# Neo4j — The Leading Native Graph Database

> Neo4j is the leading native graph database, providing an ACID-compliant transactional backend for powerful graph queries via the Cypher query language. Used by NASA, eBay, Airbnb, and thousands of apps needing relationship-heavy data.

## Install

Save as a script file and run:

## Quick Use

```bash
# Docker
docker run -d --name neo4j -p 7474:7474 -p 7687:7687 \
  -e NEO4J_AUTH=neo4j/tokrepo12345 \
  -v neo4j-data:/data \
  neo4j:5-community

# Browser UI at http://localhost:7474
# Bolt protocol at bolt://localhost:7687
```

Cypher queries (via browser or cypher-shell):
```cypher
// Create nodes and relationships
CREATE (w:User { name: "William", role: "founder" })
CREATE (t:Product { name: "TokRepo" })
CREATE (w)-[:FOUNDED { year: 2025 }]->(t)

// Query: who founded what
MATCH (u:User)-[r:FOUNDED]->(p:Product)
RETURN u.name, p.name, r.year

// Find friends of friends (classic graph query)
MATCH (me:User { name: "William" })-[:KNOWS*2]-(fof:User)
WHERE fof.name <> "William"
RETURN DISTINCT fof.name

// Shortest path
MATCH path = shortestPath((a:City { name: "Shenzhen" })-[*]-(b:City { name: "Beijing" }))
RETURN path

// Indexes
CREATE INDEX user_name FOR (u:User) ON (u.name)
```

## Intro

Neo4j is the leading native graph database, providing a property graph model with ACID transactions, the declarative Cypher query language, and a high-performance graph storage engine. Founded in 2007 by Emil Eifrem. Used by NASA, Airbnb, eBay, Comcast, and thousands of apps where relationships between entities matter more than individual records.

- **Repo**: https://github.com/neo4j/neo4j
- **Stars**: 16K+
- **Language**: Java
- **License**: GPLv3 (Community) / commercial (Enterprise)

## What Neo4j Does

- **Property graph** — nodes, relationships, both with properties
- **Cypher** — SQL-like declarative query language (now ISO GQL standard)
- **Index-free adjacency** — constant-time traversal regardless of graph size
- **ACID transactions** — full consistency guarantees
- **Clustering** — Enterprise causal clustering for HA
- **Graph algorithms** — via Graph Data Science (GDS) library
- **Vector search** — Neo4j 5.11+ built-in vector indexes for RAG
- **GraphQL** — Neo4j GraphQL library to generate API

## Architecture

Native graph storage: nodes and relationships are first-class records on disk with direct pointers (index-free adjacency). Query engine compiles Cypher to an execution plan that walks the graph. Bolt binary protocol for driver communication.

## Self-Hosting

```yaml
# docker-compose.yml
version: "3"
services:
  neo4j:
    image: neo4j:5-community
    ports: ["7474:7474", "7687:7687"]
    volumes:
      - neo4j-data:/data
      - neo4j-logs:/logs
    environment:
      NEO4J_AUTH: neo4j/tokrepo12345
      NEO4J_server_memory_heap_max__size: 2G
      NEO4J_PLUGINS: "[\"apoc\", \"graph-data-science\"]"
volumes:
  neo4j-data:
  neo4j-logs:
```

## Key Features

- Native property graph storage
- Cypher query language
- ACID transactions
- Graph Data Science library (65+ algorithms)
- Vector indexes for AI/RAG
- Neo4j Browser UI
- Bolt binary protocol
- APOC stored procedures library
- Causal clustering (Enterprise)
- Fabric for multi-database queries

## Comparison

| Graph DB | Query Lang | Type | Storage |
|---|---|---|---|
| Neo4j | Cypher | Property graph | Native |
| ArangoDB | AQL | Multi-model | Native |
| JanusGraph | Gremlin | Property graph | Cassandra/HBase |
| TigerGraph | GSQL | Property graph | Native |
| Dgraph | DQL + GraphQL | RDF-like | Native |
| Memgraph | Cypher | Property graph | In-memory |
| NebulaGraph | nGQL | Property graph | Distributed |

## 常见问题 FAQ

**Q: 什么场景选图数据库？**
A: 社交网络、推荐系统、欺诈检测、知识图谱、依赖分析、身份认证链——任何以关系为核心的查询。

**Q: Cypher vs Gremlin？**
A: Cypher 声明式（SQL-like），Gremlin 命令式（像程序）。Cypher 更易读、已成为 ISO GQL 标准；Gremlin 更通用（任何 TinkerPop 图）。

**Q: 向量搜索？**
A: Neo4j 5.11+ 支持原生向量索引，可以把向量和图结构结合做 GraphRAG——图节点同时带 embedding。

## 来源与致谢 Sources

- Docs: https://neo4j.com/docs
- GitHub: https://github.com/neo4j/neo4j
- License: GPLv3 Community / commercial Enterprise

---
Source: https://tokrepo.com/en/workflows/0114235f-35f7-11f1-9bc6-00163e2b0d79
Author: Script Depot