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---
name: rag-implementation
description: Build Retrieval-Augmented Generation (RAG) systems for AI applications with vector databases and semantic search. Use when implementing knowledge-grounded AI, building document Q&A systems, or integrating LLMs with external knowledge bases.
allowed-tools: Read, Write, Bash
category: ai-engineering
tags: [rag, vector-databases, embeddings, retrieval, semantic-search]
version: 1.0.0
---
# RAG Implementation
Build Retrieval-Augmented Generation systems that extend AI capabilities with external knowledge sources.
## Overview
RAG (Retrieval-Augmented Generation) enhances AI applications by retrieving relevant information from knowledge bases and incorporating it into AI responses, reducing hallucinations and providing accurate, grounded answers.
## When to Use
Use this skill when:
- Building Q&A systems over proprietary documents
- Creating chatbots with current, factual information
- Implementing semantic search with natural language queries
- Reducing hallucinations with grounded responses
- Enabling AI systems to access domain-specific knowledge
- Building documentation assistants
- Creating research tools with source citation
- Developing knowledge management systems
## Core Components
### Vector Databases
Store and efficiently retrieve document embeddings for semantic search.
**Key Options:**
- **Pinecone**: Managed, scalable, production-ready
- **Weaviate**: Open-source, hybrid search capabilities
- **Milvus**: High performance, on-premise deployment
- **Chroma**: Lightweight, easy local development
- **Qdrant**: Fast, advanced filtering
- **FAISS**: Meta's library, full control
### Embedding Models
Convert text to numerical vectors for similarity search.
**Popular Models:**
- **text-embedding-ada-002** (OpenAI): General purpose, 1536 dimensions
- **all-MiniLM-L6-v2**: Fast, lightweight, 384 dimensions
- **e5-large-v2**: High quality, multilingual
- **bge-large-en-v1.5**: State-of-the-art performance
### Retrieval Strategies
Find relevant content based on user queries.
**Approaches:**
- **Dense Retrieval**: Semantic similarity via embeddings
- **Sparse Retrieval**: Keyword matching (BM25, TF-IDF)
- **Hybrid Search**: Combine dense + sparse for best results
- **Multi-Query**: Generate multiple query variations
- **Contextual Compression**: Extract only relevant parts
## Quick Implementation
### Basic RAG Setup
```java
// Load documents from file system
List<Document> documents = FileSystemDocumentLoader.loadDocuments("/path/to/docs");
// Create embedding store
InMemoryEmbeddingStore<TextSegment> embeddingStore = new InMemoryEmbeddingStore<>();
// Ingest documents into the store
EmbeddingStoreIngestor.ingest(documents, embeddingStore);
// Create AI service with RAG capability
Assistant assistant = AiServices.builder(Assistant.class)
.chatModel(chatModel)
.chatMemory(MessageWindowChatMemory.withMaxMessages(10))
.contentRetriever(EmbeddingStoreContentRetriever.from(embeddingStore))
.build();
```
### Document Processing Pipeline
```java
// Split documents into chunks
DocumentSplitter splitter = new RecursiveCharacterTextSplitter(
500, // chunk size
100 // overlap
);
// Create embedding model
EmbeddingModel embeddingModel = OpenAiEmbeddingModel.builder()
.apiKey("your-api-key")
.build();
// Create embedding store
EmbeddingStore<TextSegment> embeddingStore = PgVectorEmbeddingStore.builder()
.host("localhost")
.database("postgres")
.user("postgres")
.password("password")
.table("embeddings")
.dimension(1536)
.build();
// Process and store documents
for (Document document : documents) {
List<TextSegment> segments = splitter.split(document);
for (TextSegment segment : segments) {
Embedding embedding = embeddingModel.embed(segment).content();
embeddingStore.add(embedding, segment);
}
}
```
## Implementation Patterns
### Pattern 1: Simple Document Q&A
Create a basic Q&A system over your documents.
```java
public interface DocumentAssistant {
String answer(String question);
}
DocumentAssistant assistant = AiServices.builder(DocumentAssistant.class)
.chatModel(chatModel)
.contentRetriever(retriever)
.build();
```
### Pattern 2: Metadata-Filtered Retrieval
Filter results based on document metadata.
```java
// Add metadata during document loading
Document document = Document.builder()
.text("Content here")
.metadata("source", "technical-manual.pdf")
.metadata("category", "technical")
.metadata("date", "2024-01-15")
.build();
// Filter during retrieval
EmbeddingStoreContentRetriever retriever = EmbeddingStoreContentRetriever.builder()
.embeddingStore(embeddingStore)
.embeddingModel(embeddingModel)
.maxResults(5)
.minScore(0.7)
.filter(metadataKey("category").isEqualTo("technical"))
.build();
```
### Pattern 3: Multi-Source Retrieval
Combine results from multiple knowledge sources.
