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How To: Neo4j Data Import - Minimal Example

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How To: Neo4j Data Import - Minimal Example

The easiest way to import data from relational or legacy systems, like plain CSV files without headers, into Neo4j with Cypher and a graph model.

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We want to import data into Neo4j, but there are too many resources with a lot of information which makes it confusing.

Here is the minimal thing you need to know.

Imagine the data coming from the export of a relational or legacy system, just plain CSV files without headers (this time).

people.csv

1,"John" 10,"Jane" 234,"Fred" 4893,"Mark" 234943,"Anne"

friendships.csv

1,234 10,4893 234,1 4893,234943 234943,234 234943,1

Graph Model

Our graph Model would be very simple:

import data model.jpg

(p1:Person {userId:10, name:"Anne"})-[:KNOWS]->(p2:Person {userId:123,name:"John"})

Import with Neo4j Server and Cypher

  1. Download, install and start Neo4j Server.
  2. Open http://localhost:7474
  3. Run the following statements one by one:

I used http-urls here to run this as an interactive, live Graph Gist.

CREATE CONSTRAINT ON (p:Person) ASSERT p.userId IS UNIQUE;
LOAD CSV FROM "https://gist.githubusercontent.com/jexp/d8f251a948f5df83473a/raw/people.csv" AS row CREATE (:Person {userId: toInt(row[0]), name:row[1]});
USING PERIODIC COMMIT LOAD CSV FROM "https://gist.githubusercontent.com/jexp/d8f251a948f5df83473a/raw/friendships.csv" AS row MATCH (p1:Person {userId: toInt(row[0])}), (p2:Person {userId: toInt(row[1])}) CREATE (p1)-[:KNOWS]->(p2);

You can also use file-urls.
Best with absolute paths like file:/path/to/data.csv, on Windows use: file:c:/path/to/data.csv

If you want to find your people not only by id but also by name quickly, also run:

CREATE INDEX ON :Person(name);

For instance all second degree friends of “Anne” and on how many ways they can be reached.

MATCH (:Person {name:"Anne"})-[:KNOWS*2..2]-(p2) RETURN p2.name, count(*) as freq ORDER BY freq DESC;

Bulk Data Import

For tens of millions up to billions of rows.

Shutdown the server first!!

Create two additional header files:

people_header.csv

userId:ID,name

friendships_header.csv

:START_ID,:END_ID

Execute from the terminal:

path/to/neo/bin/neo4j-import --into path/to/neo/data/graph.db \ --nodes:Person people_header.csv,people.csv --relationships:KNOWS friendships_header.csv,friendships.csv

After starting your database again, run:

CREATE CONSTRAINT ON (p:Person) ASSERT p.userId IS UNIQUE;

Resources

Topics:
nosql ,tips and tricks ,neo4j ,database

Published at DZone with permission of Michael Hunger, DZone MVB. See the original article here.

Opinions expressed by DZone contributors are their own.

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