Re: Some questions about file handling + some other things

On Wed, Mar 24, 2021 at 11:05:19AM -0400, John P. Rouillard wrote:
> >> context.files.sorted('filetype'), when the 'files' list had an item
> >> with 'filetype' unset.
> >
> >Sorting by Multilink happens in Python not in SQL. What is your use-case
> >for sorting by Multilink? In my experience the sort order created by
> >this is hardly understandable by humans.
> 
> I don't think this is sorting by multilink but sorting the items in a
> multilink. At least thats how I read cgi/templating.py:
> MultilinkHTMLProperty::sorted().

Yep, if this is the only use in current templates this is fine.

> >I would like to deprecate its use.

Note that you *can* sort by Multilinks, there is currently even a
regression test for this.

> IIRC there was either a bug report or email thread about sorting by
> multilinks (as opposed to sorting the elements of a multilink). The
> original design doc calls for sorting by len(multilink) IIRC. I don't
> know what sorting by the multilink prop does currently.

OK, currently its implemented as follows:
- Sort each individual multilink property by its order property
- sort the resulting list of lists

Hardly understandable by humans because if certain lists miss certain
items, the sort order will be completely different.

> I'll have to see if I cand dredge it up. IIRC we came up with a use
> case for this which was saner than the current sorting method.

that would be fine.

> >I also at one time wanted to implement key properties with multiple
> >values: An application often demands uniqueness over several properties
> >not just one. I discussed this *many* years ago with Richard but he
> >feared at the time that things would be complicated by this. I still
> >think it would be a useful feature.
> 
> I would tend to agree it's useful. Maybe a key() function that is
> passed the item? Could be materialized in a _key hidden/reserved
> property name similar to creator/activity....

We already have setkey. This could be enhanced to optionally take a
list. Similar for labelprop and orderprop (which default to the key
property if there is one). The *do* have separate set methods where you
can set a labelprop and/or orderprop, these could be enhanced in a
similar fashion.

Note that once a labelprop can take multiple properties it is unclear
how this should be displayed.

> >> Second try: I do two database query for tasks (the first
> >> one filters on 'deadline is set', and an other one filters on 'deadline
> >> is not set', and join these list.
> >
> >Yes, this can be done in an explicit index template if you really need
> >that behavior.
> 
> Do you have an example? I envision some sort of concatenation of id's
> that result from a search that are sent into request/batch somehow.

Ouch: I didn't think about batches. So far I've used only special pages
without batches. And I don't think you can force a different ordering by
giving IDs or something. So it may well be that this is currently not
possible with batches.

Ralf
-- 
Dr. Ralf Schlatterbeck                  Tel:   +43/2243/26465-16
Open Source Consulting                  www:   www.runtux.com
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