```java
ContentRetriever webRetriever = EmbeddingStoreContentRetriever.from(webStore);
ContentRetriever documentRetriever = EmbeddingStoreContentRetriever.from(documentStore);
ContentRetriever databaseRetriever = EmbeddingStoreContentRetriever.from(databaseStore);
// Combine results
List<Content> allResults = new ArrayList<>();
allResults.addAll(webRetriever.retrieve(query));
allResults.addAll(documentRetriever.retrieve(query));
allResults.addAll(databaseRetriever.retrieve(query));
// Rerank combined results
List<Content> rerankedResults = reranker.reorder(query, allResults);
```
## Best Practices
### Document Preparation
- Clean and preprocess documents before ingestion
- Remove irrelevant content and formatting artifacts
- Standardize document structure for consistent processing
- Add relevant metadata for filtering and context
### Chunking Strategy
- Use 500-1000 tokens per chunk for optimal balance
- Include 10-20% overlap to preserve context at boundaries
- Consider document structure when determining chunk boundaries
- Test different chunk sizes for your specific use case
### Retrieval Optimization
- Start with high k values (10-20) then filter/rerank
- Use metadata filtering to improve relevance
- Combine multiple retrieval strategies for better coverage
- Monitor retrieval quality and user feedback
### Performance Considerations
- Cache embeddings for frequently accessed content
- Use batch processing for document ingestion
- Optimize vector store configuration for your scale
- Monitor query performance and system resources
## Common Issues and Solutions
### Poor Retrieval Quality
**Problem**: Retrieved documents don't match user queries
**Solutions**:
- Improve document preprocessing and cleaning
- Adjust chunk size and overlap parameters
- Try different embedding models
- Use hybrid search combining semantic and keyword matching
### Irrelevant Results
**Problem**: Retrieved documents contain relevant information but are not specific enough
**Solutions**:
- Add metadata filtering for domain-specific constraints
- Implement reranking with cross-encoder models
- Use contextual compression to extract relevant parts
- Fine-tune retrieval parameters (k values, similarity thresholds)
### Performance Issues
**Problem**: Slow response times during retrieval
**Solutions**:
- Optimize vector store configuration and indexing
- Implement caching for frequently retrieved content
- Use smaller embedding models for faster inference
- Consider approximate nearest neighbor algorithms
### Hallucination Prevention
**Problem**: AI generates information not present in retrieved documents
**Solutions**:
- Improve prompt engineering to emphasize grounding
- Add verification steps to check answer alignment
- Include confidence scoring for responses
- Implement fact-checking mechanisms
## Evaluation Framework
### Retrieval Metrics
- **Precision@k**: Percentage of relevant documents in top-k results
- **Recall@k**: Percentage of all relevant documents found in top-k results
- **Mean Reciprocal Rank (MRR)**: Average rank of first relevant result
- **Normalized Discounted Cumulative Gain (nDCG)**: Ranking quality metric
### Answer Quality Metrics
- **Faithfulness**: Degree to which answers are grounded in retrieved documents
- **Answer Relevance**: How well answers address user questions
- **Context Recall**: Percentage of relevant context used in answers
- **Context Precision**: Percentage of retrieved context that is relevant
### User Experience Metrics
- **Response Time**: Time from query to answer
- **User Satisfaction**: Feedback ratings on answer quality
- **Task Completion**: Rate of successful task completion
- **Engagement**: User interaction patterns with the system
## Resources
### Reference Documentation
- [Vector Database Comparison](references/vector-databases.md) - Detailed comparison of vector database options
- [Embedding Models Guide](references/embedding-models.md) - Model selection and optimization
- [Retrieval Strategies](references/retrieval-strategies.md) - Advanced retrieval techniques
- [Document Chunking](references/document-chunking.md) - Chunking strategies and best practices
- [LangChain4j RAG Guide](references/langchain4j-rag-guide.md) - Official implementation patterns
### Assets
- `assets/vector-store-config.yaml` - Configuration templates for different vector stores
- `assets/retriever-pipeline.java` - Complete RAG pipeline implementation
- `assets/evaluation-metrics.java` - Evaluation framework code
## Constraints and Limitations
1. **Token Limits**: Respect model context window limitations
2. **API Rate Limits**: Manage external API rate limits and costs
3. **Data Privacy**: Ensure compliance with data protection regulations
4. **Resource Requirements**: Consider memory and computational requirements
5. **Maintenance**: Plan for regular updates and system monitoring
## Security Considerations
- Secure access to vector databases and embedding services
- Implement proper authentication and authorization
- Validate and sanitize user inputs
- Monitor for abuse and unusual usage patterns
- Regular security audits and penetration testing

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package com.example.rag;
import dev.langchain4j.data.document.Document;
import dev.langchain4j.data.document.DocumentSplitter;
import dev.langchain4j.data.document.parser.TextDocumentParser;
import dev.langchain4j.data.document.splitter.RecursiveCharacterTextSplitter;
import dev.langchain4j.data.embedding.Embedding;
import dev.langchain4j.data.segment.TextSegment;
import dev.langchain4j.model.embedding.EmbeddingModel;
import dev.langchain4j.model.openai.OpenAiEmbeddingModel;
import dev.langchain4j.store.embedding.EmbeddingStore;
import dev.langchain4j.store.embedding.EmbeddingStoreIngestor;
import dev.langchain4j.store.embedding.inmemory.InMemoryEmbeddingStore;
import dev.langchain4j.store.embedding.pinecone.PineconeEmbeddingStore;
import dev.langchain4j.store.embedding.chroma.ChromaEmbeddingStore;
import dev.langchain4j.store.embedding.qdrant.QdrantEmbeddingStore;
import dev.langchain4j.data.document.loader.FileSystemDocumentLoader;
import dev.langchain4j.store.embedding.filter.Filter;
import dev.langchain4j.store.embedding.filter.MetadataFilterBuilder;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;
import java.util.Map;
import java.util.HashMap;
/**
* Complete RAG Pipeline Implementation
*
* This class provides a comprehensive implementation of a RAG (Retrieval-Augmented Generation)
* system with support for multiple vector stores and advanced retrieval strategies.
