Create a Smart relationship

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Create a Smart relationship

What is a Smart Relationship?

Sometimes, you want to create a virtual relationship between two set of data that does not exist in your database. A concrete example could be creating a relationship between two collections available in two different databases. Creating a Smart Relationship allows you to customize with code how your collections are linked together.

Create a BelongsTo Smart Relationship

On the Live Demo example, we have an order which belongsTo a customer which belongsTo a delivery address. We’ve created here a BelongsTo Smart Relationship that acts like a shortcut between the order and the delivery address.

A BelongsTo Smart Relationship is created like a Smart Field with the reference option to indicate on which collection the Smart Relationship points to. You will also need to code the logic of the search query.

/forest/orders.js

const { collection } = require('forest-express-sequelize');
const models = require('../models');

collection('orders', {
  fields: [{
    field: 'delivery_address',
    type: 'String',
    reference: 'addresses.id',
    get: function (order) {
      return models.addresses
        .findAll({
          include: [{
            model: models.customers,
            where: { id: order.customer_id },
            include: [{
              model: models.orders,
              where: { ref: order.ref }
            }]
          }],
        })
        .then((addresses) => {
          if (addresses) { return addresses[0]; }
        });
    }
  }]
});

/forest/orders.js

const { collection } = require('forest-express-mongoose');
const Address = require('../models/addresses');

collection('Order', {
  fields: [
    {
      field: 'delivery_address',
      type: 'String',
      reference: 'Address._id',
      get: function (order) {
        return Address.aggregate([
          {
            $lookup: {
              from: 'orders',
              localField: 'customer_id',
              foreignField: 'customer_id',
              as: 'orders_docs',
            },
          },
          {
            $match: {
              'orders_docs._id': order._id,
            },
          },
        ]).then((addresses) => {
          if (addresses) {
            return addresses[0]._id;
          }
        });
      },
    },
  ],
});

lib/forest_liana/collections/order.rb

class Forest::Order
  include ForestLiana::Collection

  collection :Order

  search_delivery_address = lambda do |query, search|

    query.joins(customer: :address).or(Order.joins(customer: :address).where("addresses.country ILIKE ?", "%#{search}%"))

  end

  belongs_to :delivery_address, reference: 'Address.id', search: search_delivery_address do
    object.customer.address
  end
end

app/forest/order.py

from django_forest.utils.collection import Collection
from app.models import Order, Address


class OrderForest(Collection):
    def load(self):
        self.fields = [
            {
                'field': 'delivery_address',
                'reference': 'app_addresses.id',
                'type': 'String',
                'get': self.get_delivery_address,
            }
        ]

    def get_delivery_address(self, obj):
        queryset = Address.objects.filter(customer=obj.customer)
        if len(queryset):
            return queryset[0]

Collection.register(OrderForest, Order)

Ensure the file app/forest/__init__.py exists and contains the import of the previous defined class :

app/forest/__init__.py

from app.forest.orders import OrderForest

app/Models/Order.php

<?php

namespace App\Models;

use ForestAdmin\LaravelForestAdmin\Services\Concerns\ForestCollection;
use ForestAdmin\LaravelForestAdmin\Services\SmartFeatures\SmartRelationship;
use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;

/**
 * Class Order
 */
class Order extends Model
{
    use HasFactory, ForestCollection;

    /**
     * @return SmartRelationship
     */
    public function deliveryAddress(): SmartRelationship
    {
        return $this->smartRelationship(
            [
                'type' => 'String',
                'reference' => 'address.id'
            ]
        )
            ->get(
                function () {
                    return Order::join('customers', 'customers.id', '=', 'orders.customer_id')
                        ->join('addresses', 'addresses.customer_id', '=', 'customers.id')
                        ->where('orders.id', $this->id)
                        ->first();
                }
            );
    }
}

Create a HasMany Smart Relationship

On the Live Demo example, we have a product hasMany orders and an order belongsTo customer. We’ve created a Smart Relationship that acts like a shortcut: product hasMany customers.

A HasMany Smart Relationship is created like a Smart Field with the reference option to indicates on which collection the Smart Relationship points to.

/forest/products.js

const { collection } = require('forest-express-sequelize');

collection('products', {
  fields: [
    {
      field: 'buyers',
      type: ['String'],
      reference: 'customers.id',
    },
  ],
});

/forest/products.js

const { collection } = require('forest-express-mongoose');

collection('products', {
  fields: [
    {
      field: 'buyers',
      type: ['String'],
      reference: 'Customer._id',
    },
  ],
});

lib/forest_liana/collections/product.rb

class Forest::Product
  include ForestLiana::Collection

  collection :Product

  has_many :buyers, type: ['String'], reference: 'Customer.id'
end

app/forest/product.py

from django_forest.utils.collection import Collection
from app.models import Product


class ProductForest(Collection):
    def load(self):
        self.fields = [
            {
                'field': 'buyers',
                'reference': 'app_customer.id',
                'type': ['String'],
            }
        ]


Collection.register(ProductForest, Product)

app/Models/Product.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;


/**
 * Class Product
 */
class Product extends Model
{
    use HasFactory;

    /**
     * @return SmartRelationship
     */
    public function buyers(): SmartRelationship
    {
        return $this->smartRelationship(
            [
                'type' => ['String'],
                'reference' => 'customer.id'
            ]
        );
    }
}

Upon browsing, an API call is triggered when accessing the data of the HasMany relationships in order to fetch them asynchronously. In the following example, the API call is a GET on /products/:product_id/relationships/buyers.

