This guide provides more details for using the prepdocs script to index documents for the Chat App.
The scripts/prepdocs.py script is responsible for both uploading and indexing documents. The typical usage is to call it using scripts/prepdocs.sh (Mac/Linux) or scripts/prepdocs.ps1 (Windows), as these scripts will set up a Python virtual environment and pass in the required parameters based on the current azd environment. Whenever azd up or azd provision is run, the script is called automatically.
The script uses the following steps to index documents:
- If it doesn't yet exist, create a new index in Azure AI Search.
- Upload the PDFs to Azure Blob Storage.
- Split the PDFs into chunks of text.
- Upload the chunks to Azure AI Search. If using vectors (the default), also compute the embeddings and upload those alongside the text.
We're often asked why we need to break up the PDFs into chunks when Azure AI Search supports searching large documents.
Chunking allows us to limit the amount of information we send to OpenAI due to token limits. By breaking up the content, it allows us to easily find potential chunks of text that we can inject into OpenAI. The method of chunking we use leverages a sliding window of text such that sentences that end one chunk will start the next. This allows us to reduce the chance of losing the context of the text.
If needed, you can modify the chunking algorithm in scripts/prepdocslib/textsplitter.py.
To upload more PDFs, put them in the data/ folder and run ./scripts/prepdocs.sh or ./scripts/prepdocs.ps1.
A recent change added checks to see what's been uploaded before. The prepdocs script now writes an .md5 file with an MD5 hash of each file that gets uploaded. Whenever the prepdocs script is re-run, that hash is checked against the current hash and the file is skipped if it hasn't changed.
You may want to remove documents from the index. For example, if you're using the sample data, you may want to remove the documents that are already in the index before adding your own.
To remove all documents, use the --removeall flag. Open either scripts/prepdocs.sh or scripts/prepdocs.ps1 and add --removeall to the command at the bottom of the file. Then run the script as usual.
You can also remove individual documents by using the --remove flag. Open either scripts/prepdocs.sh or scripts/prepdocs.ps1, add --remove to the command at the bottom of the file, and replace /data/* with /data/YOUR-DOCUMENT-FILENAME-GOES-HERE.pdf. Then run the script as usual.
Azure AI search recently introduced an integrated vectorization feature in preview mode. This feature is a cloud-based approach to data ingestion, which takes care of document format cracking, data extraction, chunking, vectorization, and indexing, all with Azure technologies.
See this notebook to understand the process of setting up integrated vectorization.
We have integrated that code into our prepdocs script, so you can use it without needing to understand the details.
This feature cannot be used on existing index. You need to create a new index or drop and recreate an existing index. In the newly created index schema, a new field 'parent_id' is added. This is used internally by the indexer to manage life cycle of chunks.
This feature is not supported in the free SKU for Azure AI Search.
To add additional documents to the index, first upload them to your data source (Blob storage, by default). Then navigate to the Azure portal, find the index, and run it. The Azure AI Search indexer will identify the new documents and ingest them into the index.
To remove documents from the index, remove them from your data source (Blob storage, by default). Then navigate to the Azure portal, find the index, and run it. The Azure AI Search indexer will take care of removing those documents from the index.
If you would like the indexer to run automatically, you can set it up to run on a schedule.