func NewCharLength(e sql.Expression) sql.Expression {
	return &Length{expression.UnaryExpression{Child: e}, NumChars}
}
NewCharLength returns a new CHAR_LENGTH function.
package function
import (
	"fmt"
	"unicode/utf8"
	"github.com/src-d/go-mysql-server/sql"
	"github.com/src-d/go-mysql-server/sql/expression"
)
type Length struct {
	expression.UnaryExpression
	CountType CountType
}
type CountType bool
const (
	NumBytes = CountType(false)
	NumChars = CountType(true)
)
func NewLength(e sql.Expression) sql.Expression {
	return &Length{expression.UnaryExpression{Child: e}, NumBytes}
}