Option 1: using Sequelize ORM

We’ll use the findAll and count methods provided by Sequelize to find and count all customers who bought the current product (buyers).

Then, you should handle pagination in order to avoid performance issue. The API call has a query string available which gives you all the necessary parameters you need to enable pagination.

Finally, you don’t have to serialize the data yourself. The Forest Admin agent already knows how to serialize your collection (customers in this example). You can access to the serializer through the recordsGetter.serialize function.

/routes/products.js

const express = require('express');
const {
  PermissionMiddlewareCreator,
  RecordSerializer,
} = require('forest-express-sequelize');
const { products, customers, orders } = require('../models');

const router = express.Router();
const permissionMiddlewareCreator = new PermissionMiddlewareCreator('products');

router.get(
  '/products/:product_id/relationships/buyers',
  (request, response, next) => {
    const productId = request.params.product_id;
    const limit = parseInt(request.query.page.size, 10) || 20;
    const offset = (parseInt(request.query.page.number, 10) - 1) * limit;
    const include = [
      {
        model: orders,
        as: 'orders',
        where: { product_id: productId },
      },
    ];

    // find the customers for the requested page and page size
    const findAll = customers.findAll({
      include,
      offset,
      limit,
    });

    // count all customers for pagination
    const count = customers.count({ include });

    // resolve the two promises and serialize the response
    const serializer = new RecordSerializer(customers);
    Promise.all([findAll, count])
      .then(([customersFound, customersCount]) =>
        serializer.serialize(customersFound, { count: customersCount })
      )
      .then((recordsSerialized) => response.send(recordsSerialized))
      .catch(next);
  }
);

Option2: using raw SQL

We’ll use raw SQL query and Sequelize to count and find all customers who bought the current product (buyers).

Then, you should handle pagination in order to avoid performance issue. The API call has a query string available which gives you all the necessary parameters you need to enable pagination.

/routes/products.js

const express = require('express');
const router = express.Router();
const models = require('../models');

router.get('/products/:product_id/relationships/buyers', (req, res, next) => {
  let limit = parseInt(req.query.page.size) || 10;
  let offset = (parseInt(req.query.page.number) - 1) * limit;
  let queryType = models.sequelize.QueryTypes.SELECT;

  let countQuery = `
    SELECT COUNT(*)
    FROM customers
    JOIN orders ON orders.customer_id = customers.id
    JOIN products ON orders.product_id = products.id
    WHERE product_id = ${req.params.product_id};
  `;

  let dataQuery = `
    SELECT customers.*
    FROM customers
    JOIN orders ON orders.customer_id = customers.id
    JOIN products ON orders.product_id = products.id
    WHERE product_id = ${req.params.product_id}
    LIMIT ${limit}
    OFFSET ${offset}
  `;

  const serializer = new RecordSerializer(customers);
  Promise.all([
    // Since support to multiple db connections was added you have to use the connection name defined in config/databases.js
    // here using default
    models.connections.default.query(countQuery, { type: queryType }),
    models.connections.default.query(dataQuery, { type: queryType }),
  ])
    .then(([count, queryResult]) =>
      serializer.serialize(queryResult[0], { count: count[0].count })
    )
    .then((serializedResult) => res.send(serializedResult))
    .catch((err) => next(err));
});

module.exports = router;

If your primary key column name (customer_id) is different than the model field name (customerId), you must alias the primary key column with the name of the model field in the dataQuery. Ex: SELECT customers.*, customers.customer_id AS “customerId”

We use the $lookup operator of the aggregate pipeline. Since there's a many-to-many relationship between Product and Customer, the $lookup operator needs to look into orders which is an array we have to flatten first using $unwind.

Finally, you don’t have to serialize the data yourself. The Forest Admin agent already knows how to serialize your collection (Customer in this example). You can access to the serializer through the Liana.ResourceSerializer object.

