update rag tutorial

cookbook/pocketflow-rag/README.md

@@ -4,6 +4,7 @@ This project demonstrates a simplified RAG system that retrieves relevant docume
 
 ## Features
 
+- Document chunking for better retrieval granularity
 - Simple vector-based document retrieval
 - Two-stage pipeline (offline indexing, online querying)
 - FAISS-powered similarity search
@@ -57,6 +58,7 @@ The magic happens through a two-stage pipeline implemented with PocketFlow:
 ```mermaid
 graph TD
     subgraph OfflineFlow[Offline Document Indexing]
+        ChunkDocs[ChunkDocumentsNode] --> EmbedDocs[EmbedDocumentsNode]
         EmbedDocs[EmbedDocumentsNode] --> CreateIndex[CreateIndexNode]
     end
     
@@ -66,14 +68,19 @@ graph TD
 ```
 
 Here's what each part does:
-1. **EmbedDocumentsNode**: Converts documents into vector representations
-2. **CreateIndexNode**: Creates a searchable FAISS index from embeddings
-3. **EmbedQueryNode**: Converts user query into the same vector space
-4. **RetrieveDocumentNode**: Finds the most similar document using vector search
+1. **ChunkDocumentsNode**: Splits documents into smaller chunks for more granular retrieval
+2. **EmbedDocumentsNode**: Converts document chunks into vector representations
+3. **CreateIndexNode**: Creates a searchable FAISS index from embeddings
+4. **EmbedQueryNode**: Converts user query into the same vector space
+5. **RetrieveDocumentNode**: Finds the most similar document chunk using vector search
 
 ## Example Output
 
 ```
+==================================================
+PocketFlow RAG Document Retrieval
+==================================================
+✅ Created 5 chunks from 5 documents
 ✅ Created 5 document embeddings
 🔍 Creating search index...
 ✅ Index created with 5 vectors
@@ -88,4 +95,4 @@ Here's what each part does:
 - [`main.py`](./main.py): Main entry point for running the RAG demonstration
 - [`flow.py`](./flow.py): Configures the flows that connect the nodes
 - [`nodes.py`](./nodes.py): Defines the nodes for document processing and retrieval
-- [`utils.py`](./utils.py): Utility functions including the embedding function
+- [`utils.py`](./utils.py): Utility functions including chunking and embedding functions

cookbook/pocketflow-rag/flow.py

@@ -1,12 +1,13 @@
 from pocketflow import Flow
-from nodes import EmbedDocumentsNode, CreateIndexNode, EmbedQueryNode, RetrieveDocumentNode
+from nodes import EmbedDocumentsNode, CreateIndexNode, EmbedQueryNode, RetrieveDocumentNode, ChunkDocumentsNode
 
 def get_offline_flow():
     # Create offline flow for document indexing
+    chunk_docs_node = ChunkDocumentsNode()
     embed_docs_node = EmbedDocumentsNode()
     create_index_node = CreateIndexNode()
-    embed_docs_node >> create_index_node
-    offline_flow = Flow(start=embed_docs_node)
+    chunk_docs_node >> embed_docs_node >> create_index_node
+    offline_flow = Flow(start=chunk_docs_node)
     return offline_flow
 
 def get_online_flow():

cookbook/pocketflow-rag/nodes.py

@@ -1,9 +1,31 @@
 from pocketflow import Node, Flow, BatchNode
 import numpy as np
 import faiss
-from utils import get_embedding, get_openai_embedding
+from utils import get_embedding, get_openai_embedding, fixed_size_chunk
 
 # Nodes for the offline flow
+class ChunkDocumentsNode(BatchNode):
+    def prep(self, shared):
+        """Read texts from shared store"""
+        return shared["texts"]
+    
+    def exec(self, text):
+        """Chunk a single text into smaller pieces"""
+        return fixed_size_chunk(text)
+    
+    def post(self, shared, prep_res, exec_res_list):
+        """Store chunked texts in the shared store"""
+        # Flatten the list of lists into a single list of chunks
+        all_chunks = []
+        for chunks in exec_res_list:
+            all_chunks.extend(chunks)
+        
+        # Replace the original texts with the flat list of chunks
+        shared["texts"] = all_chunks
+        
+        print(f"✅ Created {len(all_chunks)} chunks from {len(prep_res)} documents")
+        return "default"
+    
 class EmbedDocumentsNode(BatchNode):
     def prep(self, shared):
         """Read texts from shared store and return as an iterable"""

cookbook/pocketflow-rag/utils.py

@@ -41,6 +41,11 @@ def get_openai_embedding(text):
     # Convert to numpy array for consistency with other embedding functions
     return np.array(embedding, dtype=np.float32)
 
+def fixed_size_chunk(text, chunk_size=2000):
+    chunks = []
+    for i in range(0, len(text), chunk_size):
+        chunks.append(text[i : i + chunk_size])
+    return chunks
 
 if __name__ == "__main__":
     # Test the embedding function