Ex4j

This library combines the power of Ecto with the Bolt protocol provided by Bolt Sips ♥️

You can use the whole ecto suite you love for validations and structures plus an elegant DSL to retrieve data from Neo4j.

All Ex4j.Node have Ecto.Schema, Ecto.Changeset and Ex4j.Cypher automatically imported for convenience.

Installation

The package can be installed by adding ex4j to your list of dependencies in mix.exs:

def deps do
  [
    {:ex4j, "~> 0.1.0"}
  ]
end

Add the connection settings

config :ex4j, Bolt,
  url: "bolt://localhost:7687",
  basic_auth: [username: "neo4j", password: "zEb0zryxK62NNRXKWxJKd7qeEFkO3mLIgcGwuUA4lvg"],
  pool_size: 10,
  ssl: false

The docs can be found at https://hexdocs.pm/ex4j.

Usage

All the entities you query must have a schema Node. like below associated in your code:

defmodule Node.User do
  use Ex4j.Node

  graph do
    field(:name, :string)
    field(:age, :integer)
    field(:email, :string)
  end
end

defmodule Node.Has do
  use Ex4j.Node

  graph do
    field(:date, :utc_datetime_usec)
  end
end

defmodule Node.Comment do
  use Ex4j.Node

  graph do
    field(:content, :string)
  end
end

The module you intend to use for queries must use Ex4j.Cypher:

defmodule App do
  use Ex4j.Cypher

  def execute do 
    match(Node.User, as: :u)
    |> return(:u)
    |> run()
  end
end

  iex> App.execute()
  {:ok, [
    %{"u" => %Node.User{uuid: nil, name: "Tiago", age: 38, email: nil}},
    %{"u" => %Node.User{uuid: nil, name: "Davi", age: 35, email: nil}}
  ]}

defmodule App do
  use Ex4j.Cypher

  def execute do 
   match(Node.User, as: :u)
    |> vertex(Node.Comment, as: :c)
    |> edge(Node.Has, as: :h, from: :u, to: :c, type: :out)
    |> where(:u, "u.age IN [35,38] AND u.name CONTAINS 'Ti'")
    |> where(:c, "c.content CONTAINS 'Article'")
    |> where(:h, "h.date > date('2023-12-15')")
    |> return(:u)
    |> return(:c)
    |> run()
  end
end

 iex> User.execute()
 {:ok, [
    %{
      "c" => %Node.Comment{uuid: nil, content: "Tiago's Comment"},
      "u" => %Node.User{uuid: nil, name: "Tiago", age: 38, email: nil}
    },
    %{
      "c" => %Node.Comment{uuid: nil, content: "Davi's Comment"},
      "u" => %Node.User{uuid: nil, name: "Davi", age: 35, email: nil}
    }
 ]}

defmodule App do
  use Ex4j.Cypher

  def execute do 
    match(Node.User, as: :u)
    |> edge(Node.Has, as: :h, from: :u, to: :c, type: :out)
    |> vertex(Node.Comment, as: :c)
    |> return(:h)
    |> run()
  end
end

 iex> User.execute()
 {:ok, [
    %{"h" => %Node.Has{uuid: nil, role: "Tiago's Role"}},
    %{"h" => %Node.Has{uuid: nil, role: "Davi's Role"}}
 ]}

defmodule App do
  use Ex4j.Cypher

  def execute do 
    match(Node.User, as: :u)
    |> edge(Node.Has, as: :h, from: :u, to: :c, type: :out)
    |> vertex(Node.Comment, as: :c)
    |> return(:u, [:name])
    |> return(:c, [:content])
    |> run()
  end
end

iex> User.execute()
{:ok,[
    {"c" => %{"content" => "Tiago's Comment"}, "u" => %{"name" => "Tiago"}},
    %{"c" => %{"content" => "Davi's Comment"}, "u" => %{"name" => "Davi"}}
]}

defmodule App do
  use Ex4j.Cypher

  def execute do 
    match(Node.User, as: :u)
    |> edge(Node.Has, as: :h, from: :u, to: :c, type: :out)
    |> vertex(Node.Comment, as: :c)
    |> return(:u, [:name])
    |> return(:c, [:content])
    |> cypher()
  end
end

  iex> User.execute()
  "MATCH (u:User)-[h:Has]->(c:Comment)\nRETURN c.content,u.name"

You can always execute a query directly like so:

defmodule App do
  use Ex4j.Cypher

  def execute do
    query = 
    """
      MATCH (n:Comment) 
      RETURN n 
      LIMIT 25
    """

    run(query)
  end
end

  iex> App.execute()
  {:ok,
  %Bolt.Sips.Response{
   results: [
     %{
       "n" => %Bolt.Sips.Types.Node{
         id: 2,
         properties: %{"text" => "Tiago's Comment"},
         labels: ["Comment"]
       }
     },
     %{
       "n" => %Bolt.Sips.Types.Node{
         id: 3,
         properties: %{"content" => "Davi's Comment"},
         labels: ["Comment"]
       }
     },
   ],
   fields: ["n"],
   records: [
     [
       %Bolt.Sips.Types.Node{
         id: 2,
         properties: %{"text" => "Tiago's Comment"},
         labels: ["Comment"]
       }
     ],
     [
       %Bolt.Sips.Types.Node{
         id: 3,
         properties: %{"content" => "Davi's Comment"},
         labels: ["Comment"]
       }
     ]
   ],
   plan: nil,
   notifications: [],
   stats: [],
   profile: nil,
   type: "r",
   bookmark: "FB:kcwQOoduCuitRfejxXkLly0aBBiQ"
 }}

Plans

• Add support for migrations
• Add suport for more Cypher clauses like: CREATE, SKIP

License

Ex4j source code is released under Apache License 2.0.

Check NOTICE and LICENSE files for more information.