*/
public class RAGPipeline {
private final EmbeddingModel embeddingModel;
private final EmbeddingStore<TextSegment> embeddingStore;
private final DocumentSplitter documentSplitter;
private final RAGConfig config;
/**
* Configuration class for RAG pipeline
*/
public static class RAGConfig {
private String vectorStoreType = "chroma";
private String openAiApiKey;
private String pineconeApiKey;
private String pineconeEnvironment;
private String pineconeIndex = "rag-documents";
private String chromaCollection = "rag-documents";
private String chromaPersistPath = "./chroma_db";
private String qdrantHost = "localhost";
private int qdrantPort = 6333;
private String qdrantCollection = "rag-documents";
private int chunkSize = 1000;
private int chunkOverlap = 200;
private int embeddingDimension = 1536;
// Getters and setters
public String getVectorStoreType() { return vectorStoreType; }
public void setVectorStoreType(String vectorStoreType) { this.vectorStoreType = vectorStoreType; }
public String getOpenAiApiKey() { return openAiApiKey; }
public void setOpenAiApiKey(String openAiApiKey) { this.openAiApiKey = openAiApiKey; }
public String getPineconeApiKey() { return pineconeApiKey; }
public void setPineconeApiKey(String pineconeApiKey) { this.pineconeApiKey = pineconeApiKey; }
public String getPineconeEnvironment() { return pineconeEnvironment; }
public void setPineconeEnvironment(String pineconeEnvironment) { this.pineconeEnvironment = pineconeEnvironment; }
public String getPineconeIndex() { return pineconeIndex; }
public void setPineconeIndex(String pineconeIndex) { this.pineconeIndex = pineconeIndex; }
public String getChromaCollection() { return chromaCollection; }
public void setChromaCollection(String chromaCollection) { this.chromaCollection = chromaCollection; }
public String getChromaPersistPath() { return chromaPersistPath; }
public void setChromaPersistPath(String chromaPersistPath) { this.chromaPersistPath = chromaPersistPath; }
public String getQdrantHost() { return qdrantHost; }
public void setQdrantHost(String qdrantHost) { this.qdrantHost = qdrantHost; }
public int getQdrantPort() { return qdrantPort; }
public void setQdrantPort(int qdrantPort) { this.qdrantPort = qdrantPort; }
public String getQdrantCollection() { return qdrantCollection; }
public void setQdrantCollection(String qdrantCollection) { this.qdrantCollection = qdrantCollection; }
public int getChunkSize() { return chunkSize; }
public void setChunkSize(int chunkSize) { this.chunkSize = chunkSize; }
public int getChunkOverlap() { return chunkOverlap; }
public void setChunkOverlap(int chunkOverlap) { this.chunkOverlap = chunkOverlap; }
public int getEmbeddingDimension() { return embeddingDimension; }
public void setEmbeddingDimension(int embeddingDimension) { this.embeddingDimension = embeddingDimension; }
}
/**
* Constructor
*/
public RAGPipeline(RAGConfig config) {
this.config = config;
this.embeddingModel = createEmbeddingModel();
this.embeddingStore = createEmbeddingStore();
this.documentSplitter = createDocumentSplitter();
}
/**
* Create embedding model based on configuration
*/
private EmbeddingModel createEmbeddingModel() {
return OpenAiEmbeddingModel.builder()
.apiKey(config.getOpenAiApiKey())
.modelName("text-embedding-ada-002")
.build();
}
/**
* Create embedding store based on configuration
*/
private EmbeddingStore<TextSegment> createEmbeddingStore() {
switch (config.getVectorStoreType().toLowerCase()) {
case "pinecone":
return PineconeEmbeddingStore.builder()
.apiKey(config.getPineconeApiKey())
.environment(config.getPineconeEnvironment())
.index(config.getPineconeIndex())
.dimension(config.getEmbeddingDimension())
.build();
case "chroma":
return ChromaEmbeddingStore.builder()
.collectionName(config.getChromaCollection())
.persistDirectory(config.getChromaPersistPath())
.build();
case "qdrant":
return QdrantEmbeddingStore.builder()
.host(config.getQdrantHost())
.port(config.getQdrantPort())
.collectionName(config.getQdrantCollection())
.dimension(config.getEmbeddingDimension())
.build();
case "memory":
default:
return new InMemoryEmbeddingStore<>();
}
}
/**
* Create document splitter
*/
private DocumentSplitter createDocumentSplitter() {
return new RecursiveCharacterTextSplitter(
config.getChunkSize(),
config.getChunkOverlap()
);
}
/**
* Load documents from directory
*/
public List<Document> loadDocuments(String directoryPath) {
try {
Path directory = Paths.get(directoryPath);
List<Document> documents = FileSystemDocumentLoader.loadDocuments(directory);
// Add metadata to documents
for (Document document : documents) {
Map<String, Object> metadata = new HashMap<>(document.metadata().toMap());
metadata.put("loaded_at", System.currentTimeMillis());
metadata.put("source_directory", directoryPath);
