Support or documentation for transaction commit timestamp

[majelbstoat]

Because Spanner doesn't support RETURNING (I wish it did!), when creating a record using Spanner.COMMIT_TIMESTAMP, I want to replace that placeholder with the timestamp of the commit before returning my created object to the client.

In the golang library, the commited timestamp is returned as the result of the transaction:

user := &User{
  CreatedAt: spanner.COMMIT_TIMESTAMP,
}
ts, err := s.db.ReadWriteTransaction(ctx, func(ctx context.Context, txn *spanner.ReadWriteTransaction) error {
  // ... Insert
})
if err != nil {
  return err, nil
}
user.CreatedAt = ts
return nil, user

However, there is currently either no way to do this in the node library, or the documentation does not make it clear how.

If it's not in the library yet, one possible option would be making it the return result of the commit() method.

• @google-cloud/spanner version: 1.5

[callmehiphop]

I believe this is actually possible, but I agree we could be doing a better job of documenting it.

database.runTransaction((err, transaction) => {
  // ... insert/etc.
  transaction.commit((err, response) => {
    const ts = response.commitTimestamp;
  });
});

[majelbstoat]

oh, cool. let me check that out, thanks :)

[majelbstoat]

Can confirm that this works both for callback, and promise-style. Thanks!

(Feel free to close unless you want to keep it open for documentation)