Ruby neo4j-core mass processing data - ruby

Question

Has anyone used Ruby neo4j-core to mass process data? Specifically, I am looking at taking in about 500k lines from a relational database and insert them via something like:
Neo4j::Session.current.transaction.query
.merge(m: { Person: { token: person_token} })
.merge(i: { IpAddress: { address: ip, country: country,
city: city, state: state } })
.merge(a: { UserToken: { token: token } })
.merge(r: { Referrer: { url: referrer } })
.merge(c: { Country: { name: country } })
.break # This will make sure the query is not reordered
.create_unique("m-[:ACCESSED_FROM]->i")
.create_unique("m-[:ACCESSED_FROM]->a")
.create_unique("m-[:ACCESSED_FROM]->r")
.create_unique("a-[:ACCESSED_FROM]->i")
.create_unique("a-[:ACCESSED_FROM]->r")
.create_unique("i-[:IN]->c")
.exec
However doing this locally it takes hours on hundreds of thousands of events. So far, I have attempted the folloiwng:
Wrapping Neo4j::Connection in a ConnectionPool and multi-threading it - I did not see much speed improvements here.
Doing tx = Neo4j::Transaction.new and tx.close every 1000 events processed - looking at a TCP dump, I am not sure this actually does what I expected. It does the exact same requests, with the same frequency, but just has a different response.
With Neo4j::Transaction I see a POST every time the .query(...).exec is called:
Request: {"statements":[{"statement":"MERGE (m:Person{token: {m_Person_token}}) ...{"m_Person_token":"AAA"...,"resultDataContents":["row","REST"]}]}
Response: {"commit":"http://localhost:7474/db/data/transaction/868/commit","results":[{"columns":[],"data":[]}],"transaction":{"expires":"Tue, 10 May 2016 23:19:25 +0000"},"errors":[]}
With Non-Neo4j::Transactions I see the same POST frequency, but this data:
Request: {"query":"MERGE (m:Person{token: {m_Person_token}}) ... {"m_Person_token":"AAA"..."c_Country_name":"United States"}}
Response: {"columns" : [ ], "data" : [ ]}
(Not sure if that is intended behavior, but it looks like less data is transmitted via the Non-Neo4j::Transaction technique - highly possibly I am doing something incorrectly)
Some other ideas I had:
* Post process into a CSV, SCP up and then use the neo4j-import command line utility (although, that seems kinda hacky).
* Combine both of the techniques I tried above.
Has anyone else run into this / have other suggestions?

Answer 1

Ok!
So you're absolutely right. With neo4j-core you can only send one query at a time. With transactions all you're really getting is the ability to rollback. Neo4j does have a nice HTTP JSON API for transactions which allows you to send multiple Cypher requests in the same HTTP request, but neo4j-core doesn't currently support that (I'm working on a refactor for the next major version which will allow this). So there are a number of options:
You can submit your requests via raw HTTP JSON to the APIs. If you still want to use the Query API you can use the to_cypher and merge_params methods to get the cypher and params for that (merge_params is a private method currently, so you'd need to send(:merge_params))
You can load via CSV as you said. You can either
use the neo4j-import command which allows you to import very fast but requires you to put your CSV in a specific format, requires that you be creating a DB from scratch, and requires that you create indexes/constraints after the fact
use the LOAD CSV command which isn't as fast, but is still pretty fast.
You can use the neo4apis gem to build a DSL to import your data. The gem will create Cypher queries under the covers and will batch them for performance. See examples of the gem in use via neo4apis-twitter and neo4apis-github
If you are a bit more adventurous, you can use the new Cypher API in neo4j-core via the new_cypher_api branch on the GitHub repo. The README in that branch has some documentation on the API, but also feel free to drop by our Gitter chat room if you have questions on this or anything else.
If you're implementing a solution which is going to make queries like above where you have multiple MERGE clauses, you'll probably want to profile your queries to make sure that you are avoiding the eager (that post is a bit old and newer versions of Neo4j have alleviated some of the need for care, but you can still look for Eager in your PROFILE)
Also worth a look: Max De Marzi's post on Scaling Cypher Writes