即使过滤条件不匹配，带有 iregex 的 Django 查询集过滤器也会返回所有对象

Question

I need to query database to get list of users based on case insensitive regex search of emails.

User.objects.filter(email__iregex=f'({"|".join(emails)})')

Here emails is a list containing email ids of users. When emails is an empty list the above returns all users from the database. I am unable to figure out why this is occuring? Ideally when emails is empty list, empty queryset should be returned. Can somebody tell me what is wrong with above code.

Answer 1

This is perfectly normal, since the regex has no begin/start anchor, and thus an empty regex matches everything . You can add anchors ^ (the start anchor) and $ (the end anchor) like:

User.objects.filter(email__iregex=f'({'|'.join(emails)})')

but still the problem is not solved completely. If the email adress contains a dot ( . ) that means "matches any character"), if it contains a question mark ( ? ), it will be interpreted as an optional part. You can escape these with re.escape(…) [python-doc] :

from re import escape as 

escaped_emails = '|'.join( emails)
User.objects.filter(email__iregex=f'({escaped_emails})')