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await — co

'use strict';

const mysql = require('mysql2/promise');

async function test() {
  const c = await mysql.createConnection({
    port: 3306,
    user: 'testuser',
    namedPlaceholders: true,
    password: 'testpassword',
  });
  console.log('connected!');
  const [rows, fields] = await c.query('show databases');
  console.log(rows);

  try {
    const [rows, fields] = await c.query('some invalid sql here');
  } catch (e) {
    console.log('caught exception!', e);
  }

  console.log(await c.execute('select sleep(0.5)'));
  console.log('after first sleep');
  console.log(await c.execute('select sleep(0.5)'));
  console.log('after second sleep');
  let start = +new Date();
  console.log(
    await Promise.all([
      c.execute('select sleep(2.5)'),
      c.execute('select sleep(2.5)'),
    ])
  );
  console.log(
    'after 2+3 parallel sleep which is in fact not parallel because commands are queued per connection'
  );
  let end = +new Date();
  console.log(end - start);
  await c.end();

  const p = mysql.createPool({
    port: 3306,
    user: 'testuser',
    namedPlaceholders: true,
    password: 'testpassword',
  });
  console.log(await p.execute('select sleep(0.5)'));
  console.log('after first pool sleep');
  start = +new Date();
  console.log(
    await Promise.all([
      p.execute('select sleep(2.5)'),
      p.execute('select sleep(2.5)'),
    ])
  );
  console.log('after 2+3 parallel pool sleep');
  end = +new Date();
  console.log(end - start);
  await p.end();
}

test()
  .then(() => {
    console.log('done');
  })
  .catch((err) => {
    console.log('error!', err);
    throw err;
  });