使用Promise all并行执行函数

Question

我需要执行几个并行函数

第一个函数：数据库获取操作，即从数据库中查找库存详细信息

第二个函数：处理数据库结果并将结果保存为文件

我使用了两个promise，背靠背地执行上面的函数，我觉得这不是正确的方法。有没有处理这些函数调用的更好方法。我得到的结果如下代码，但想知道任何其他方式。

按以下方式执行：

let allQuery = {
sql: "SELECT * from inventory",
};
let inventoryQuery = {
sql: "SELECT * from inventory where inventory='1'",
};
let nearbyQuery = {
sql: "SELECT * from inventory where inventory='2",
};
let firstPromises = [dbService.fetch(allQuery),
dbService.fetch(inventoryQuery),
dbService.fetch(nearbyQuery)
];
Promise.all(firstPromises)
.then((values) => {
let all = values[0];
let inventory = values[1];
let nearby = values[2];
let fileKey1 = folderName + '/' + all.QueryExecutionId + '.csv';
let fileName1 = all.QueryExecutionId + '.csv';
let fileKey2 = folderName + '/' + inventory.QueryExecutionId + '.csv';
let fileName2 = inventory.QueryExecutionId + '.csv';
let fileKey3 = folderName + '/' + nearby.QueryExecutionId + '.csv';
let fileName3 = nearby.QueryExecutionId + '.csv';
let secondPromises = [s3Service.s3StreamDownload(bucketName, fileKey1, fileName1),
s3Service.s3StreamDownload(bucketName, fileKey2, fileName2),
s3Service.s3StreamDownload(bucketName, fileKey3, fileName3)
];
Promise.all(secondPromises)
.then((values) => {
console.log('Do later operation');
}).catch((error) => {
debug(`Error in promises ${error}`);
});
}).catch((error) => {
debug(`Error in promises ${error}`);
});

Answer 1

我认为提取内部函数，然后将它们链接在一起会更可读：

Promise.all(firstPromises)
.then(transformToSecondPromises)
.then(Promise.all)
.then(values => {/* do later operation */})
.catch(error => { debug(`Error in promises ${error}`) })
function transformToSecondPromises ([all, inventory, nearby]) {
const fileKey1 = folderName + '/' + all.QueryExecutionId + '.csv';
const fileName1 = all.QueryExecutionId + '.csv';
const fileKey2 = folderName + '/' + inventory.QueryExecutionId + '.csv';
const fileName2 = inventory.QueryExecutionId + '.csv';
const fileKey3 = folderName + '/' + nearby.QueryExecutionId + '.csv';
const fileName3 = nearby.QueryExecutionId + '.csv';
return [
s3Service.s3StreamDownload(bucketName, fileKey1, fileName1),
s3Service.s3StreamDownload(bucketName, fileKey2, fileName2),
s3Service.s3StreamDownload(bucketName, fileKey3, fileName3)
];
}