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Cover image for Chat With Your PDFs PART 1: An End-to-End LangChain Tutorial
Austin Vance for Focused

Posted on • Originally published at focused.io

Chat With Your PDFs PART 1: An End-to-End LangChain Tutorial

A common use case for developing AI chat bots is ingesting PDF documents and allowing users to ask questions, inspect the documents, and learn from them. In this tutorial we will start with a 100% blank project and build an end-to-end chat application that allows users to chat about the Epic Games vs Apple Lawsuit. There's a lot of content packed into this one video so please ask questions in the comments and I will do my best to help you get past any hurdles.

In Part 1 You will Learn:

  • Create a new app using ‪@LangChain‬ 's LangServe
  • ingestion of PDFs using ‪@unstructuredio‬
  • Chunking of documents via ‪@LangChain‬'s SemanticChunker
  • Embedding chunks using ‪@OpenAI‬'s embeddings API
  • Storing embedded chunks into a PGVector a vector database
  • Build a LCEL Chain for LangServe that uses PGVector as a retriever
  • Use the LangServe playground as a way to test our RAG
  • Stream output including document sources to a future front end.

In Part 2 we will focus on:

  • Creating a front end with Typescript, React, and Tailwind
  • Display sources of information along with the LLM output
  • Stream to the frontend with Server Sent Events

In Part 3 we will focus:

In Part 4 we will focus on:

  • Adding Memory to the ‪@LangChain‬ Chain with PostgreSQL
  • Add Multiquery to the chain for better breadth of search
  • Add sessions to the Chat History

Github repo

https://github.com/focused-labs/pdf_rag

Chapters

0:00 - Intro

0:49 - Start a New LangServe Project

2:22 - Start Building the Document Importer

11:40 - Use the Semantic Chunker

17:05 - Install & Use PGVector

26:45 - Build the LLM Chain with LCEL

32:00 - Retrieve Documents from PGVector

36:10 - Complete the Chain

39:35 - Inspect Documents coming back from Retriever

40:40 - Use the Chain in LangServe

42:00 - Add Types to your Chain

43:50 - Use the LangServe Playground

45:00 - Recap

46:40 - Next time we will...

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