[Xesam] Sorting API to be more flexible

[Mikkel Kamstrup Erlandsen]

2008/6/24 Mikkel Kamstrup Erlandsen <mikkel.kamstrup at gmail.com>:
> 2008/6/13 Mikkel Kamstrup Erlandsen <mikkel.kamstrup at gmail.com>:
>> 2008/6/13 Jos van den Oever <jvdoever at gmail.com>:
>>>
>>> 2008/6/13 Urho Konttori <urho.konttori at nokia.com>:
>>> > We have been evaluating the Xesam for multiple uses at Nokia and one of
>>> > them is media player use. In many cases, where all the songs need to be
>>> > listed, they need to be listed with three sorting criteria: Artist,
>>> > Album, Track#. Xesam provides only two sorting criteria. Now, you might
>>> > argue that the application should do the tertiary sorting, but then if
>>> > we say that, then why two sorting criteria, or one?
>>> >
>>> > I'm quite sure this is not the only use case where tertiary sorting (or
>>> > even more) would be beneficial.
>>> >
>>> > Also, the API looks a bit glued when you have primary and secondary
>>> > sorting as the session properties. Why not instead change it to an array
>>> > of sort criteria? So, as to call it just sort.fields?
>>> >
>>> > It would be very good if this sort of change could still be done to the
>>> > xesam 1.0 spec, either next to the current primary and secondary
>>> > sorting, or better yet, as the only way to set the sort order. It would
>>> > be much cleaner way to do it.
>>> >
>>> > Anyway, I'm looking forward to comments on the subject.
>>>
>>> I agree with your suggestion.
>>> We would also need a way for the server to specify what type of
>>> sorting it supports.
>>> For example a readonly property: sortableFields and a property that
>>> says how many sorting fields can be used.
>>> Some servers may not support sorting at all (grep) or allow only
>>> sorting on one field.
>>>
>>
>> I am also for this, although I think it is quite a big feature compared to
>> our current freeze level.
>>
>> It is a good point you raise Jos. I do however think that it might be
>> acceptable to require the servers to be able to sort the hit data. Otherwise
>> one might have to pull massive amounts of hits over the wire only to get
>> those with the highest atime at the top.
>
> Consider this thread bumped. It is our list of blockers I recently
> posted about. We need a clear decision.
>
> I already made my point above.

There has been some discussion on this on IRC which have led me to
believe that the following solution would be optimal for all:

 * Scrap sort.primary and sort.secondary.

 * Introduce three new session properties:

  - sort.fields a read/write list of fields to sort after, in that
order. Default value ['xesam:relevancyRating']. The server should
truncate this list to to the size specified in vendor.maxSortFields if
too many sort fields are requested

  - vendor.sort.maxfields a readonly uint. Specifies how many fields
in sort.fields will be taken into account, as mentioned, sort.fields
should be truncated at this length. This property must be 1 at
minimum. If this value is 0 any number of fields can be used. Default
value is undefined.

 - vendor.sort.fields a readonly list of strings naming all fields the
server can sort after. If this list is empty all known fields can be
used for sorting. Default value is [].

Please comment. Cheers,
Mikkel