lex-neo4j

Legion Extension for Neo4j graph database via the HTTP Cypher transaction API.

Installation

gem 'lex-neo4j'

Usage

client = Legion::Extensions::Neo4j::Client.new(
  url: 'http://localhost:7474',
  username: 'neo4j',
  password: 'your-password',
  database: 'neo4j'
)

# Raw Cypher
client.query('MATCH (n:Person) RETURN n LIMIT 10')
client.query('CREATE (n:Person {name: $name}) RETURN n', parameters: { name: 'Alice' })

# Nodes
client.find_nodes(label: 'Person', properties: { name: 'Alice' })
client.create_node(label: 'Person', properties: { name: 'Bob', age: 30 })
client.merge_node(label: 'Person', match_properties: { email: 'bob@example.com' }, on_create: { created_at: Time.now.to_s })
client.count_nodes(label: 'Person')
client.list_labels

# Relationships
client.create_relationship(from_id: node1_id, to_id: node2_id, type: 'KNOWS', properties: { since: 2020 })
client.neighbors(id: node_id, direction: :outgoing, type: 'KNOWS')
client.shortest_path(from_id: node1_id, to_id: node2_id)
client.list_relationship_types

# Indexes & Constraints
client.list_indexes
client.create_index(label: 'Person', properties: ['name', 'email'], name: 'idx_person_name_email')
client.create_uniqueness_constraint(label: 'Person', property: 'email', name: 'uniq_person_email')
client.create_existence_constraint(label: 'Person', property: 'name')

# Explicit Transactions
tx = client.begin_transaction
client.execute_in_transaction(transaction_url: tx[:location], statements: ['CREATE (n:Temp) RETURN n'])
client.commit_transaction(transaction_url: tx[:location])

# Administration
client.server_info
client.list_databases
client.list_procedures
client.call_procedure(name: 'dbms.components')

# Graph Data Science (requires GDS plugin)
client.project_graph(name: 'social', node_projection: 'Person', relationship_projection: 'KNOWS')
client.run_pagerank(graph_name: 'social')
client.run_louvain(graph_name: 'social')
client.run_node_similarity(graph_name: 'social')
client.drop_graph(name: 'social')

Read-Only Mode

client = Legion::Extensions::Neo4j::Client.new(
  url: 'http://localhost:7474',
  username: 'neo4j',
  password: 'pass',
  read_only: true
)

client.find_nodes(label: 'Person')  # works
client.create_node(label: 'Person') # raises ReadOnlyError

Runners

Runner	Purpose
Cypher	Raw query execution, multi-statement batches
Nodes	Node CRUD, merge, count, label listing
Relationships	Relationship CRUD, merge, traversal, shortest path
Indexes	Index and constraint management (range, fulltext, uniqueness, existence)
Transactions	Explicit transaction lifecycle
Admin	Server info, database management, procedures, functions
GraphDataScience	GDS graph projections and algorithms (PageRank, Louvain, similarity)

License

MIT