// Update document metadata
document = Document.from(document.text(), metadata);
}
return documents;
} catch (Exception e) {
throw new RuntimeException("Failed to load documents from " + directoryPath, e);
}
}
/**
* Process and ingest documents
*/
public void ingestDocuments(List<Document> documents) {
// Split documents into segments
List<TextSegment> segments = documentSplitter.split(documents);
// Add additional metadata to segments
for (int i = 0; i < segments.size(); i++) {
TextSegment segment = segments.get(i);
Map<String, Object> metadata = new HashMap<>(segment.metadata().toMap());
metadata.put("segment_index", i);
metadata.put("total_segments", segments.size());
metadata.put("processed_at", System.currentTimeMillis());
segments.set(i, TextSegment.from(segment.text(), metadata));
}
// Ingest into embedding store
EmbeddingStoreIngestor.ingest(segments, embeddingStore);
System.out.println("Ingested " + documents.size() + " documents into " +
segments.size() + " segments");
}
/**
* Search documents with optional filtering
*/
public List<TextSegment> search(String query, int maxResults, Filter filter) {
Embedding queryEmbedding = embeddingModel.embed(query).content();
return embeddingStore.findRelevant(queryEmbedding, maxResults, filter);
}
/**
* Search documents with metadata filtering
*/
public List<TextSegment> searchWithMetadataFilter(String query, int maxResults,
Map<String, Object> metadataFilters) {
Filter filter = null;
if (metadataFilters != null && !metadataFilters.isEmpty()) {
MetadataFilterBuilder filterBuilder = new MetadataFilterBuilder();
for (Map.Entry<String, Object> entry : metadataFilters.entrySet()) {
String key = entry.getKey();
Object value = entry.getValue();
if (value instanceof String) {
filterBuilder = filterBuilder.metadata(key).isEqualTo((String) value);
} else if (value instanceof Number) {
filterBuilder = filterBuilder.metadata(key).isEqualTo(((Number) value).doubleValue());
}
// Add more type handling as needed
}
filter = filterBuilder.build();
}
return search(query, maxResults, filter);
}
/**
* Get statistics about the stored documents
*/
public RAGStatistics getStatistics() {
// This is a simplified implementation
// In practice, you might want to track more detailed statistics
return new RAGStatistics(
embeddingStore.getClass().getSimpleName(),
config.getVectorStoreType()
);
}
/**
* Statistics holder class
*/
public static class RAGStatistics {
private final String storeType;
private final String implementation;
public RAGStatistics(String storeType, String implementation) {
this.storeType = storeType;
this.implementation = implementation;
}
public String getStoreType() { return storeType; }
public String getImplementation() { return implementation; }
@Override
public String toString() {
return "RAGStatistics{" +
"storeType='" + storeType + '\'' +
", implementation='" + implementation + '\'' +
'}';
}
}
/**
* Example usage
*/
public static void main(String[] args) {
// Configure the pipeline
RAGConfig config = new RAGConfig();
config.setVectorStoreType("chroma"); // or "pinecone", "qdrant", "memory"
config.setOpenAiApiKey("your-openai-api-key");
config.setChunkSize(1000);
config.setChunkOverlap(200);
// Create pipeline
RAGPipeline pipeline = new RAGPipeline(config);
// Load documents
List<Document> documents = pipeline.loadDocuments("./documents");
// Ingest documents
pipeline.ingestDocuments(documents);
// Search for relevant content
List<TextSegment> results = pipeline.search("What is machine learning?", 5, null);
// Print results
for (int i = 0; i < results.size(); i++) {
TextSegment segment = results.get(i);
System.out.println("Result " + (i + 1) + ":");
System.out.println("Content: " + segment.text().substring(0, Math.min(200, segment.text().length())) + "...");
System.out.println("Metadata: " + segment.metadata());
System.out.println();
}
// Print statistics
System.out.println("Pipeline Statistics: " + pipeline.getStatistics());
}
}

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# Vector Store Configuration Templates
# This file contains configuration templates for different vector databases
# Chroma (Local/Development)
chroma:
type: chroma
settings:
persist_directory: "./chroma_db"
collection_name: "rag_documents"
host: "localhost"
port: 8000
# Recommended for: Development, small-scale applications
# Pros: Easy setup, local deployment, free
# Cons: Limited scalability, single-node only
# Pinecone (Cloud/Production)
pinecone:
type: pinecone
settings:
api_key: "${PINECONE_API_KEY}"
environment: "us-west1-gcp"
index_name: "rag-documents"
dimension: 1536
metric: "cosine"
pods: 1
pod_type: "p1.x1"
# Recommended for: Production applications, large-scale
# Pros: Managed service, scalable, fast
# Cons: Cost, requires internet connection
# Weaviate (Open-source/Cloud)
weaviate:
