Re: [Tracker] question of tracker sparql query multi langauge order

[Martyn Russell <martyn lanedo com>]

On 22/05/13 16:45, Eugene Seo wrote:
> Dear all,

Hello Eugene,

> I have a question of tracker sparql query order with multi langauges.
> Currently tracker supports Sparql  1.0 and sorts the result in unicode
> order, as I know.

Yes it does.

> Is it possible to sort other language prior to English?

Usually sorting by different languages is done by the locale 
settings/environment. Sorting by language per query isn't currently 
possible because we build collations based on the language being used. 
If you change language, we rebuild those collations in the database.

> In SQLite, specific chacracters can be sorted in front with following
> syntax,
> ORDER BY (CASE WHEN str between '0' and '9' THEN 1 WHEN str between 'a'
> and 'z' THEN 2 ELSE 3 END)

This is pretty cool and I didn't know about this I have to say.

> I wonder there is similar syntax of SPARQL query like CASE WHEN THEN of
> SQLITE.

Well, the SPARQL in Tracker is interpreted, some of it (like ORDER BY) 
is used directly for the SQL used in SQLite. I haven't actually tried 
the example you suggest above, have you? I am curious to know if you 
tested this yet? :)

> If there is any way to sort other langague first than English, please
> share with me.

What's interesting here is, that we use libicu or libunistring for the 
collation/sorting. Whether this works or not depends on a few things:

1. We need to fix our parser to allow the CASE/WHEN/END system. A quick 
test here shows we don't allow that right now.

2. I don't actually know how SQLite would treat such a query on a 
collated column, we would need to figure this part out.

If those two steps work, Tracker should support it.

--

Can I ask how you're using tracker to understand why you need to sort 
for different languages by query?

Thanks,

--
Regards,
Martyn

Founder and CEO of Lanedo GmbH.