Method: Sequel::SQL::BooleanExpression.invert

Defined in:
lib/sequel/sql.rb

.invert(ce) ⇒ Object

Invert the expression, if possible. If the expression cannot be inverted, raise an error. An inverted expression should match everything that the uninverted expression did not match, and vice-versa, except for possible issues with SQL NULL (i.e. 1 == NULL is NULL and 1 != NULL is also NULL).

BooleanExpression.invert(:a) # NOT "a"


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# File 'lib/sequel/sql.rb', line 1149

def self.invert(ce)
  case ce
  when BooleanExpression
    case op = ce.op
    when :AND, :OR
      BooleanExpression.new(OPERATOR_INVERSIONS[op], *ce.args.map{|a| BooleanExpression.invert(a)})
    when :IN, :"NOT IN"
      BooleanExpression.new(OPERATOR_INVERSIONS[op], *ce.args.dup)
    else
      if ce.args.length == 2
        case ce.args[1]
        when Function, LiteralString, PlaceholderLiteralString
          # Special behavior to not push down inversion in this case because doing so
          # can result in incorrect behavior for ANY/SOME/ALL operators.
          BooleanExpression.new(:NOT, ce)
        else
          BooleanExpression.new(OPERATOR_INVERSIONS[op], *ce.args.dup)
        end
      else
        BooleanExpression.new(OPERATOR_INVERSIONS[op], *ce.args.dup)
      end
    end
  when StringExpression, NumericExpression
    raise(Sequel::Error, "cannot invert #{ce.inspect}")
  when Constant
    CONSTANT_INVERSIONS[ce] || raise(Sequel::Error, "cannot invert #{ce.inspect}")
  else
    BooleanExpression.new(:NOT, ce)
  end
end