type: weaviate
settings:
url: "http://localhost:8080"
api_key: "${WEAVIATE_API_KEY}"
class_name: "Document"
text_key: "content"
vectorizer: "text2vec-openai"
module_config:
text2vec-openai:
model: "ada"
modelVersion: "002"
type: "text"
baseUrl: "https://api.openai.com/v1"
# Recommended for: Hybrid search, GraphQL API
# Pros: Open-source, hybrid search, flexible
# Cons: More complex setup
# Qdrant (Performance-focused)
qdrant:
type: qdrant
settings:
host: "localhost"
port: 6333
collection_name: "rag_documents"
vector_size: 1536
distance: "Cosine"
api_key: "${QDRANT_API_KEY}"
# Recommended for: Performance, advanced filtering
# Pros: Fast, good filtering, open-source
# Cons: Newer project, smaller community
# Milvus (Enterprise/Scale)
milvus:
type: milvus
settings:
host: "localhost"
port: 19530
collection_name: "rag_documents"
dimension: 1536
index_type: "IVF_FLAT"
metric_type: "COSINE"
nlist: 1024
# Recommended for: Enterprise, large-scale deployments
# Pros: High performance, distributed
# Cons: Complex setup, resource intensive
# FAISS (Local/Research)
faiss:
type: faiss
settings:
index_type: "IndexFlatL2"
dimension: 1536
save_path: "./faiss_index"
# Recommended for: Research, local processing
# Pros: Fast, local, no dependencies
# Cons: No persistence, limited features
# Common Configuration Parameters
common:
chunking:
chunk_size: 1000
chunk_overlap: 200
separators: ["\n\n", "\n", " ", ""]
embedding:
model: "text-embedding-ada-002"
batch_size: 100
max_retries: 3
timeout: 30
retrieval:
default_k: 5
similarity_threshold: 0.7
max_results: 20
performance:
cache_embeddings: true
cache_size: 1000
parallel_processing: true
batch_size: 50
# Environment Variables Template
# Copy this to .env file and fill in your values
environment:
OPENAI_API_KEY: "your-openai-api-key-here"
PINECONE_API_KEY: "your-pinecone-api-key-here"
PINECONE_ENVIRONMENT: "us-west1-gcp"
WEAVIATE_API_KEY: "your-weaviate-api-key-here"
QDRANT_API_KEY: "your-qdrant-api-key-here"

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# Document Chunking Strategies
## Overview
Document chunking is the process of breaking large documents into smaller, manageable pieces that can be effectively embedded and retrieved.
## Chunking Strategies
### 1. Recursive Character Text Splitter
**Method**: Split text based on character count, trying separators in order
**Use Case**: General purpose text splitting
**Advantages**: Preserves sentence and paragraph boundaries when possible
```python
from langchain.text_splitters import RecursiveCharacterTextSplitter
splitter = RecursiveCharacterTextSplitter(
chunk_size=1000,
chunk_overlap=200,
length_function=len,
separators=["\n\n", "\n", " ", ""] # Try these in order
)
chunks = splitter.split_documents(documents)
```
### 2. Token-Based Splitting
**Method**: Split based on token count rather than characters
**Use Case**: When working with token limits of language models
**Advantages**: Better control over context window usage
```python
from langchain.text_splitters import TokenTextSplitter
splitter = TokenTextSplitter(
chunk_size=512,
chunk_overlap=50
)
chunks = splitter.split_documents(documents)
```
### 3. Semantic Chunking
**Method**: Split based on semantic similarity
**Use Case**: When maintaining semantic coherence is important
**Advantages**: Chunks are more semantically meaningful
```python
from langchain.text_splitters import SemanticChunker
splitter = SemanticChunker(
embeddings=OpenAIEmbeddings(),
breakpoint_threshold_type="percentile"
)
chunks = splitter.split_documents(documents)
```
### 4. Markdown Header Splitter
**Method**: Split based on markdown headers
**Use Case**: Structured documents with clear hierarchical organization
**Advantages**: Maintains document structure and context
```python
from langchain.text_splitters import MarkdownHeaderTextSplitter
headers_to_split_on = [
("#", "Header 1"),
("##", "Header 2"),
("###", "Header 3"),
]
splitter = MarkdownHeaderTextSplitter(headers_to_split_on=headers_to_split_on)
chunks = splitter.split_documents(documents)
```
### 5. HTML Splitter
**Method**: Split based on HTML tags
**Use Case**: Web pages and HTML documents
**Advantages**: Preserves HTML structure and metadata
```python
from langchain.text_splitters import HTMLHeaderTextSplitter
headers_to_split_on = [
("h1", "Header 1"),
("h2", "Header 2"),
("h3", "Header 3"),
]
splitter = HTMLHeaderTextSplitter(headers_to_split_on=headers_to_split_on)
chunks = splitter.split_documents(documents)
```
## Parameter Tuning
### Chunk Size
- **Small chunks (200-400 tokens)**: More precise retrieval, but may lose context
- **Medium chunks (500-1000 tokens)**: Good balance of precision and context
- **Large chunks (1000-2000 tokens)**: More context, but less precise retrieval
### Chunk Overlap
- **Purpose**: Preserve context at chunk boundaries
- **Typical range**: 10-20% of chunk size
- **Higher overlap**: Better context preservation, but more redundancy
- **Lower overlap**: Less redundancy, but may lose important context
### Separators
- **Hierarchical separators**: Start with larger boundaries (paragraphs), then smaller (sentences)
- **Custom separators**: Add domain-specific separators for better results
- **Language-specific**: Adjust for different languages and writing styles
## Best Practices
1. **Preserve Context**: Ensure chunks contain enough surrounding context
2. **Maintain Coherence**: Keep semantically related content together
3. **Respect Boundaries**: Avoid breaking sentences or important phrases
4. **Consider Query Types**: Adapt chunking strategy to typical user queries
5. **Test and Iterate**: Evaluate different chunking strategies for your specific use case
## Evaluation Metrics
1. **Retrieval Quality**: How well chunks answer user queries
2. **Context Preservation**: Whether important context is maintained
3. **Chunk Distribution**: Evenness of chunk sizes
4. **Boundary Quality**: How natural chunk boundaries are
5. **Retrieval Efficiency**: Impact on retrieval speed and accuracy
## Advanced Techniques
### Adaptive Chunking
Adjust chunk size based on document structure and content density.
### Hierarchical Chunking
Create multiple levels of chunks for different retrieval scenarios.
### Query-Aware Chunking
Optimize chunk boundaries based on typical query patterns.
### Domain-Specific Splitting
Use specialized splitters for specific document types (legal, medical, technical).

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# Embedding Models Guide
## Overview
Embedding models convert text into numerical vectors that capture semantic meaning for similarity search in RAG systems.
## Popular Embedding Models
### 1. text-embedding-ada-002 (OpenAI)
- **Dimensions**: 1536
- **Type**: General purpose
- **Use Case**: Most applications requiring high quality embeddings
- **Performance**: Excellent balance of quality and speed
### 2. all-MiniLM-L6-v2 (Sentence Transformers)
- **Dimensions**: 384
- **Type**: Lightweight
- **Use Case**: Applications requiring fast inference
- **Performance**: Good quality, very fast
### 3. e5-large-v2
- **Dimensions**: 1024
- **Type**: High quality
- **Use Case**: Applications needing superior performance
- **Performance**: Excellent quality, multilingual support
### 4. Instructor
- **Dimensions**: Variable (768)
- **Type**: Task-specific
- **Use Case**: Domain-specific applications
- **Performance**: Can be fine-tuned for specific tasks
### 5. bge-large-en-v1.5
- **Dimensions**: 1024
- **Type**: State-of-the-art
- **Use Case**: Applications requiring best possible quality
- **Performance**: SOTA performance on benchmarks
## Selection Criteria
1. **Quality vs Speed**: Balance between embedding quality and inference speed
2. **Dimension Size**: Impact on storage and retrieval performance
3. **Domain**: Specific language or domain requirements
4. **Cost**: API costs vs local deployment
5. **Batch Size**: Throughput requirements
6. **Language**: Multilingual support needs
## Usage Examples
### OpenAI Embeddings
```python
from langchain.embeddings import OpenAIEmbeddings
embeddings = OpenAIEmbeddings()
vector = embeddings.embed_query("Your text here")
```
### Sentence Transformers
```python
from sentence_transformers import SentenceTransformer
model = SentenceTransformer('all-MiniLM-L6-v2')
vector = model.encode("Your text here")
```
### Hugging Face Models
```python
from langchain.embeddings import HuggingFaceEmbeddings
embeddings = HuggingFaceEmbeddings(
model_name="sentence-transformers/all-MiniLM-L6-v2"
)
```
## Optimization Tips
1. **Batch Processing**: Process multiple texts together for efficiency
2. **Model Quantization**: Reduce model size for faster inference
3. **Caching**: Cache embeddings for frequently used texts
4. **GPU Acceleration**: Use GPU for faster processing when available
5. **Model Selection**: Choose appropriate model size for your use case
## Evaluation Metrics
1. **Semantic Similarity**: How well embeddings capture meaning
2. **Retrieval Performance**: Quality of retrieved documents
3. **Speed**: Inference time per document
4. **Memory Usage**: RAM requirements for the model
5. **Cost**: API costs or infrastructure requirements

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# LangChain4j RAG Implementation Guide
## Overview
RAG (Retrieval-Augmented Generation) extends LLM knowledge by finding and injecting relevant information from your data into prompts before sending to the LLM.
