Using the Neo4jrb gem, is it possible to use one transaction across multiple blocks

Question

Using the neo4jrb/neo4j gem (8.x), I know it is possible to run multiple queries inside a single transaction like so

person = Person.find_by(id: person_id)

Neo4j::ActiveBase.run_transaction do |tx|
  person.update(name: 'New name')
  person.update(number: 1)
end

But it possible to open a transaction, and then use that same transaction across multiple blocks. Something like:

person = Person.find_by(id: person_id)

transaction = Neo4j::ActiveBase.new_transaction

transaction.run do |tx|
  person.update(name: 'New name')
end

transaction.run do |tx|
  person.update(number: 1)
end

transaction.close

The reason why this functionality is desirable is because I'm using Neo4jrb inside of a Trailblazer-Operation. The trailblazer operation is broken up into discrete steps which are themselves written as separate methods. I want several of the steps wrapped in a transaction, but, without monkey patching the operation, I don't have the ability to execute some steps inside one transaction block.

Thanks!

score 0 · Accepted Answer · answered Aug 16 '17 at 15:54

So it turns out that my problem has multiple solutions.

While it wasn't immediately apparent to me that this was the case, after a new transaction is created in Neo4jrb, any subsequent queries in that same session are automatically associated with the transaction as long as it remains open.

person = Person.find_by(id: person_id)

transaction = Neo4j::ActiveBase.new_transaction

one = person.update(name: 'New name')

two = person.update(number: 1)

transaction.close

In the above example, both one and two are committed as part of transaction. So this solves my problem.

Another solution to my problem, is that trailblazer-operation has a specific method for wrapping steps in a db transaction block, as documented on Trailblazer's website.

step Wrap ->(*, &block) { Sequel.transaction do block.call end } {
  step Model( Song, :new )
  step Contract::Build( constant: MyContract )
  step Contract::Validate( )
  step Contract::Persist( method: :sync )
}

In the above example, all of the step methods inside step Wrap are called within the scope of the Sequel.transaction block.

Using the Neo4jrb gem, is it possible to use one transaction across multiple blocks

1 Answers1