Postgresql pg promise-不解析多个查询

我正在创建一个群发邮件程序，允许公司向包含X个订户的特定计划发送电子邮件模板

但是，在使用pg PROMITE时，我无法理解如何循环遍历包含一个或多个唯一计划名称的数组，这些名称将用作后续查询的查询参数，以收集单个结果数组。在express发回指定的错误消息之前，无法解析后续查询

例如：

const selectedTemplate = await db.oneOrNone("SELECT * FROM templates WHERE userid=$1 and uniqueTemplateName=$2", [req.session.id, req.body.uniquetemplatename])

返回一个JSON对象

{ ...
  plans : [ 'Unique Plan 1', 'Unique Plan 2', 'Unique Plan 3'...],
  ...
}

然后我想通过这个plans数组来收集一些订户电子邮件。由于selectedTemplate的plans数组可以包含一个或多个唯一的计划，因此我试图找出如何使此查询工作：

let subscriberEmails = [];

await each(selectedTemplate.plans, async plan => {
  const emails = await db.any("SELECT email FROM subscribers WHERE userid=$1 AND planName=$2", [req.session.id, plan])          
  each(emails, ({email}) => subscriberEmails.push(email))           
  console.log('Found emails: ', subscriberEmails);
})

console.log('Selected emails: ', subscriberEmails);
res.status(500).json({ message: "Route not configured yet" })

我遇到的问题是Express没有等待pg承诺的解决。因此，它会触发“我的500服务器路由尚未配置”消息，然后解析查询：

14:48:33 SELECT * FROM templates WHERE userid='12345' and uniqueTemplateName='example-unique-template'

        selectedTemplate: anonymous {
          id: '84efa448-b149-11e8-a7fd-3b9e4e9e5ece',
          key: 9,
          userid: '12345',
          status: 'active',
          fromsender: 'example@helpdesk.com',
          subject: 'Thank you for using our services!',
          templatename: 'Example Unique Template',
          uniquetemplatename: 'example-unique-template',
          message: '<h3>This is a test!</h3>',
          plans: [ 'Unique Plan 1', 'Unique Plan 2' ] 
        }

        Selected emails: []

POST /api/messages/create 500 28 - 34.125 ms

14:48:33 SELECT email FROM subscribers WHERE userid='12345' AND planName='Unique Plan 1'

        Found emails:  [ 
         'betatester19@example.com',
         'betatester20@example.com',
         'betatester21@example.com'
        ]

14:48:34 SELECT email FROM subscribers WHERE userid='12345' AND planName='Unique Plan 2'

        Found emails:  [ 
         'betatester19@example.com',
         'betatester20@example.com',
         'betatester21@example.com',
         'betatester1@example.com',
         'betatester2@example.com',
         'betatester3@example.com',
         'betatester4@example.com',
         'betatester5@example.com',
         'betatester6@example.com',
         'betatester7@example.com',
         'betatester8@example.com',
         'betatester9@example.com',
         'betatester10@example.com',
         'betatester11@example.com',
         'betatester12@example.com',
         'betatester13@example.com',
         'betatester14@example.com',
         'betatester15@example.com',
         'betatester16@example.com',
         'betatester17@example.com',
         'betatester18@example.com' 
        ]

大大简化的数据库结构：

├── Template
│   └── Plans (references an array of unique plan name(s))
|
|── Plan
|   └── PlanName (unique plan name)
|
│── Subscriber
|   └── PlanName (references a single unique plan name)
|   └── Email (unique email)

---

我尝试使用db.task，但在Express发回消息之前，这些查询仍然没有解决。

找到了问题所在。以防万一，其他人会遇到这样的困境：像map和each这样的函数不处理async/await。相反，他们只是返回一个待定的承诺。因此，您需要使用类似的库，它实现集合下基于承诺的each/map/etc函数

上述问题的解决方案：

try {
  await db.task('create-message', async t => {
    const selectedTemplate = await t.oneOrNone(findTemplateByName, [req.session.id, uniquetemplatename])
    if (!selectedTemplate) return sendError(unableToLocate('template'), res, done);
    const { fromsender, subject, message, plans, templatename } = selectedTemplate;

    let subscriberEmails = [];
    await Promise.each(plans, async plan => {
        const emails = await t.any(getAllEmailsByPlan, [req.session.id, plan]);
        each(emails, ({email}) => subscriberEmails.push(email));
    })

    if (isEmpty(subscriberEmails)) return sendError(unableToLocate('subscribers in the selected plan(s)'), res, done);

    const msg = {
        to: subscriberEmails,
        from: fromsender,
        replyTo: fromsender,
        subject: subject,
        html: message
    };

    await mailer.sendMultiple(msg);

    await t.none(createMessageTransaction, [req.session.id, templatename, fromsender, subject, currentDate, plans]);

    await t.none(createNotification, [req.session.id, 'mail_outline', `The following template: ${templatename} has been sent out to the subscibers in the following ${plans.length > 1 ? "plans" : "plan"}: ${plans}.`, date]);

    return res.status(201).send(null);
  })
} catch (err) { return sendError(err, res, done); }  

---

这仍然是一个糟糕的解决方案，请参见。@vitaly-t更新了答案。这是更好的解决方案吗？要将所有查询包装到单个任务中？谢谢。现在看起来好多了；你可以让它变得更简单。你真的不需要等待承诺。每一个，一个简单的for循环也会在那里工作，这意味着你不需要把Bluebird带进它，尽管它通常是一个很好的库来使用；然后在任务上，使其非异步；

try {
  await db.task('create-message', async t => {
    const selectedTemplate = await t.oneOrNone(findTemplateByName, [req.session.id, uniquetemplatename])
    if (!selectedTemplate) return sendError(unableToLocate('template'), res, done);
    const { fromsender, subject, message, plans, templatename } = selectedTemplate;

    let subscriberEmails = [];
    await Promise.each(plans, async plan => {
        const emails = await t.any(getAllEmailsByPlan, [req.session.id, plan]);
        each(emails, ({email}) => subscriberEmails.push(email));
    })

    if (isEmpty(subscriberEmails)) return sendError(unableToLocate('subscribers in the selected plan(s)'), res, done);

    const msg = {
        to: subscriberEmails,
        from: fromsender,
        replyTo: fromsender,
        subject: subject,
        html: message
    };

    await mailer.sendMultiple(msg);

    await t.none(createMessageTransaction, [req.session.id, templatename, fromsender, subject, currentDate, plans]);

    await t.none(createNotification, [req.session.id, 'mail_outline', `The following template: ${templatename} has been sent out to the subscibers in the following ${plans.length > 1 ? "plans" : "plan"}: ${plans}.`, date]);

    return res.status(201).send(null);
  })
} catch (err) { return sendError(err, res, done); }