func (f *Field) ZeroValue() string {
	if f.Type.Code != TypeColumn {
		panic("attempt to get zero value of non-column field")
	}

	switch f.Type.Name {
	case "string":
		return `""`
	case "int":
		// FIXME: we use -1 since at the moment integer criteria are
		// required to be positive.
		return "-1"
	default:
		panic("unsupported zero value")
	}
}
func (f *Field) ZeroValue() string {
	if f.Type.Code != TypeColumn {
		panic("attempt to get zero value of non-column field")
	}

	switch f.Type.Name {
	case "string":
		return `""`
	case "int":
		// FIXME: we use -1 since at the moment integer criteria are
		// required to be positive.
		return "-1"
	default:
		panic("unsupported zero value")
	}
}
// ZeroValue returns the literal representing the zero value for this field. The type
// code of the field must be TypeColumn.