mongodb/mongoid · error · Mongoid::Errors::InvalidQuery

$not arguments must be operators: #

Error message

$not arguments must be operators: #{Errors::InvalidQuery.truncate_expr(k)}

What it means

Raised by Mongoid::Matcher::Not.matches? when a key inside the $not Hash condition does not start with '$'. $not may only contain operator expressions (like $gt, $regex), not plain field comparisons; the faulting input is the non-operator key k.

Solutions

1. Use operator keys inside $not, e.g. { field: { '$not' => { '$eq' => 5 } } }
2. Move plain equality negations to $ne at the field level

When it happens

Trigger: Thrown at lib/mongoid/matcher/not.rb:31 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of mongodb/mongoid@0da0e23d71 (2026-08-23). Data as JSON: /api/errors/ef8515ebd360def6. Report an issue: GitHub.

Appendix: source

Thrown at lib/mongoid/matcher/not.rb:31

      # @param [ Hash | Regexp | BSON::Regexp::Raw ] condition
      #   The $not condition predicate.
      #
      # @return [ true | false ] Whether the value matches.
      #
      # @api private
      module_function def matches?(exists, value, condition)
        case condition
        when ::Regexp, BSON::Regexp::Raw
          !Regex.matches?(exists, value, condition)
        when Hash
          if condition.empty?
            raise Errors::InvalidQuery, "$not argument cannot be an empty hash: #{Errors::InvalidQuery.truncate_expr(condition)}"
          end

          condition.all? do |(k, cond_v)|
            k = k.to_s
            unless k.start_with?('$')
              raise Errors::InvalidQuery, "$not arguments must be operators: #{Errors::InvalidQuery.truncate_expr(k)}"
            end

            !FieldOperator.get(k).matches?(exists, value, cond_v)
          end
        else
          raise Errors::InvalidQuery, "$not argument must be a Hash or a regular expression: #{Errors::InvalidQuery.truncate_expr(condition)}"
        end
      end
    end
  end
end

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