code: func ruleConstantFalse(ctx sessionctx.Context, i, j int, exprs *exprSet) {
  	cond := exprs.data[i]
  	if cons, ok := cond.(*Constant); ok {
  		v, isNull, err := cons.EvalInt(ctx, chunk.Row{})
  		if err != nil {
  			logutil.Logger(context.Background()).Warn("eval constant", zap.Error(err))
  			return
  		}
  		if !isNull && v == 0 {
  			exprs.SetConstFalse()
  		}
  	}
  }
docs: // ruleConstantFalse propagates from CNF condition that false plus anything returns false.
  // false, a = 1, b = c ... => false