## What is RAG?
RAG helps LLMs answer questions using domain-specific knowledge by retrieving relevant information to reduce hallucinations.
## RAG Flavors in LangChain4j
### 1. Easy RAG
Simplest way to start with minimal setup. Handles document loading, splitting, and embedding automatically.
### 2. Core RAG APIs
Modular components including:
- Document
- TextSegment
- EmbeddingModel
- EmbeddingStore
- DocumentSplitter
### 3. Advanced RAG
Complex pipelines supporting:
- Query transformation
- Multi-source retrieval
- Re-ranking with components like QueryTransformer and ContentRetriever
## RAG Stages
### 1. Indexing
Pre-process documents for efficient search
### 2. Retrieval
Find relevant content based on user queries
## Core Components
### Documents with metadata
Structured representation of your content with associated metadata for filtering and context.
### Text segments (chunks)
Smaller, manageable pieces of documents that are embedded and stored in vector databases.
### Embedding models
Convert text segments into numerical vectors for similarity search.
### Embedding stores (vector databases)
Store and efficiently retrieve embedded text segments.
### Content retrievers
Find relevant content based on user queries.
### Query transformers
Transform and optimize user queries for better retrieval.
### Content aggregators
Combine and rank retrieved content.
## Advanced Features
- Query transformation and routing
- Multiple retrievers for different data sources
- Re-ranking models for improved relevance
- Metadata filtering for targeted retrieval
- Parallel processing for performance
## Implementation Example (Easy RAG)
```java
// Load documents
List<Document> documents = FileSystemDocumentLoader.loadDocuments("/path/to/docs");
// Create embedding store
InMemoryEmbeddingStore<TextSegment> embeddingStore = new InMemoryEmbeddingStore<>();
// Ingest documents
EmbeddingStoreIngestor.ingest(documents, embeddingStore);
// Create AI service
Assistant assistant = AiServices.builder(Assistant.class)
.chatModel(chatModel)
.chatMemory(MessageWindowChatMemory.withMaxMessages(10))
.contentRetriever(EmbeddingStoreContentRetriever.from(embeddingStore))
.build();
```
## Best Practices
1. **Document Preparation**: Clean and structure documents before ingestion
2. **Chunk Size**: Balance between context preservation and retrieval precision
3. **Metadata Strategy**: Include relevant metadata for filtering and context
4. **Embedding Model Selection**: Choose models appropriate for your domain
5. **Retrieval Strategy**: Select appropriate k values and filtering criteria
6. **Evaluation**: Continuously evaluate retrieval quality and answer accuracy

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# Advanced Retrieval Strategies
## Overview
Different retrieval approaches for finding relevant documents in RAG systems, each with specific strengths and use cases.
## Retrieval Approaches
### 1. Dense Retrieval
**Method**: Semantic similarity via embeddings
**Use Case**: Understanding meaning and context
**Example**: Finding documents about "machine learning" when query is "AI algorithms"
```python
from langchain.vectorstores import Chroma
vectorstore = Chroma.from_documents(chunks, embeddings)
results = vectorstore.similarity_search("query", k=5)
```
### 2. Sparse Retrieval
**Method**: Keyword matching (BM25, TF-IDF)
**Use Case**: Exact term matching and keyword-specific queries
**Example**: Finding documents containing specific technical terms
```python
from langchain.retrievers import BM25Retriever
bm25_retriever = BM25Retriever.from_documents(chunks)
bm25_retriever.k = 5
results = bm25_retriever.get_relevant_documents("query")
```
### 3. Hybrid Search
**Method**: Combine dense + sparse retrieval
**Use Case**: Balance between semantic understanding and keyword matching
```python
from langchain.retrievers import BM25Retriever, EnsembleRetriever
# Sparse retriever (BM25)
bm25_retriever = BM25Retriever.from_documents(chunks)
bm25_retriever.k = 5
# Dense retriever (embeddings)
embedding_retriever = vectorstore.as_retriever(search_kwargs={"k": 5})
# Combine with weights
ensemble_retriever = EnsembleRetriever(
retrievers=[bm25_retriever, embedding_retriever],
weights=[0.3, 0.7]
)
```
### 4. Multi-Query Retrieval
**Method**: Generate multiple query variations
**Use Case**: Complex queries that can be interpreted in multiple ways
```python
from langchain.retrievers.multi_query import MultiQueryRetriever
# Generate multiple query perspectives
retriever = MultiQueryRetriever.from_llm(
retriever=vectorstore.as_retriever(),
llm=OpenAI()
)
# Single query → multiple variations → combined results
results = retriever.get_relevant_documents("What is the main topic?")
