Mention in documentation for running transaction in parallel is not possible

[shivan-eyespace]

It's not possible to run transaction in a Promise.all for example.

We should document this.

[koskimas]

To be clear, it IS possible to run a transaction in a Promise.all:

await Promise.all([
  // Completely fine.
  db.transaction().execute((tr) => {
    // Do stuff.
  }),
  db.transaction().execute((tr) => {
    // Do other stuff.
  }),
  db.selectFrom('person').selectAll().execute()
])

It is NOT possible to run Promise.all in a transction:

db.transaction().execute(async (tr) => {
  // NOT OK!
  await Promise.all([
    tr.selectFrom('person').selectAll().execute(),
    tr.selectFrom('pet').selectAll().execute()
  ])
})

Although, I think we should make it possible. Nothing will run in parallel, since it's a single connection, but we should just make things run sequentially if the user does that. In fact, I thought we did that already 🤔 Something is broken if you can't use Promise.all in a transaction, as in it produces wrong results or throws. It should work. Just not be parallel.

[koskimas]

@shivan-eyespace what happens when you try to run Promise.all in a transaction? How does it fail? How is it "not possible"?

[shivan-eyespace]

@koskimas, I should have been more clear.

I should have said when we run Promise.all, it does not work as expected - we get a waterfall as you mention due to single connection (so all queries are still run just not in parallel as we would expect).

Just as you said:

It should work. Just not be parallel.

I can put something in the docs if you would like, but I'm no expert. Or we can close this.