半。
我是有史以来唯一一位在一年内削减赤字超过一万亿美元的总统。
降低成本也意味着要求更多的竞争。
我是资本家，但没有竞争的资本主义不是真正的资本主义。
这是剥削，它会推高价格。
使用 FlashRank 进行问答重新排名
from langchain.chains import RetrievalQA
chain = RetrievalQA.from_chain_type(llm=llm, retriever=compression_retriever)
chain.invoke(query)
{'query': 'What did the president say about Ketanji Brown Jackson',
'result': "总统提到 Ketanji Brown Jackson 是国家顶尖的法律专家之一，将继续布雷尔大法官的卓越传统。"}