/forest/products.js

const { collection } = require('forest-express-mongoose');

collection('products', {
  fields: [
    {
      field: 'buyers',
      type: ['String'],
      reference: 'Customer._id',
    },
  ],
});

/routes/products.js

const P = require('bluebird');
const express = require('express');
const router = express.Router();
const Liana = require('forest-express-mongoose');
const { Customers } = require('../models');
const mongoose = require('mongoose');

router.get('/Product/:product_id/relationships/buyers', (req, res, next) => {
  let limit = parseInt(req.query.page.size) || 10;
  let offset = (parseInt(req.query.page.number) - 1) * limit;

  let countQuery = Customers.aggregate([
    {
      $lookup: {
        from: 'orders',
        localField: 'orders',
        foreignField: '_id',
        as: 'orders_docs',
      },
    },
    {
      $unwind: '$orders_docs',
    },
    {
      $lookup: {
        from: 'products',
        localField: 'orders_docs._id',
        foreignField: 'orders',
        as: 'products_docs',
      },
    },
    {
      $match: {
        'products_docs._id': mongoose.Types.ObjectId(req.params.product_id),
      },
    },
    {
      $count: 'products_docs',
    },
  ]);

  let dataQuery = Customers.aggregate([
    {
      $lookup: {
        from: 'orders',
        localField: 'orders',
        foreignField: '_id',
        as: 'orders_docs',
      },
    },
    {
      $unwind: '$orders_docs',
    },
    {
      $lookup: {
        from: 'products',
        localField: 'orders_docs._id',
        foreignField: 'orders',
        as: 'products_docs',
      },
    },
    {
      $match: {
        'products_docs._id': mongoose.Types.ObjectId(req.params.product_id),
      },
    },
  ]);

  return P.all([countQuery, dataQuery])
    .spread((count, customers) => {
      const serializer = new Liana.RecordSerializer(Customers);
      return serializer.serialize(customers, { count: count.orders_count });
    })
    .then((products) => {
      res.send(products);
    })
    .catch((err) => next(err));
});

module.exports = router;

We’ve built the right SQL query using Active Record to count and find all customers who bought the current product.

Then, you should handle pagination in order to avoid performance issue. The API call has a querystring available which gives you all the necessary parameters you need to enable pagination.

Rails.application.routes.draw do
  # MUST be declared before the mount ForestLiana::Engine.
  namespace :forest do
    get '/Product/:product_id/buyers' => 'orders#buyers'
  end

  mount ForestLiana::Engine => '/forest'
end

class Forest::ProductsController < ForestLiana::ApplicationController
  def buyers
    limit = params['page']['size'].to_i
    offset = (params['page']['number'].to_i - 1) * limit

    product = Product.find(params['product_id'])
    customers = Customer.where(order_id: product.orders.ids)

    render json: serialize_models(customers.limit(limit).offset(offset), meta: {count: customers.count})
  end
end

app/urls.py

from django.urls import path
from django.views.decorators.csrf import csrf_exempt

from . import views

app_name = 'app'
urlpatterns = [
    path('/app_product/<pk>/relationships/buyers', views.BuyersView.as_view(), name='product-buyers'),
]

Then create the pertained view

app/views.py

from django.http import JsonResponse
from django.views import generic

from django_forest.resources.utils.queryset import PaginationMixin
from django_forest.utils.schema.json_api_schema import JsonApiSchema

class BuyersView(PaginationMixin, generic.ListView):

    def get(self, request, pk, *args, **kwargs):
        params = request.GET.dict()

        # queryset
        queryset = Customer.objects.filter(order__product_id=pk).distinct()

        # pagination
        queryset = self.get_pagination(params, queryset)

        # json api serializer
        Schema = JsonApiSchema.get('app_customer')
        data = Schema().dump(queryset, many=True)

        return JsonResponse(data, safe=False)

We’ve built the right SQL query using Django ORM to find all customers who bought the current product.

Then, you should handle pagination in order to avoid performance issue. The API call has a querystring available which gives you all the necessary parameters you need to enable pagination.

Finally, you don’t have to serialize the data yourself. The Forest Admin agent already knows how to serialize your collection (Customer in this example, with the table name app_customer). You can access to the serializer through the Schema().dump function (using marshmallow-jsonapi internally).

We’ve built the right SQL query using Active Record to count and find all customers who bought the current product.

Then, you should handle pagination in order to avoid performance issue. The API call has a querystring available which gives you all the necessary parameters you need to enable pagination.

routes/web.php

<?php

use App\Http\Controllers\ProductsController;
use Illuminate\Support\Facades\Route;


Route::get('forest/product/{id}/relationships/buyers', [ProductsController::class, 'buyers']);

app/Http/controllers/ProductsController.php

<?php

namespace App\Http\Controllers;

use App\Models\Customer;
use ForestAdmin\LaravelForestAdmin\Facades\JsonApi;
use ForestAdmin\LaravelForestAdmin\Http\Controllers\ForestController;
use Illuminate\Http\JsonResponse;

/**
 * Class ProductsController
 */
class ProductsController extends ForestController
{
    /**
     * @param int $id
     * @return JsonResponse
     */
    public function buyers(int $id): JsonResponse
    {
        $query = Customer::whereHas('orders.products', fn ($query) => $query->where('products.id', $id))
            ->paginate($pageParams['size'] ?? null, '*', 'page', $pageParams['number'] ?? null);

        return response()->json(
            JsonApi::render($query, 'customers', ['count' => $query->total()])
        );
    }
}

PreviousRelationships NextGetIdsFromRequest

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