Setup Japan Prefectures and Regions using neo4j and JavaScript

According to Wikipedia, Japan is divided into 47 prefectures（都道府県）, and these prefectures are grouped into eight regions （八大地方區分）.

First, we get the prefectures and regions from jp-prefecture package.

const jpPrefecture = require("jp-prefecture");

const regions = jpPrefecture.getAll("region");

const prefectures = jpPrefecture.getAll("pref");

After that, we can peek the region data:

[{
  id: 1,
  name: "北海道",
  kana: "ホッカイドウ",
  en: "hokkaido",
  neighbor: [2]
},
{
  id: 2,
  name: "東北",
  kana: "トウホク",
  en: "tohoku",
  neighbor: [1]
}

It means that hokkaido region (id 1) has a neighbor tohoku region(id 2), so we can link them together using the neighbor relationship.

We may also peek the prefectures data:

[{
  id:1,
  region:1,
  name:"北海道",
  short:"北海道",
  kana:"ホッカイドウ",
  en:"hokkaido",
  neighbor:[2]
},
  {
  id:2,
  region:2,
  name:"青森県",
  short:"青森",
  kana:"アオモリ",
  en:"aomori",
  neighbor:[1, 3, 5]
}]

It means that hokkaido prefecture (id 1) has a neigbor amori (id: 2), and amori has three neigbor (id 1 hokkaido, 3 iwate, 5 akita).

Neo4j

We create a cypher to loop all the regions, set name, kana and en property to the region node, and link the region to its neighbor. So the cypher is look like:

UNWIND $regions as region
MERGE (r:Region{id: region.id})
SET r.name = region.name
SET r.kana = region.kana
SET r.en = region.en
WITH r, region.neighbor as neighbor
UNWIND neighbor as id
MERGE (r2:Region{id: id})
MERGE (r)-[:NEIGHBOR]-(r2)

Just like the region, we loop all the prefectures, set name, short, kana and en properties in the prefecture node. After creating the prefectures, we create a relationship from the prefecture to the region. Also we set the neighbor relationship for the prefectures. So the cypher looks like

UNWIND $prefectures as prefecture
MERGE (p:Prefecture{id: prefecture.id})
SET p.name = prefecture.name
SET p.short = prefecture.short
SET p.kana = prefecture.kana
SET p.en = prefecture.en

WITH p, prefecture.region as region, prefecture.neighbor as neighbor
MATCH (r:Region{id: region})
MERGE (p)-[:REGION]->(r)

WITH p, neighbor
UNWIND neighbor as id
MERGE (p2:Prefecture{id: id})
MERGE (p)-[:NEIGHBOR]-(p2)

Neo4j JavaScript Driver

Basically, we connect to the neo4j database using the neo4j package, create driver and create session. NEO4J_URI, NEO4j_USERNAME and NEO4J_PASSWORD are in the .env file or environment variable.

const neo4j = require('neo4j')
const driver = neo4j.driver(process.env.NEO4J_URI, neo4j.auth.basic(process.env.NEO4j_USERNAME, process.env.NEO4J_PASSWORD))

const session = driver.session()

You may also import and configure them using dotenv package:

require('dotenv').config()

NEO4J_URI=
NEO4j_USERNAME=
NEO4J_PASSWORD=

In order to query in the database, we write the cypher and insert the params.

const cypher = ``
const params = {}
await session.run(cypher, params)

So for writing the regions:

const cypher = `
UNWIND $regions as region
MERGE (r:Region{id: region.id})
SET r.name = region.name
SET r.kana = region.kana
SET r.en = region.en
WITH r, region.neighbor as neighbor
UNWIND neighbor as id
MERGE (r2:Region{id: id})
MERGE (r)-[:NEIGHBOR]-(r2)
`

await session.run(cypher, { regions })

And for writing the prefectures:

const cypher2 = `
UNWIND $prefectures as prefecture
MERGE (p:Prefecture{id: prefecture.id})
SET p.name = prefecture.name
SET p.short = prefecture.short
SET p.kana = prefecture.kana
SET p.en = prefecture.en

WITH p, prefecture.region as region, prefecture.neighbor as neighbor
MATCH (r:Region{id: region})
MERGE (p)-[:REGION]->(r)

WITH p, neighbor
UNWIND neighbor as id
MERGE (p2:Prefecture{id: id})
MERGE (p)-[:NEIGHBOR]-(p2)
`

await session.run(cypher2, { prefectures })

Don’t forget to close the session.

Putting things together

require('dotenv').config()

async function main () {
    const jpPrefecture = require("jp-prefecture");

    const regions = jpPrefecture.getAll("region");

    const prefectures = jpPrefecture.getAll("pref");

    const neo4j = require('neo4j-driver')
    const driver = neo4j.driver(process.env.NEO4J_URI, neo4j.auth.basic(process.env.NEO4j_USERNAME, process.env.NEO4J_PASSWORD))

    const session = driver.session()

    try {
        const cypher = `
        UNWIND $regions as region
        MERGE (r:Region{id: region.id})
        SET r.name = region.name
        SET r.kana = region.kana
        SET r.en = region.en
        WITH r, region.neighbor as neighbor
        UNWIND neighbor as id
        MERGE (r2:Region{id: id})
        MERGE (r)-[:NEIGHBOR]-(r2)
    `

        await session.run(cypher, { regions })

        const cypher2 = `
        UNWIND $prefectures as prefecture
        MERGE (p:Prefecture{id: prefecture.id})
        SET p.name = prefecture.name
        SET p.short = prefecture.short
        SET p.kana = prefecture.kana
        SET p.en = prefecture.en

        WITH p, prefecture.region as region, prefecture.neighbor as neighbor
        MATCH (r:Region{id: region})
        MERGE (p)-[:REGION]->(r)

        WITH p, neighbor
        UNWIND neighbor as id
        MERGE (p2:Prefecture{id: id})
        MERGE (p)-[:NEIGHBOR]-(p2)
    `

        await session.run(cypher2, { prefectures })
        console.log('Finished')
    } finally {
        session.close()
        console.log('Session is closed')
        process.exit(0)
    }
}

main()

Result

We now have all regions:

And we also have all prefectures:

We may also get the full picture of Japan using the following cypher query:

MATCH (p:Prefecture)-[:REGION]->(r:Region)
RETURN p, r

If I want to know the region of Kyoto （京都府） Prefecture, I can use the following cypher query:

MATCH (p:Prefecture{en: 'kyoto'})-[:REGION]->(r:Region)
RETURN p, r

So the answer is kinki （近畿）.

Thoughts

I am really looking forward to travel to Japan one day, enjoying the Festival in Japan and playing maimai.

With neo4j, I can understand the relationship in Japan more easy.

btw, interesting thing that I find when I am writing this article.

Reference

1. wadackel/jp-prefecture - Github
2. motdotla/dotnev - Github
3. List of regions of Japan - Wikipedia
4. Prefectures of Japan - Wikipedia