@objectwow/join

Join objects with functionality similar to MongoDB’s $lookup

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Use case

• In a microservices system where each service owns its own database, querying data requires calling multiple services to retrieve the necessary information and manually joining the data. This package simplifies the process of joining data.

• Imagine you have an array of orders. Each order contains fulfillments, and each fulfillment has a list of products. However, in the product data, you’re only storing the productId and quantity. The task is to enrich this data by retrieving the full product details for each product.

Installation

npm i @objectwow/join

Usage

import { joinData } from "@objectwow/join";

const orders = [
  {
    id: 1,
    code: "1",
    fulfillments: [
      {
        id: 11,
        code: "11",
        products: [
          { id: 111, quantity: 1 },
          { id: 112, quantity: 4 },
        ],
      },
      {
        id: 12,
        code: "12",
        products: [{ id: 111, quantity: 8 }],
      },
    ],
  },
];

const products = [
  { id: 111, name: "Product 1", price: 10 },
  { id: 112, name: "Product 2", price: 20 },
  { id: 113, name: "Product 3", price: 30 },
];

const result = await joinData({
  local: orders,
  from: products,
  localField: "fulfillments.products.id",
  fromField: "id",
  as: "fulfillments.products",
  asMap: { name: "name", price: "price" },
});

LocalData (orders) will be overwritten. Order products will have the name and price fields.

orders = [
  {
    id: 1,
    code: "1",
    fulfillments: [
      {
        id: 11,
        code: "11",
        products: [
          { id: 111, name: "Product 1", price: 10, quantity: 1 },
          { id: 112, name: "Product 2", price: 20, quantity: 4 },
        ],
      },
      {
        id: 12,
        code: "12",
        products: [{ id: 111, name: "Product 1", price: 10, quantity: 8 }],
      },
    ],
  },
];

result = {
  allSuccess: true,
  joinFailedValues: [],
};

Note: see more samples in the tests and test-by-cases

/**
 * Parameters for the `joinData` function to perform joins between local data and source data.
 */
export interface JoinDataParam {
  /**
   * Local object or array of local objects to be joined.
   */
  local: LocalParam;

  /**
   * Objects or an asynchronous callback function that returns the data from the source.
   */
  from: FromParam;

  /**
   * Field name in the local object(s) used for the join.
   */
  localField: string;

  /**
   * Field name in the `from` object(s) used for the join.
   */
  fromField: string;

  /**
   * Optional new field name to store the result of the join in the local object(s).
   */
  as?: string;

  /**
   * Optional mapping from the `fromField` values to new field names in the local object(s).
   */
  asMap?: AsMap;
}

export type LocalParam = object | object[];

export type FromParam =
  | ((localFieldValues: Primitive[], metadata: any) => object[])
  | object[];

export type AsMap =
  | ((currentFrom: any, currentLocal: any, metadata: any) => any)
  | { [key: string]: string }
  | string;

Join performance

The join method in @objectwow/join offers better performance compared to the join techniques used by databases, Krakend, Hasura, and GraphQL. Here’s why:

Traditional Approach (Database, Krakend, Hasura, GraphQL):

1. Loop through the original array.
2. For each element, make a call to the database/internal/external service containing the related data by its UID (unique identifier).
3. Combine the data from both sources.
4. This results in a time complexity of O(n x m), where n is the number of elements in the original array, and m is the number of elements fetched from the related table or service.

@objectwow/join Approach:

1. Provides a callback function where the input is UIDs, allowing the developer to fetch related data from the database/internal/external service in a single call.
2. Uses JavaScript’s new Map to optimize the process, reducing the time complexity from O(m) to O(1), where m is the number of elements retrieved..
3. Combines the data efficiently after retrieving it in bulk through a single call.
4. This results in a time complexity of O(n), where n is the number of elements in the original array.

By fetching related data in bulk and leveraging efficient JavaScript data structures, @objectwow/join minimizes redundant calls and improves overall performance.

Tradeoff

Of course, the tools/platforms mentioned above offer capabilities that @objectwow/join cannot provide, such as direct connection to the data source, pagination, conditional filtering, and more.

