race condition in wp_insert_user()

[hanelyp]

Possibility exists for a user record insert between check if a user name already exists and actual database insert. A unique index on wp_users.user_login would prevent this, and allow the code to operate without a separate database query to check for an existing user.

[chriscct7]

Related (and possible solution): #33376

[iandunn]

#54071 was marked as a duplicate.

[iandunn]

#54071 was marked as a duplicate.

[iandunn]

It sounds like adding a `UNIQUE` constraint may not be possible for Core.

r36654 added an index, which should mitigate race conditions to some degree. Not entirely, though, since there's a newer report in #54071.

[simonbuerger]

@iandunn that UNIQUE constraint being discussed is on user_email though, which I understand would break existing installs relying on non-unique emails - but I assume they still have unique user logins. So can there not be a constraint just on user_login?