如何在Neo4j ruby​​中的两个ActiveNode之间获取所有ActiveRel？

Question

Suppose we have

• Node: User
  • name : String
• Rel: Transaction
  • amount : Float

representing a simplized Bitcoin-like transaction, where a User sends coins to other Users. A Transaction has a property amount which shows how much coin you're sending to the to_node from from_node .

Then now I want to get all the transactions (either uni- or bi- directionally) between Alice and Bob. How can I do this?

# user.rb
has_many :out, :receivers, rel_class: :Transaction
has_many :in, :senders, rel_class: :Transaction


# Console
alice = User.find_by(name: "Alice")
bob = User.find_by(name: "Bob")

# I want to do something like this:
Transaction.between(from: alice, to: bob)

# or this:
alice.receivers.rel_where(to_node: bob)

I was surprised that the latter isn't acceptable. It includes bob directly into CYPHER.

Using Neo4jrb v8.0.0

Answer 1

I struggled and came to know I can do something like this:

alice.receivers.match_to(bob).pluck(:rel1)

With this we can get all the transactions sent from alice to bob , but I think it's not a good idea using the magical :rel1 here (which is available because it is automatically written in the CYPHER, and match_to returns a QueryProxy object: match_to )

But it is always not much encouraged to get just the Rels.
Relatively, we could

alice.receivers.match_to(bob).rel_where(amount: 1.0)   # Txs which amount are 1.0btc

and

alice.receivers.match_to(bob).each_rel.sum {|rel| rel.amount }   # All the sent money!

Note that you can't do this (somehow):

alice.receivers.match_to(bob).rel_where("rel1.amount < 10.0")

but can go-around with this:

query = alice.receivers.match_to(bob)          # create just the query
query.where("#{query.rel_var}.amount < 10.0")  # you can get `:rel1` by `rel_var`