Rails Neo4j如何在现有数据库中添加新字段

Question

class Invitation
  include Neo4j::ActiveNode
  property :email
end

This is Neo node Invitation node I can see it in the graph database. - If I add some new field in it, for existing nodes it will not reflect in the graph database - If I create a new node I can see it in graph database

So the question is if I have to add one field suppose

property :valid, type: Boolean, default: true

How can I add this so that I can see it in existing nodes in graph database???, same like we do in active record migrations

I have added field in Node

property :vish, type: Boolean, default: true

So when query

Invitation.where(vish: true).count ==> result 0

If I add new node Invitation.create(email: 'urvishh@gmail.com')

Then run query

Invitation.where(vish: true).count ==> result 1

This is exact issue I am getting

Answer 1

The short answer will be No : there is no way to Search for undeclared property values in persisted nodes.

Edited:

They added a Migration like behaviour for the gem that might fit your current needs.

http://neo4jrb.readthedocs.io/en/latest/Migrations.html

Discovery answer:

Nodes should be considered as documents that stores properties inside them. What we are dealing here is with an implementation of the Cypher Query and the Neo4j::ActiveNode that not only ignores the default values for properties.

This could be easily tested:

class User
  include Neo4j::ActiveNode

  property :name, type: String
  property :email, type: String, default: 'example@example.com'
end

Then create two nodes:

User.create(name: 'John', email: 'john@cena.com'
User.create(name: 'John')

We try to search for undeclared property values :

> User.where(title: 'Mr')
=> #<QueryProxy  CYPHER: "MATCH (result_user:`User`) WHERE (result_user.title = {result_user_title})">

We effectively call Cyper and get results, this means that the property declaration in model is not used at all in the Neo4j::ActiveNode#where

It means is only used to set and get properties, but ignored by the finders.

There might be workarounds, that are actually missing implementations in the Neo4j gem:

You can search by array of values in the Cyper connector, but is not parsing properly the values:

User.where(another_field: nil).count
CYPHER 39ms MATCH (result_user:`User`) WHERE (result_user.another_field IS NULL) RETURN count(result_user) AS result_user
=> 100
User.where(another_field: ['Something', nil]).count
 CYPHER 12ms MATCH (result_user:`User`) WHERE (result_user.another_field IN {result_user_another_field}) RETURN count(result_user) AS result_user | {:result_user_another_field=>["Something", nil]}
=> 0

As you can see in the last query, nil is passed literally. So you can't do this.

I've opened an Issue in the repository in your behalf, and linked this question in order to get a solution.