Implementing RAG Systems

Quick-start guide for building production-grade RAG pipelines with LlamaIndex. This skill helps you set up the foundational components: document processing, embedding generation, and retrieval.

When to Use This Skill

• Building a new RAG pipeline from scratch
• Choosing optimal chunking strategy for your documents
• Selecting and configuring embedding models
• Implementing retrieval (vector, BM25, or hybrid search)
• Optimizing for specific use cases (Thai language, legal documents, product catalogs)
• Integrating with existing pipelines in

  src/

  or

  src-iLand/

Quick Decision Guide

Chunking Strategy

• Legal/Technical docs (like Thai land deeds) → 512-1024 tokens
• Narrative content → 1024-2048 tokens
• Q&A pairs → 256-512 tokens
• Rule of thumb: When halving chunk size, double

  similarity_top_k

Embedding Model Selection

• Cost-sensitive → HuggingFace bge-base-en-v1.5 with ONNX (3-7x faster, free)
• Quality-first → OpenAI text-embedding-3-small or JinaAI-base
• Multi-language (Thai) → Cohere embed-multilingual-v3.0
• Balanced → OpenAI or bge-large (open-source)

Retrieval Strategy

• Simple queries → Vector search
• Keyword-heavy → BM25
• Production systems → Hybrid (vector + BM25)
• Structured data → Metadata filtering
• Large doc sets (100+) → Document summary or recursive retrieval

Quick Start Patterns

Pattern 1: Standard RAG Setup (Vector Search)

from llama_index.core import VectorStoreIndex, SimpleDirectoryReader, Settings
from llama_index.core.node_parser import SentenceSplitter
from llama_index.embeddings.openai import OpenAIEmbedding

# Configure chunking
Settings.chunk_size = 1024
Settings.chunk_overlap = 20

# Configure embeddings
Settings.embed_model = OpenAIEmbedding(
    model="text-embedding-3-small",
    embed_batch_size=100
)

# Load and index documents
documents = SimpleDirectoryReader("./data").load_data()
index = VectorStoreIndex.from_documents(documents)

# Create query engine
query_engine = index.as_query_engine(similarity_top_k=5)
response = query_engine.query("Your question here")

Pattern 2: Multi-Language Setup (Thai Support)

from llama_index.core import VectorStoreIndex, SimpleDirectoryReader
from llama_index.embeddings.cohere import CohereEmbedding
from llama_index.core.node_parser import SentenceSplitter

# Use multilingual embeddings
embed_model = CohereEmbedding(
    model_name="embed-multilingual-v3.0",
    api_key="YOUR_COHERE_API_KEY"
)

# Configure chunking for Thai text
node_parser = SentenceSplitter(
    chunk_size=1024,
    chunk_overlap=50
)

# Load Thai documents
documents = SimpleDirectoryReader("./data").load_data()

# Create index with multilingual support
index = VectorStoreIndex.from_documents(
    documents,
    embed_model=embed_model,
    transformations=[node_parser]
)

query_engine = index.as_query_engine(similarity_top_k=5)

Pattern 3: Hybrid Search (Production-Ready)

from llama_index.core import VectorStoreIndex
from llama_index.retrievers.bm25 import BM25Retriever
from llama_index.core.retrievers import QueryFusionRetriever
import Stemmer

# Create vector index
index = VectorStoreIndex.from_documents(documents)
vector_retriever = index.as_retriever(similarity_top_k=10)

# Create BM25 retriever
bm25_retriever = BM25Retriever.from_defaults(
    docstore=index.docstore,
    similarity_top_k=10,
    stemmer=Stemmer.Stemmer("english")
)

# Combine with query fusion
hybrid_retriever = QueryFusionRetriever(
    [vector_retriever, bm25_retriever],
    similarity_top_k=5,
    mode="reciprocal_rerank",
    use_async=True
)

# Use in query engine
from llama_index.core.query_engine import RetrieverQueryEngine
query_engine = RetrieverQueryEngine.from_args(hybrid_retriever)

Pattern 4: Cost-Optimized Local Embeddings

from llama_index.embeddings.huggingface import HuggingFaceEmbedding
from llama_index.core import Settings

# Use local model with ONNX acceleration (3-7x faster)
Settings.embed_model = HuggingFaceEmbedding(
    model_name="BAAI/bge-base-en-v1.5",
    backend="onnx"  # Requires: pip install optimum[onnxruntime]
)

# Rest of the pipeline remains the same
index = VectorStoreIndex.from_documents(documents)

Your Codebase Integration

For

src/

Pipeline

Document Preprocessing (

src/02_prep_doc_for_embedding.py

):

• Add configurable chunking strategy
• Support multiple node parser types

Batch Embeddings (

src/09_enhanced_batch_embeddings.py

):

