rules:
  - id: use-count-method
    message:
      Looks like you need to determine the number of records. Django provides the count() method which is more efficient
      than .len(). See https://docs.djangoproject.com/en/3.0/ref/models/querysets/
    languages: [python]
    severity: ERROR
    pattern-either:
      - pattern: $X.objects.$FUNC(...).len()
      - pattern: $X.objects.$FUNC(...).$FILTER().len()
      - pattern: $X.objects.$FUNC(...).$FILTER().$UPDATE(...).len()
    metadata:
      category: performance
      technology:
        - django