Redo columnDef.UnmarshalJSON

[dkropachev]

As of now it has very clumsy unmarhsaling, let's make it work without retrying on every known columnType

func (cd *ColumnDef) UnmarshalJSON(data []byte) error {
	dataMap := make(map[string]interface{})
	if err := json.Unmarshal(data, &dataMap); err != nil {
		return err
	}

	t, err := GetSimpleTypeColumn(dataMap)
	if err != nil {
		t, err = GetUDTTypeColumn(dataMap)
		if err != nil {
			t, err = GetTupleTypeColumn(dataMap)
			if err != nil {
				t, err = GetMapTypeColumn(dataMap)
				if err != nil {
					t, err = GetBagTypeColumn(dataMap)
					if err != nil {
						return err
					}
				}
			}
		}
	}
	*cd = ColumnDef{
		Name: t.Name,
		Type: t.Type,
	}
	return nil
}

[illia-li]

Impossible to accurately determine functional purpose of this function and there no it usage. What will be at it inputs (cd, data)? Needs some examples.

[dkropachev]

It is json.UnMarshal hook that is called, if present, to unmarshal data to the receiver type.
Here it is used to read schema file into gemini schema definition.
There is a bug #355 that depicts case when unmarshaling went wrong

[dkropachev]

Implemented at #360