Caught DatabaseError while rendering: no such function: IF

[yomguy]

Hi !

MySQL and SQLite3 seem to have different behaviour here : 

when I have {% if collections %} in a template, where collections is a queryset,
using SQlite3 gives this exception :

"Caught DatabaseError while rendering: no such function: IF"...

No pb with MySQL... Any idea please ?

Thanks ;)
Yomguy

[Daniel Roseman]

What is `collections`? How are you getting it? How are you passing it to the template?

--

DR. 

[yomguy]

collections is a queryset coming from urls.py:

all_collections = { 'queryset': MediaCollection.objects.enriched(), }

and passed to the template like this:

url(r'^collections/$', 'django.views.generic.list_detail.object_list',

        dict(all_collections, paginate_by=20, template_name="telemeta/collection_list.html"), name="telemeta-collections"),

In the main template:

{% block content %}

{% with object_list as collections %}

<div class="fullpage">

{% include "telemeta/inc/collection_list.html" %}

</div>

{% endwith %}

{% endblock %}

In the included template:

{% load telemeta_utils %}

{% load i18n %}

{% if collections %}

{% if hits %}

......

[Daniel Roseman]

On Tuesday, 21 June 2011 11:13:35 UTC+1, yomguy wrote:

collections is a queryset coming from urls.py:

all_collections = { 'queryset': MediaCollection.objects.enriched(), }

But what is 'enriched()'? Honestly, if you're using custom code to get objects, and are having trouble in a view that uses that custom code, don't you think you should post the function?

--

DR. 

[Parisson]

Hi !

MySQL and SQLite3 seem to have different behaviour here :

when I have {% if collections %} in a template, where collections is a queryset,
using SQlite3 gives this exception :

"Caught DatabaseError while rendering: no such function: IF"...

No pb with MySQL... Any idea please ?

Thanks ;)

YomGuy

I do LOVE Django :)

[yomguy]

Sorry Daniel, you're right ! 

I thought the exception pointed out the "if" statement in the template, but it is in fact the "IF" command in my MediaCollectionQuerySet.

Here is a part of the MediaCollectionManager with its "enriched" method:

class MediaCollectionManager(CoreManager):

    "Manage collection queries"

    def get_query_set(self):

        "Return the collection query"

        return MediaCollectionQuerySet(self.model)

    def enriched(self):

        "Query set with additional virtual fields such as apparent_collector"

        return self.get_query_set().virtual('apparent_collector')

 

And the MediaCollectionQuerySet with its "virtual" method:

class MediaCollectionQuerySet(CoreQuerySet): 

    def virtual(self, *args):
        qs = self
        for f in args:
            if f == 'apparent_collector':
                qs = qs.extra(select={f: 'IF(media_collections.collector_is_creator, '
                                         'media_collections.creator, media_collections.collector)'})
            else:
                raise Exception("Unsupported virtual field: %s" % f)
        return qs                

See for more details:

http://telemeta.org/browser/telemeta/models/query.py#L327

http://telemeta.org/browser/telemeta/models/query.py#L279

Thanks for your help Daniel and others,

G

[yomguy]

Sorry for the flood !

yomguy

[yomguy]

OK, this "virtual" method calls a MySQL command that need to be translated in SQLite language if I need it.

One solution is to check the engine used in settings.

Y