promise.all mongoose operates database - Stack Overflow

Question

Use Promise.all([p1, p2]) to operate two promise functions. Both functions use mongoose internally to operate the database.

If p1 is rejected and p2 is resolved.

My question is, p2 has actually performed operations on the database. Is that so? Or does promise.all ensure that both p1 and p2 resolve before performing actual database operations?

It feels like it is a mongoose transactional issue.

为情所困 · Answer

Promise.all resolves when all given iterables complete, or rejects when any promises fail.
If any promises are passed that rejects , all Promise values immediately fail, discarding all other promises if they are unresolved. If passed any empty array, this method will complete immediately.

var p0 = new Promise((resolve, reject) => {
      setTimeout(() => {
          console.log(1)
      }, 100);
}); 
var p1 = Promise.resolve(3);
var p2 = 1337;
var p3 = new Promise((resolve, reject) => {
  setTimeout(reject, 100, "foo");
}); 
var p4 = new Promise((resolve, reject) => {
      setTimeout(() => {
          console.log(2)
      }, 100);
});
var p = Promise.all([p0, p1, p2, p3, p4]).then(values => { 
  console.log(values);
}, values => {
    console.log(values) // foo
}); // 1 2