Core API の使用

{ _id: 98765, orders: [] }

{ item: "sunblock", item_id: 5432, qty: 85 },{ item: "beach towel", item_id: 7865, qty: 41 }

const cart = [  { item: 'sunblock', item_id: 5432, qty: 1, price: 5.19 },  { item: 'beach towel', item_id: 7865, qty: 2, price: 15.99 }];const payment = { customer: 98765, total: 37.17 };

async function placeOrder(client, cart, payment) {  const transactionOptions = {    readConcern: { level: 'snapshot' },    writeConcern: { w: 'majority' },    readPreference: 'primary'  };
  // Start the session  const session = client.startSession();  try {    // Start the transaction in the session, specifying the transaction options    session.startTransaction(transactionOptions);
    const ordersCollection = client.db('testdb').collection('orders');    /* Within the session, insert an order that contains information about the    customer, items purchased, and the total payment */    const orderResult = await ordersCollection.insertOne(      {        customer: payment.customer,        items: cart,        total: payment.total,      },      { session }    );
    const inventoryCollection = client.db('testdb').collection('inventory');        for (const item of order) {        /* Update the inventory for the purchased items. End the      transaction if the quantity of an item in the inventory is      insufficient to complete the purchase. */      const inStock = await inventoryCollection.findOneAndUpdate(        {          item_id: item.item_id,          item_id: { $gte: item.qty }        },        { $inc: { 'qty': -item.qty }},        { session }      )      if (inStock === null) {        throw new Error('Insufficient quantity or item ID not found.');      }    }
    const customerCollection = client.db('testdb').collection('customers');
    // Within the session, add the order details to the "orders" array of the customer document    await customerCollection.updateOne(      { _id: payment.customer },      { $push:  { orders: orderResult.insertedId }},      { session }    );
    // Commit the transaction to apply all updates performed within it    await session.commitTransaction();    console.log('Transaction successfully committed.');
  } catch (error) {    /*      Handle any exceptions thrown during the transaction and end the      transaction. Roll back all the updates performed in the transaction.    */    if (error instanceof MongoError && error.hasErrorLabel('UnknownTransactionCommitResult')) {      // Add your logic to retry or handle the error    }    else if (error instanceof MongoError && error.hasErrorLabel('TransientTransactionError')) {      // Add your logic to retry or handle the error    } else {      console.log('An error occured in the transaction, performing a data rollback:' + error);    }    await session.abortTransaction();  } finally {    // End the session    await session.endSession();  }}

{  "_id": 98765,  "orders": [    "61dc..."  ]}

[  {    "_id": ...,    "item": "sunblock",    "item_id": 5432,    "qty": 84  },  {    "_id": ...,    "item": "beach towel",    "item_id": 7865,    "qty": 39  }]

[  {    "_id": "...",    "customer": 98765,    "items": [      {        "item": "sunblock",        "item_id": 5432,        "qty": 1,        "price": 5.19      },      {        "item": "beach towel",        "item_id": 7865,        "qty": 2,        "price": 15.99      }    ],    "total": 37.17  }]