```
### 5. HyDE (Hypothetical Document Embeddings)
**Method**: Generate hypothetical documents for better retrieval
**Use Case**: When queries are very different from document style
```python
# Generate hypothetical document based on query
hypothetical_doc = llm.generate(f"Write a document about: {query}")
# Use hypothetical doc for retrieval
results = vectorstore.similarity_search(hypothetical_doc, k=5)
```
## Advanced Retrieval Patterns
### Contextual Compression
Compress retrieved documents to only include relevant parts
```python
from langchain.retrievers import ContextualCompressionRetriever
from langchain.retrievers.document_compressors import LLMChainExtractor
compressor = LLMChainExtractor.from_llm(llm)
compression_retriever = ContextualCompressionRetriever(
base_compressor=compressor,
base_retriever=vectorstore.as_retriever()
)
```
### Parent Document Retriever
Store small chunks for retrieval, return larger chunks for context
```python
from langchain.retrievers import ParentDocumentRetriever
from langchain.storage import InMemoryStore
store = InMemoryStore()
child_splitter = RecursiveCharacterTextSplitter(chunk_size=400)
parent_splitter = RecursiveCharacterTextSplitter(chunk_size=2000)
retriever = ParentDocumentRetriever(
vectorstore=vectorstore,
docstore=store,
child_splitter=child_splitter,
parent_splitter=parent_splitter
)
```
## Retrieval Optimization Techniques
### 1. Metadata Filtering
Filter results based on document metadata
```python
results = vectorstore.similarity_search(
"query",
filter={"category": "technical", "date": {"$gte": "2023-01-01"}},
k=5
)
```
### 2. Maximal Marginal Relevance (MMR)
Balance relevance with diversity
```python
results = vectorstore.max_marginal_relevance_search(
"query",
k=5,
fetch_k=20,
lambda_mult=0.5 # 0=max diversity, 1=max relevance
)
```
### 3. Reranking
Improve top results with cross-encoder
```python
from sentence_transformers import CrossEncoder
reranker = CrossEncoder('cross-encoder/ms-marco-MiniLM-L-6-v2')
candidates = vectorstore.similarity_search("query", k=20)
pairs = [[query, doc.page_content] for doc in candidates]
scores = reranker.predict(pairs)
reranked = sorted(zip(candidates, scores), key=lambda x: x[1], reverse=True)[:5]
```
## Selection Guidelines
1. **Query Type**: Choose strategy based on typical query patterns
2. **Document Type**: Consider document structure and content
3. **Performance Requirements**: Balance quality vs speed
4. **Domain Knowledge**: Leverage domain-specific patterns
5. **User Expectations**: Match retrieval behavior to user expectations

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# Vector Database Comparison and Configuration
## Overview
Vector databases store and efficiently retrieve document embeddings for semantic search in RAG systems.
## Popular Vector Database Options
### 1. Pinecone
- **Type**: Managed cloud service
- **Features**: Scalable, fast queries, managed infrastructure
- **Use Case**: Production applications requiring high availability
### 2. Weaviate
- **Type**: Open-source, hybrid search
- **Features**: Combines vector and keyword search, GraphQL API
- **Use Case**: Applications needing both semantic and traditional search
### 3. Milvus
- **Type**: High performance, on-premise
- **Features**: Distributed architecture, GPU acceleration
- **Use Case**: Large-scale deployments with custom infrastructure
### 4. Chroma
- **Type**: Lightweight, easy to use
- **Features**: Local deployment, simple API
- **Use Case**: Development and small-scale applications
### 5. Qdrant
- **Type**: Fast, filtered search
- **Features**: Advanced filtering, payload support
- **Use Case**: Applications requiring complex metadata filtering
### 6. FAISS
- **Type**: Meta's library, local deployment
- **Features**: High performance, CPU/GPU optimized
- **Use Case**: Research and applications needing full control
## Configuration Examples
### Pinecone Setup
```python
import pinecone
from langchain.vectorstores import Pinecone
pinecone.init(api_key="your-api-key", environment="us-west1-gcp")
index = pinecone.Index("your-index-name")
vectorstore = Pinecone(index, embeddings.embed_query, "text")
```
### Weaviate Setup
```python
import weaviate
from langchain.vectorstores import Weaviate
client = weaviate.Client("http://localhost:8080")
vectorstore = Weaviate(client, "Document", "content", embeddings)
```
### Chroma Local Setup
```python
from langchain.vectorstores import Chroma
vectorstore = Chroma(
collection_name="my_collection",
embedding_function=embeddings,
persist_directory="./chroma_db"
)
```
## Selection Criteria
1. **Scale**: Number of documents and expected query volume
2. **Performance**: Latency requirements and throughput needs
3. **Deployment**: Cloud vs on-premise preferences
4. **Features**: Filtering, hybrid search, metadata support
5. **Cost**: Budget constraints and operational overhead
6. **Maintenance**: Team expertise and available resources
## Best Practices
1. **Indexing Strategy**: Choose appropriate distance metrics (cosine, euclidean)
2. **Sharding**: Distribute data for large-scale deployments
3. **Monitoring**: Track query performance and system health
4. **Backups**: Implement regular backup procedures
5. **Security**: Secure access to sensitive data
6. **Optimization**: Tune parameters for your specific use case