如何从PostgreSQL中提取数据，处理，然后存储在javascript中？

Question

我不太熟悉高级javascript，并寻求一些指导。我希望使用木偶技师-集群将网页内容存储到DB中，下面是一个示例：

const { Cluster } = require('puppeteer-cluster');

(async () => {
  const cluster = await Cluster.launch({
    concurrency: Cluster.CONCURRENCY_CONTEXT,
    maxConcurrency: 2,
  });

  await cluster.task(async ({ page, data: url }) => {
    await page.goto(url);
    const screen = await page.content();
    // Store content, do something else
  });

  cluster.queue('http://www.google.com/');
  cluster.queue('http://www.wikipedia.org/');
  // many more pages

  await cluster.idle();
  await cluster.close();
})();

看起来，我可能不得不使用pg副词连接到db。对此，建议采取什么方法？

这是我的桌子：

+----+-----------------------------------------------------+---------+
| id | url                                                 | content |
+----+-----------------------------------------------------+---------+
| 1  | https://www.npmjs.com/package/pg                    |         |
+----+-----------------------------------------------------+---------+
| 2  | https://github.com/thomasdondorf/puppeteer-cluster/ |         |
+----+-----------------------------------------------------+---------+

我相信我必须将数据拉到数组中(id & url)，每次接收到内容后，将其存储到DB中(by id & content)。

Answer 1

您应该在任务函数之外创建数据库连接：

const { Client } = require('pg');
const client = new Client(/* ... */);
await client.connect();

然后查询数据并将其排队(使用ID，以便以后能够将其保存在数据库中)：

const rows = await pool.query('SELECT id, url FROM your_table WHERE ...');
rows.forEach(row => cluster.queue({ id: row.id, url: row.url }));

然后，在任务函数的末尾，更新表行。

await cluster.task(async ({ page, data: { id, url, id } }) => {
    // ... run puppeteer and save results in content variable
    await pool.query('UPDATE your_table SET content=$1 WHERE id=$2', [content, id]);
});

总之，您的代码应该如下所示(请注意，我没有亲自测试代码)：

const { Cluster } = require('puppeteer-cluster');
const { Client } = require('pg');

(async () => {
    const client = new Client(/* ... */);
    await client.connect();

    const cluster = await Cluster.launch({
        concurrency: Cluster.CONCURRENCY_CONTEXT,
        maxConcurrency: 2,
    });

    await cluster.task(async ({ page, data: { id, url } }) => {
        await page.goto(url);
        const content = await page.content();
        await pool.query('UPDATE your_table SET content=$1 WHERE id=$2', [content, id]);
    });

    const rows = await pool.query('SELECT id, url FROM your_table');
    rows.forEach(row => cluster.queue({ id: row.id, url: row.url }));

    await cluster.idle();
    await cluster.close();
})();