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RAG and Vector Databases

RAG grounds LLMs in real-world data, eliminating hallucinations and enabling knowledge-intensive applications. Full RAG stack: vector storage, retrieval engines, graph RAG, document parsing, and embedding models.

Vector DB Graph RAG Embeddings Document Parsing

Vector Databases

Name Description Links
Milvus Cloud-native, distributed vector database for billion-scale similarity search. Most scalable open-source vector DB. 44k+ stars. milvus.io
Qdrant High-performance vector search engine in Rust. Dense + sparse vectors, hybrid search, payload filtering, quantization. 30k+ stars. qdrant.tech
Weaviate AI-native vector database with GraphQL API, built-in vectorization, hybrid search, and generative search modules. 16k+ stars. weaviate.io
Chroma AI-native open-source embedding database. Extremely easy to start, built-in embedding functions. 16k+ stars. trychroma.com
pgvector PostgreSQL extension for vector similarity search. HNSW + IVFFlat indexes. Game-changer for Postgres users. 14k+ stars. GitHub
LanceDB Serverless vector database built on Lance columnar format. Embedded, multimodal, full-text + vector hybrid search. lancedb.com
Meilisearch Lightning-fast search engine API with AI-powered hybrid search (full-text + vector). 57k+ stars. meilisearch.com
Vespa Yahoo's battle-tested big data serving engine. ANN + lexical hybrid, tensor expressions, complex ML ranking. vespa.ai
Pinecone Managed vector database for high-performance vector search at scale. Docs
Zilliz Cloud-native vector database service (managed Milvus). zilliz.com
Turbopuffer Serverless vector database using object storage (S3) for cost-efficient large-scale search. Docs

RAG Engines & Platforms

Name Description Links
RAGFlow Leading open-source RAG engine with vision-based document parsing (tables, figures, layouts). Multi-recall: vector + full-text + knowledge graph. 78k+ stars. ragflow.io
AnythingLLM All-in-one AI app with RAG, agents, MCP support. Use any LLM, any document, any vector database. Privacy-first. 58k+ stars. useanything.com
Kotaemon Open-source RAG document QA tool with chat UI, graph RAG, multi-modal support, and citation highlighting. 22k+ stars. GitHub
Pathway LLM App Ready-to-run cloud templates for RAG and AI pipelines with live data sync (Sharepoint, S3, Kafka, Postgres). 60k+ stars. pathway.com
Cognee Memory management for AI agents and apps. Builds knowledge graphs from documents for reasoning-based RAG. 15k+ stars. cognee.ai
R2R (SciPhi) Production RAG engine with hybrid search, knowledge graph building (Neo4j), ingestion pipelines, and REST API. Docs

Graph RAG

Name Description Links
Microsoft GraphRAG Landmark Graph-based RAG: extracts knowledge graphs from documents, performs global queries via community summaries. 32k+ stars. Paper, Docs
LightRAG Faster, simpler alternative to GraphRAG. Dual-level retrieval (entity + thematic) with incremental knowledge graph updates. 15k+ stars. GitHub
PageIndex Document index for vectorless, reasoning-based RAG. Bypasses traditional embedding for reasoning-first retrieval. 25k+ stars. GitHub
Neo4j GraphRAG Official Neo4j library for GraphRAG pipelines. KG construction, hybrid retrieval (vector + Cypher). Docs

Document Parsing for RAG

Name Description Links
Docling IBM's fast document conversion: PDFs with layout understanding, table recognition (TableFormer), figure extraction. 20k+ stars. Docs
Unstructured Document parsing ETL for RAG. Extracts from PDFs, DOCX, HTML, images, and 30+ formats. 10k+ stars. unstructured.io
PaddleOCR Turn any PDF or image into structured data for AI. Supports 100+ languages. 75k+ stars. GitHub

Advanced RAG Techniques

Technique Description Links
Self-RAG LLMs that reflect on retrieval decisions using special tokens. Adaptive retrieval — only retrieve when needed. Paper, Code
CRAG (Corrective RAG) Adds retrieval evaluator + correction mechanism. Falls back to web search if retrieved docs are irrelevant. Paper
ColPali (Visual RAG) Revolutionary: indexes documents as images using vision-language models, eliminating OCR failures entirely. Paper, Code
HippoRAG Neurobiologically-inspired RAG using knowledge graphs mimicking hippocampal memory for multi-hop reasoning. Code
RAG Techniques Guide Comprehensive tutorial repository showcasing 20+ advanced RAG techniques with notebooks. 27k+ stars. GitHub

Embedding Models (2025-2026)

Model Provider Key Notes Links
text-embedding-3-large OpenAI 3072 dims (Matryoshka), strong general performance. Docs
embed-v4.0 Cohere Multimodal (text+image), 128K context, 100+ languages. Docs
voyage-3 Voyage AI Top MTEB scores (esp. code/finance/law), 32K context. Anthropic-backed. Docs
NV-Embed-v2 NVIDIA #1 MTEB overall at release. Decoder-only LLM architecture. 4096 dims. HuggingFace
nomic-embed-text-v1.5 Nomic AI Fully open (weights + data + code). Matryoshka dimensions. 8K context. HuggingFace
jina-embeddings-v3 Jina AI Task-specific LoRA adapters, Matryoshka, multilingual. HuggingFace
bge-m3 BAAI Multilingual (100 langs), multi-functionality: dense + sparse + ColBERT. HuggingFace
gte-Qwen2-7B-instruct Alibaba LLM-based embedding, top MTEB, instruction-tuned, 32K context. HuggingFace