MongoDB函数-引用集合和更新值

Question

我有一个集合‘事务’，有一对多的关系与文件引用的另一个集合‘库存’。我正在尝试编写一个函数，在添加事务时，查找当前的库存数量，以查看是否有足够的资金来完成事务。如果存在，则减去所需的库存(也称为更新集合)来完成事务。

事务收集

db.transaction.find({"_id":"transaction_3"},{"_id":0,"inventory":1})

{ "inventory" : [ { "inventory_id" : "inv_9", "stock" : 488 }, { "inventory_id" : "inv_10", "stock" : 102 }, { "inventory_id" : "inv_11", "stock" : 614 } ] }

存货收集

db.inventory.find({"_id": "inv_9"}, {"stock":1})

{ "_id" : "inv_9", "stock" : 7151844 }

如何循环遍历事务列表，获取库存id和所需库存数量，然后转到库存集合以减去它？

任何帮助都是非常感谢的。

Answer 1

你是在找这样的东西吗？

库存文件：

{"_id":"inv_9","stock":1213574,"desc":"This is widget 9"}
{"_id":"inv_10","stock":25,"desc":"This is Widget 10"}
{"_id":"inv_11","stock":5510381,"desc":"This is widget 11"}

交易文件：

{
    "_id":"transaction_3",
    "desc":"Sample Transaction 3",
    "inventory":[
        {"inventory_id":"inv_9","stock":488},
        {"inventory_id":"inv_10","stock":102},
        {"inventory_id":"inv_11","stock":614},
        {"inventory_id":"not_there","stock":90000000}
        ]
}

处理事务和循环库存数组的代码，以更新每个库存文档。这应该提供足够的信息来根据您的要求创建验证步骤(不确定您是在执行“全部或无”或“任何”类型的更新)。

const MongoClient = require('mongodb').MongoClient;
const url = 'mongodb://localhost:27017';

async function invUpdate() {
    const client = await MongoClient.connect(url, {useNewUrlParser: true})
        .catch(err => {
            console.log(err);
        });
    if (!client) {
        return;
    }
    try {
        const db = client.db("mrp");
        let inv = db.collection('inv');
        let trans = db.collection('trans');
        let query = {};
        const trx = await trans.find(query).forEach(function (item) {
                item.inventory.forEach(async function (order) {
                    let reduceBy = order.stock * -1;
                    const updInv = inv.updateOne({_id: order.inventory_id, stock: {$gte: order.stock}}, 
                        {$inc: {stock: reduceBy}});
                    updInv.then((good) => {
                        if (good.result.nModified === 1) {
                            console.log(`Success, Inventory id ${order.inventory_id} was reduced by ${order.stock} `);
                        } else {
                            console.log(`Unable to update ${order.inventory_id}`);
                        }
                    });
                    updInv.catch((bad) => {
                        console.log('Something did go right ' + bad)
                    })
                });
            }
        );
    } catch
        (err) {
        console.log(err);
    } finally {
        client.close();
    }
}

invUpdate();

产出：

成功后，库存id inv_9减少了488。 无法更新inv_10 成功后，库存id inv_11减少了614。 无法更新not_there