Question

我正在创建一个批量邮件程序，该邮件程序使公司可以将电子邮件模板发送到包含X个订户的特定计划。

但是，当使用pg-promise时，我无法弄清楚如何遍历包含一个或多个唯一计划名称的数组，然后将其用作随后的查询的查询参数以收集单个结果数组。 后续查询在Express发送回指定的错误消息之前无法解决。

例如：

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

返回JSON对象...

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

然后，我想遍历此plans数组以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“唯一计划”，因此我试图找出如何使此查询起作用：

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不在等待pg-promise解决。因此，它触发了我的500台服务器“尚未配置路由”消息，然后< / strong>解决查询：

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' ]

功能如下：

async (req, res, done) => { if (!req.body) { return res.status(404).json({ message: "Missing query parameters" }); done(); } try { const selectedTemplate = await db.oneOrNone("SELECT * FROM templates WHERE userid=$1 and uniqueTemplateName=$2", [req.session.id, uniquetemplatename]); if (!selectedTemplate) { return res.status(404).json({ message: "Unable to locate selected template" }); done(); } console.log('selectedTemplate', selectedTemplate); 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" }) } catch (err) { res.status(500).json({ message: err }); done(); } }

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()，但同样，在Express发送回邮件之前，查询没有解决。

Answer 1

找出问题所在。以防万一其他人迷失了这种困境：“ map”和“ each”之类的功能无法处理异步/等待。相反，他们只是返回一个未决的Promise。因此，您需要使用Bluebird之类的库，该库实现基于Promise的each / map / etc函数（在“集合”下）。

上述解决方法可以起作用：

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); }

pg-promise-无法解决多个查询

1 个答案: