> ## Documentation Index
> Fetch the complete documentation index at: https://docs.pixeltable.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Split documents into chunks for RAG
> Split documents into RAG-ready chunks in Pixeltable using DocumentSplitter with overlap, token limits, and structural heading awareness.
This documentation page is also available as an interactive notebook. You can launch the notebook in
Kaggle or Colab, or download it for use with an IDE or local Jupyter installation, by clicking one of the
above links.
export const quartoRawHtml = [`
| Document |
Size |
Chunks needed |
| annual_report.pdf |
50 pages |
~100 chunks |
| user_manual.pdf |
20 pages |
~40 chunks |
| research_paper.pdf |
10 pages |
~20 chunks |
`, `
| text |
| MARKET DIGEST |
| - 1 - |
| FRIDAY, JUNE 21, 2024 |
| JUNE 20, DJIA: 39,134.76 UP 299.90 |
| Independent Equity Research Since 1934 ARGUS |
`, `
| text |
score |
| MARKET REVIEW: |
0.558 |
| This is the Market Digest for Friday, June 21, 2024, with analysis
of the financial markets and comments on Accenture plc. |
0.489 |
| MARKET DIGEST |
0.479 |
`, `
| Separator |
Description |
sentence |
Split on sentence boundaries |
heading |
Split on document headings |
page |
Split on page breaks |
token_limit |
Split at token count only |
`];
Break PDFs and documents into searchable chunks for retrieval-augmented
generation (RAG) pipelines.
## Problem
You have PDF documents or text files that you want to use for
retrieval-augmented generation (RAG). Before you can search them, you
need to:
1. Split documents into smaller chunks
2. Generate embeddings for each chunk
3. Store everything in a searchable index
## Solution
**What’s in this recipe:**
* Split PDFs into sentences with token limits
* Control chunk size with token limits
* Add embeddings for semantic search
You create a view with a `document_splitter` iterator that automatically
breaks documents into chunks. Then you add an embedding index for
semantic search.
### Setup
```python theme={"theme":{"light":"light-plus","dark":"dark-plus"}}
%pip install -qU pixeltable sentence-transformers spacy tiktoken
!python -m spacy download en_core_web_sm -q
```
### Load documents
```python theme={"theme":{"light":"light-plus","dark":"dark-plus"}}
import pixeltable as pxt
from pixeltable.functions.document import document_splitter
from pixeltable.functions.huggingface import sentence_transformer
# Create a fresh directory
pxt.drop_dir('rag_demo', force=True)
pxt.create_dir('rag_demo')
```
Created directory 'rag\_demo'.
\
```python theme={"theme":{"light":"light-plus","dark":"dark-plus"}}
# Create table for documents
docs = pxt.create_table('rag_demo/documents', {'document': pxt.Document})
```
Created table 'documents'.
```python theme={"theme":{"light":"light-plus","dark":"dark-plus"}}
# Insert a sample PDF
docs.insert(
[
{
'document': 'https://raw.githubusercontent.com/pixeltable/pixeltable/main/docs/resources/rag-demo/Argus-Market-Digest-June-2024.pdf'
}
]
)
```
Inserting rows into \`documents\`: 1 rows \[00:00, 775.86 rows/s]
Inserted 1 row with 0 errors.
1 row inserted, 2 values computed.
### Split into chunks
Create a view that splits each document into sentences with a token
limit:
```python theme={"theme":{"light":"light-plus","dark":"dark-plus"}}
# Create a view that splits documents into chunks
chunks = pxt.create_view(
'rag_demo/chunks',
docs,
iterator=document_splitter(
docs.document,
separators='sentence,token_limit', # Split by sentence with token limit
limit=300, # Max 300 tokens per chunk
),
)
```
Inserting rows into \`chunks\`: 217 rows \[00:00, 42111.88 rows/s]
```python theme={"theme":{"light":"light-plus","dark":"dark-plus"}}
# View the chunks
chunks.select(chunks.text).head(5)
```
### Add semantic search
Create an embedding index on the chunks for similarity search:
```python theme={"theme":{"light":"light-plus","dark":"dark-plus"}}
# Add embedding index for semantic search
chunks.add_embedding_index(
column='text',
string_embed=sentence_transformer.using(model_id='all-MiniLM-L6-v2'),
)
```
### Search your documents
Use similarity search to find relevant chunks:
```python theme={"theme":{"light":"light-plus","dark":"dark-plus"}}
# Search for relevant chunks
query = 'market trends'
sim = chunks.text.similarity(string=query)
results = (
chunks.order_by(sim, asc=False)
.select(chunks.text, score=sim)
.limit(3)
)
results.collect()
```
## Explanation
**Separator options:**
You can combine separators: `separators='sentence,token_limit'`
**Chunk sizing:**
* `limit`: Maximum tokens per chunk (default: 500)
* `overlap`: Tokens to overlap between chunks (default: 0)
**New documents are processed automatically:**
When you insert new documents, chunks and embeddings are generated
without extra code.
## See also
* [Iterators
documentation](/platform/iterators)
* [RAG demo
notebook](/howto/use-cases/rag-demo)