Class: Neo4j::Session

Inherits:
Object
  • Object
show all
Defined in:
lib/neo4j/session.rb

Defined Under Namespace

Classes: CypherError, InitializationError

Constant Summary collapse

@@current_session = 
nil
@@all_sessions = 
{}
@@factories = 
{}

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

._listeners ⇒ Object 



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# File 'lib/neo4j/session.rb', line 186

def _listeners
  @@listeners ||= []
  @@listeners
end

._notify_listeners(event, data) ⇒ Object 



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# File 'lib/neo4j/session.rb', line 192

def _notify_listeners(event, data)
  _listeners.shift.call(event, data) until _listeners.empty?
end

.add_listener(&listener) ⇒ Object 



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# File 'lib/neo4j/session.rb', line 181

def add_listener(&listener)
  _listeners << listener
end

.clear_listeners ⇒ Object 



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# File 'lib/neo4j/session.rb', line 176

def clear_listeners
  @@listeners = []
end

.create_session(db_type, endpoint_url, params = {}) ⇒ Object 



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# File 'lib/neo4j/session.rb', line 121

def create_session(db_type, endpoint_url, params = {})
  unless @@factories[db_type]
    fail InitializationError, "Can't connect to database '#{db_type}', available #{@@factories.keys.join(',')}"
  end
  @@factories[db_type].call(endpoint_url, params)
end

.current ⇒ Neo4j::Session

Returns the current session.

Returns:



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# File 'lib/neo4j/session.rb', line 129

def current
  @@current_session
end

.current! ⇒ Object

Returns the current session or raise an exception if no session is available



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# File 'lib/neo4j/session.rb', line 134

def current!
  fail 'No session, please create a session first with Neo4j::Session.open(:server_db) or :embedded_db' unless current
  current
end

.inspect ⇒ Object 



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# File 'lib/neo4j/session.rb', line 212

def inspect
  "Neo4j::Session available: #{@@factories && @@factories.keys}"
end

.named(name) ⇒ Object

Returns a session with given name or else raise an exception



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# File 'lib/neo4j/session.rb', line 145

def named(name)
  @@all_sessions[name] || fail("No session named #{name}.")
end

.on_next_session_available ⇒ Object

Registers a callback which will be called immediately if session is already available, or called when it later becomes available.



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# File 'lib/neo4j/session.rb', line 157

def on_next_session_available
  return yield(Neo4j::Session.current) if Neo4j::Session.current

  add_listener do |event, data|
    yield data if event == :session_available
  end
end

.open(db_type = :server_db, endpoint_url = nil, params = {}) ⇒ Object

Creates a new session to Neo4j. This will be the default session to be used unless there is already a session created (see #current and #set_current)

Examples:

A Neo4j Server session

Neo4j::Session.open(:server_db, 'http://localhost:7474', {basic_auth: {username: 'foo', password: 'bar'}})

Using a user defined Faraday HTTP connection

connection = Faraday.new do |b|
  # faraday config
end
Neo4j::Session.open(:server_db, 'http://localhost:7474', connection: connection)

A embedded Neo4j session

Neo4j::Session.open(:embedded_db, 'path/to/db')

Parameters:

  • db_type (defaults to: :server_db) —

    the type of database, e.g. :embedded_db, or :server_db

  • endpoint_url (String) (defaults to: nil) —

    The path to the server, either a URL or path to embedded DB

  • params (Hash) (defaults to: {}) —

    Additional configuration options

See Also:

  • Neo4j::Server::CypherSession#open for :server_db params


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# File 'lib/neo4j/session.rb', line 100

def open(db_type = :server_db, endpoint_url = nil, params = {})
  case db_type
  when :server_db then require 'neo4j-server'
  when :embedded_db then require 'neo4j-embedded'
  end

  validate_session_num!(db_type)
  name = params[:name]
  default = params[:default]
  [:name, :default].each { |k| params.delete(k) }
  register(create_session(db_type, endpoint_url, params), name, default)
end

.query(*args) ⇒ Object

See Also:



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# File 'lib/neo4j/session.rb', line 140

def query(*args)
  current!.query(*args)
end

.register(session, name = nil, default = nil) ⇒ Object 



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# File 'lib/neo4j/session.rb', line 197

def register(session, name = nil, default = nil)
  if default == true
    set_current(session)
  elsif default.nil?
    set_current(session) unless @@current_session
  end
  @@all_sessions[name] = session if name
  session
end

.register_db(db, &session_factory) ⇒ Object 



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# File 'lib/neo4j/session.rb', line 217

def register_db(db, &session_factory)
  puts "replace factory for #{db}" if @@factories[db]
  @@factories[db] = session_factory
end

.set_current(session) ⇒ Object

Sets the session to be used as default

Parameters:



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# File 'lib/neo4j/session.rb', line 151

def set_current(session)
  @@current_session = session
end

.unregister(session) ⇒ Object 



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# File 'lib/neo4j/session.rb', line 208

def unregister(session)
  @@current_session = nil if @@current_session == session
end

.user_agent_string ⇒ Object 



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# File 'lib/neo4j/session.rb', line 165

def user_agent_string
  gem, version = if defined?(::Neo4j::ActiveNode)
                   ['neo4j', ::Neo4j::VERSION]
                 else
                   ['neo4j-core', ::Neo4j::Core::VERSION]
                 end


  "#{gem}-gem/#{version} (https://github.com/neo4jrb/#{gem})"
end

.validate_session_num!(db_type) ⇒ Object 



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# File 'lib/neo4j/session.rb', line 114

def validate_session_num!(db_type)
  return unless current && db_type == :embedded_db
  fail InitializationError, 'Multiple sessions are not supported by Neo4j Embedded.'
end

Instance Method Details

#_query(*params) ⇒ Object

This method is abstract.

Same as #query but does not accept an DSL and returns the raw result from the database. Notice, it might return different values depending on which database is used, embedded or server.



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# File 'lib/neo4j/session.rb', line 76

def _query(*params)
  fail 'not implemented'
end

#auto_commit? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/neo4j/session.rb', line 35

def auto_commit?
  true # TODO
end

#begin_tx ⇒ Object

This method is abstract. 


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# File 'lib/neo4j/session.rb', line 40

def begin_tx
  fail 'not impl.'
end

#close ⇒ Object

This method is abstract. 


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# File 'lib/neo4j/session.rb', line 8

def close
  self.class.unregister(self)
end

#db_type ⇒ :embedded_db | :server_db

Returns:

  • (:embedded_db | :server_db) 


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# File 'lib/neo4j/session.rb', line 31

def db_type
  fail 'not impl.'
end

#query(options = {}) ⇒ Neo4j::Core::Query, Enumerable

Performs a cypher query. See Core::Query for more details, but basic usage looks like:

Examples:

Using cypher DSL

Neo4j::Session.query.match("(c:person)-[:friends]->(p:person)").where(c: {name: 'andreas'}).pluck(:p).first[:name]

Show the generated Cypher

Neo4j::Session.query..match("(c:person)-[:friends]->(p:person)").where(c: {name: 'andreas'}).return(:p).to_cypher

Use Cypher string instead of the cypher DSL

Neo4j::Session.query("MATCH (c:person)-[:friends]->(p:person) WHERE c.name = \"andreas\" RETURN p").first[:p][:name]

Returns:

  • (Neo4j::Core::Query, Enumerable) —

    return a Query object for DSL or a Enumerable if using raw cypher strings

See Also:



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# File 'lib/neo4j/session.rb', line 69

def query(options = {})
  fail 'not implemented, abstract'
end

#running ⇒ Object

This method is abstract.

Only for embedded database



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# File 'lib/neo4j/session.rb', line 26

def running
  fail 'not impl.'
end

#shutdown ⇒ Object

This method is abstract.

Only for embedded database



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# File 'lib/neo4j/session.rb', line 20

def shutdown
  fail 'not impl.'
end

#start ⇒ Object

This method is abstract.

Only for embedded database



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# File 'lib/neo4j/session.rb', line 14

def start
  fail 'not impl.'
end