flat2hier-graphql

Folds your JOINNED sql rows into a hierarchy of objects suitable for graphql response.

Get started

# Directly install from github
npm install --save git+https://github.com/Eyezon/flat2hier-graphql

How it works

flat2hier exposes a single function flat2hier(rows: Array<Object>, removeDollor: boolean): Array<Object> | Object

It takes an array of object and groups the objects by the follwing rules/convention and returns an array

Conventions

• For each row it splits each keys by _ say level_keys
• For each level key it adds an object or array for its value if it is not the last level_keys
• If a level_key starts with $ it adds an array, otherwise an object
• If level_key starts with $ and it has a child level key id it uses that id for subsequest row to insert in that same object in the array

Usage

Suppose we have two tables

TABLE 1 cars

Column Name	Datatype
id	INT
name	VARCHAR
license_no	VARCHAR

TABLE 2 drivers

Column Name	Datatype
id	INT
first_name	VARCHAR
last_name	VARCHAR

And every driver is assigned to zero or more cars using another table

TABLE 3 assigned_cars

Column Name	Datatype
car_id	INT
driver_id	INT

Now, Suppose we have a graphql schema like:

type Query {
    allCars(limit: Int): [Car]
    allDrivers(limit: Int): [Driver]
    driver(id: Int!): Driver
}

type Car {
    id: Int
    name: String
    licenseNo: String
}

type Driver {
    id: Int
    firstName: String
    lastName: String
    assignedCars: [Car]
}

For resolving allDrivers we can retrive all rows using sql join. But we need to group by driver and make an array of Car for same driver. flat2hier does this using some simple convention. e.g.

return database.queryAsync(`
    SELECT 
        d.id as \`$query_id\`,
        d.first_name as \`$query_firstName\`,
        d.last_name as \`$query_lastName\`,
        c.id as \`$query_$assignedCars_id\`,
        c.name as \`$query_$assignedCars_name\`,
        c.license_no as \`$query_$assignedCars_licenseNo\`,
    FROM drivers d
    JOIN assigned_cars asg_c ON asg_c.driver_id == d.id
    JOIN cars c ON asg_c.car_id == c.id
`).then(rows =>  flat2Hier(rows, true).query)

Convention used in flat2hier

flat2hier folds your array of row by

• Breaking each key/col name by _, and add the partial key into a object hierarchy(new object if at top level otherwise at current level). e.g. user_mailbox_certs_ssl128 => { user: { mailbox: { certs: { ssl128: <value> } } } }
• If a partial key(after splitting by _) starts with $ instead of adding a object for that key, it adds an array of object. e.g. $query_queryMetadata_sender_id => {$query: [ { queryMetadata: { sender: {id: <value>}} } ]}
• If it finds another partial key with starting with a $ and has a partial key child with name id it tries to find a object in the same key with matching id, if it finds one it creates object at current level and append in the array it just found.

For flat2hier 's usage see example/graphql.js file

Examples

const flat2hier = require('flat2hier')
const sqlRow = [ {
    $query_id: '13',
    $query_queryMetadata_id: '18',
    $query_queryMetadata_title: 'Title 1',
    $query_queryMetadata_sender_id: 's1',
    $query_queryMetadata_sender_name: 'debjyoti-in',
    $query_queryMetadata_sender_profileImageUrl: 'https://ppics.in/debjyoti-in-155x155.png',
    $query_queryMetadata_sender_phoneNo: '+91 xxxxxxxxxx',
    $query_queryMetadata_createdAt: 1502110354464,
    $query_queryMetadata_expiresAt: 1502110754464,
    $query_queryMetadata_lastChatAt: '13'
}]

flat2hier(sqlRow)
/* Returns: (note pass true as 2nd param to flat2hier if u want to remove the leading $ sign)
{
  "$query": [
    {
      "id": "13",
      "queryMetadata": {
        "id": "18",
        "title": "Title 1",
        "sender": {
          "id": "s1",
          "name": "debjyoti-in",
          "profileImageUrl": "https://ppics.in/debjyoti-in-155x155.png",
          "phoneNo": "+91 xxxxxxxxxx"
        },
        "createdAt": 1502110354464,
        "expiresAt": 1502110754464,
        "lastChatAt": "13"
      }
    }
  ]
}
*/

Running examples

• Clone this repository
• Install dev dependencies
• run example/server.js with nodejs

git clone https://github.com/Eyezon/flat2hier-graphql
yarn install # or npm install
node example/server.js