• Increase

  embed_batch_size

  to 100 for faster processing
• Consider local models to eliminate API costs

Basic Retrieval (

src/10_basic_query_engine.py

):

• Baseline vector search implementation
• Adjust

  similarity_top_k

  based on chunk size

For

src-iLand/

Pipeline (Thai Land Deeds)

Data Processing (

src-iLand/data_processing/

):

• Current chunk size: 1024 tokens (good for legal documents)
• Consider testing 512 with increased

  top_k

  for better precision

Embeddings (

src-iLand/docs_embedding/

):

• Current: OpenAI text-embedding-3-small
• Test: Cohere embed-multilingual-v3.0 for better Thai understanding

Retrieval (

src-iLand/retrieval/retrievers/

):

• Vector strategy: Baseline semantic search
• Hybrid strategy: Combines vector + BM25 for Thai queries
• Metadata strategy: Fast filtering (<50ms) on Thai geographic/legal metadata

Detailed References

Load these reference files when you need comprehensive details:

• reference-chunking.md: Complete chunking strategies guide

  • Node parser types and configurations
  • Chunk size optimization for different domains
  • Sentence-window and hierarchical patterns
  • Metadata preservation

• reference-embeddings.md: Embedding model selection and optimization

  • All supported models (OpenAI, Cohere, HuggingFace, JinaAI, Voyage)
  • Performance benchmarks (hit rate, MRR)
  • ONNX/OpenVINO optimization details
  • Multi-language support
  • Cost optimization strategies

• reference-retrieval-basics.md: Core retrieval patterns

  • Vector retrieval implementation
  • BM25 keyword search
  • Hybrid search (vector + BM25)
  • Metadata filtering
  • Configuration parameters and tuning

Common Workflows

Workflow 1: New RAG Pipeline Setup

• Step 1: Choose chunking strategy based on document type

  • Load

    reference-chunking.md

    for detailed guidance
  • Test with sample documents

• Step 2: Select embedding model

  • Load

    reference-embeddings.md

    for model comparison
  • Consider: cost, latency, language support
  • For Thai: use multilingual models

• Step 3: Implement basic vector retrieval

  • Start with simple VectorStoreIndex
  • Test with sample queries
  • Measure baseline performance

• Step 4: Optimize chunk size and top_k

  • Adjust based on query results
  • Balance precision vs recall

• Step 5: (Optional) Upgrade to hybrid search

  • Combine vector + BM25 for production quality

Workflow 2: Migrating from API to Local Embeddings

• Step 1: Choose local model (see

  reference-embeddings.md

  )
  • Recommended: BAAI/bge-base-en-v1.5

• Step 2: Install optimization backend

  pip install optimum[onnxruntime]
  

• Step 3: Update embedding configuration

  Settings.embed_model = HuggingFaceEmbedding(
      model_name="BAAI/bge-base-en-v1.5",
      backend="onnx"
  )
  

• Step 4: Re-index all documents

  • CRITICAL: Must re-embed with new model
  • Use caching to avoid redundant work

• Step 5: Validate retrieval quality

  • Compare results with API embeddings
  • Measure latency improvement (3-7x faster expected)

Workflow 3: Thai Language RAG Setup

• Step 1: Use multilingual embedding model

  embed_model = CohereEmbedding(
      model_name="embed-multilingual-v3.0"
  )
  

• Step 2: Configure appropriate chunking

  • Test 512-1024 tokens for Thai text
  • Preserve Thai metadata

• Step 3: Implement hybrid search

  • Vector for semantic understanding
  • BM25 for exact Thai keyword matching

• Step 4: Add metadata filtering

  • จังหวัด (province), อำเภอ (district), ประเภท (type)
  • Enable fast filtering (<50ms)

• Step 5: Test with Thai queries

  • Validate Unicode handling
  • Check retrieval relevance

Key Reminders

Critical Requirements:

• Re-indexing: When changing embedding models, MUST re-index all data
• Model consistency: Identical models for indexing and querying
• Chunk size + top_k: Halving chunk size → double

  similarity_top_k

Best Practices:

• Start simple (vector search) → Add complexity as needed (hybrid, metadata)
• Test with representative queries before full indexing
• Use local models for cost optimization at scale
• Enable parallel loading (

  num_workers=10

  ) for 13x speedup

Performance Tips:

• Batch size: Set

  embed_batch_size=100

  for API calls
• Parallel loading: Use

  SimpleDirectoryReader(...).load_data(num_workers=10)

• Caching: Enable ingestion pipeline caching for faster re-runs

Next Steps

After implementing basic RAG:

• Optimize: Use

  optimizing-rag

  skill for reranking, caching, production deployment
• Evaluate: Use

  evaluating-rag

  skill to measure hit rate, MRR, and compare strategies