Test

npm run test or npm run test:cov

File	% Stmts	% Branch	% Funcs	% Lines	Uncovered Line #s
All files	93	78.68	95.23	92.8
core.ts	90.82	73.17	100	90.82	18,42,53,106,128,141,163,206,247,251
singleton.ts	100	100	75	100
util.ts	100	89.47	100	100	23-24

Customization

With an out-of-the-box design, you can create your own function using the current structure.

Customized definition

import { JoinData } from "@objectwow/join";

export class YourJoin extends JoinData {
  // Use case: Currently, deep values are split by a dot ('.'), but you can use a different symbol if needed
  protected separateSymbol: string;

  // Use case: Return your custom output
  protected generateResult(
    joinFailedValues: Primitive[],
    localOverwrite: LocalParam,
    metadata?: any
  ) {}

  // Use case:  Deep clone local data if you want to avoid overwriting the original.
  protected standardizeLocalParam(
    local: LocalParam,
    metadata?: any
  ): Promise<LocalParam> {}

  // Use case: Automatically call internal or external services to retrieve data based on the input
  protected standardizeFromParam(
    from: FromParam,
    localFieldValues: string[],
    metadata?: any
  ): Promise<any[]> {}

  // Use case: Throw an error if the field is invalid
  protected validateFields(
    arr: { key: string; value: any }[],
    metadata?: any
  ): void {}
}

Customized usage

Using solution 1: Override the default JoinData instance

SingletonJoinData.setInstance(new YourJoin())

await joinData({...})

Using solution 2: Create new singleton instances as needed

import { SingletonJoinData } from "@objectwow/join";

export class YourSingletonJoinData extends SingletonJoinData{}

YourSingletonJoinData.setInstance(new YourJoin())

export async function yourJoinDataFunction(
  params: JoinDataParam,
  metadata?: any
): Promise<JoinDataResult> {
  return YourSingletonJoinData.getInstance().execute(params, metadata);
}

await yourJoinDataFunction({...})

Using solution 3: You can directly use your new class without a singleton instance.

const joinCls = new YourJoin()
await joinCls.execute({...})

Tips:

• You can call original function (parent function) with `super.
• You can pass anything to the metadata

Benchmark

• Source:

// Generate localData with 100 orders and 2 fulfillments per order
const localData = Array.from({ length: 100 }, (_, i) => ({
  id: i + 1, // Order ID starting from 1
  code: `${i + 1}`, // Order code
  fulfillments: Array.from({ length: 2 }, (_, j) => ({
    id: (i + 1) * 10 + j, // Fulfillment ID for each order
    code: `${(i + 1) * 10 + j}`, // Fulfillment code
    products: Array.from({ length: 2 }, () => {
      const productId = Math.floor(Math.random() * 100) + 111; // Random product ID between 111 and 210
      return {
        id: productId,
        quantity: Math.floor(Math.random() * 10) + 1, // Random quantity between 1 and 10
      };
    }),
  })),
}));

// Generate fromData with 100 products
const fromData = Array.from({ length: 100 }, (_, i) => ({
  id: i + 111, // IDs starting from 111
  name: `Product ${i + 1}`,
  price: Math.floor(Math.random() * 100 + 1), // Random price between 1 and 100
}));

• Execute: node lib/benchmark.js (need build first)
• Report: JoinData Execution x 125,972 ops/sec ±1.27% (66 runs sampled)
• Device: Macbook Pro M1 Pro, 16 GB RAM, 12 CPU

Questions

1: Why is the original local object overwritten by default?

Because we don’t want memory leaks when cloning large objects. With the overwrite behavior, object references will be reusable, and memory will be used efficiently. Only small temporary data is created at each step and released when it’s no longer needed

If you prefer not to use this behavior, you can:

Solution 1: Deep clone your local object

• const cloneLocal = JSON.parse(JSON.stringify(localObject))
• Use cloneLocal at joinData local parameter

Solution 2: Customize the behavior, as mentioned in the #Customize:

• Overwrite standardizeLocalParam to return JSON.parse(JSON.stringify(local))
• Overwrite generateResult to return localOverwrite
• Follow the next steps in the Customized usage

Contact

If you have any questions, feel free to open an open an issue on GitHub or connect with me on Linkedin.

Thank you for using and supporting the project!

Contributors