That's a good idea..
Its a bit exhausting discussing stuff like this on a
mailing list ...
Well - if you ever plan to held one you can count on me if it's in one
of the famous french ski ressorts.
Earlier this year I'd been to Portes du soleil -Avoriaz - Morzine ..
e.t.c - you can count on me during the season ;)
Now I'm not sure that ski
resorts that are 6 hours away from Paris in
train would be best (though I skied in Avoriaz too :)) if we want to get
non french people out there.
It's worth discussing who would join.
Ludovic
Am 05.04.2011 19:40, schrieb Vincent Massol:
Hi Andreas,
On Apr 5, 2011, at 7:17 PM, Andreas Hahn wrote:
Again this is sort of scaring discussion to me.
For minimal benefits - and there is still no persuasive example around -
you want to sacrifice proven (to avoid the word 'standard') query
language implementations to provide an own 'exotic' implementation ?
This doesn't make any sense to me except that it might be more fun to
write such an implementation
as to fix all outstanding JIRA issues.
Hibernate HQL is documented on ~30 printed pages with quite some examples:
http://docs.jboss.org/hibernate/core/3.3/reference/en/html/queryhql.html So? Java
EE is also documented. That doesn't mean we should use it... We should use what fits
our needs. We've already talked a LOT in the past about HQL and listened to a *LOT* of
users telling us it's hard to use. This is what drove the creation of XWQL a few years
ago.
Can you please point me to a document that explains XWQL - its
abstraction details considering XWikis Meta data model, the differences
to HQL or JPQL other than the trivial examples shown here:
http://incubator.myxwiki.org/xwiki/bin/view/XWQL/WebHome
From this document
http://platform.xwiki.org/xwiki/bin/view/DevGuide/QueryGuide
it seems to me that XWQL does ~some undocumented magic due to XWikis
meta data-model that might be reasonable or not - but where is the
explanation ?
The HQL
chapter in Gavin King and Christian Bauers 'standard' 'Java
Persistence' book is about 50 pages long.
Both documentations sort of scratch the surface - they are still lacking
when it comes to writing real complex stuff.
aggregations / joins all the like ...
So - now you propagate a new QL.
What new QL? Are you talking about XWQL (it's
several years old)? Or are you talking about Caleb's suggestion to add support for an
existing well known QL instead?
Yes - sorry I mean XWQL - HQL is supported already and IMO that's
sufficient although I may not be entitled to say that.
Maybe it
is better - who knows ?
It's not useful if there is just a basic documentation.
Even with a very good documentation it needs to be learned and understood.
From the users point of view it would be more beneficial to focus
efforts on making XWiki more concise.
Just as an example this issue
http://jira.xwiki.org/jira/browse/XRENDERING-75
seems to be open since 2 years ...
This is a bad example. This issue has been
there for 2 years because it's not really needed!
Well - it's flagged as
*MAJOR* . Are you saying that JIRA priority
statements are meaningless and nobody doesn't care anyway ?
Macros already support parameters and in addition
format parameters are supported for inline and if you need them for standalone it's
also possible using groups:
(% ... %)(((
{{macro/}}
)))
Again - another 'pitfall' in my eyes (at least in terms of documentation)
I've learned that this artifact always renders to wrapping the macro in
<div> {{macro}}</div> enclosures
instead of passing any parameters
(% ... %) (((
{{macro}}
)))
but this artifact (inline) passes parameters to the macro
(% ... %) {{macro}}
while this artifact (standalone) is not supported (not needed ?)
(% ... %)
{{macro}}
That's what I mean that from a users POV XWiki might well deserve to
become more 'concise'.
Again I
don't mean to criticize. But from time to time please try to see
your work through users glasses ...
I think you're mistaken about a few things
here:
1) this is a discussion started by someone. We're not refusing discussions be them
from users, contributors or committers. Nothing has been agreed. Why would we close
discussions and told people to shut up because they're not talking about something
that one user considers not useful?
2) why do you say we (as in xwiki committers) don't see through "user
glasses". We keep doing this all the time. Look around at all the issues that are
closed every day and that are user specific.
3) Developers need to think about a lot more things than you have to think about as a
user: stability of the platform, performance, api design (since it's a web development
platform), maintenance, etc. We need to think a few years ahead of users. With a reasoning
like "we fix only user stuff and don't do anything not directly
user-related" you wouldn't have a lot of things you like in xwiki and we would be
lagging behind other wikis.
So please don't generalize. If you have a specific wish/need please state it. You
mentioned XRENDERING-75 above and I've answered you (I already did on another thread
btw).
Thanks
-Vincent
Anyway, I'd like to say *THANK YOU* for the passion and supportive
attitude here on the list.
kind regards
Andreas
regards
Andreas
Am 04.04.2011 16:37, schrieb Caleb James DeLisle:
> On 04/04/2011 10:01 AM, Sergiu Dumitriu wrote:
>> On 04/02/2011 02:22 PM, Caleb James DeLisle wrote:
>>> After searching through documentation on JPQL (JPA's query language) I
was unable to find any
>>> example of the "doc.object(XWiki.XWikiUsers)" construct. This means
XWQL is it's own standard and
>>> there is no authoritative reference on it. What makes an implementation
compliant? I have found that
>>> most HQL queries can be executed as XWQL queries with little or no
modification so if compliance is
>>> defined as being "just like the reference implementation" then
nearly all HQL must be implemented in
>>> order to be compliant.
>> The goal of XWQL was to not be bound to a certain query language, but to
>> be able to map it to as many QLs as possible, be they SQL-related, like
>> HQL or JPQL, or other types of queries, like QBE, XPath, SPARQL. So, it
>> wasn't meant from the start to be compatible with any standard.
> The problem now is we don't have any specification to tell us what is valid and
what is not.
> Is this a valid XWQL query?
>
> $services.query.xwql("from BaseObject as obj where doc.fullName = obj.name and
obj.className =
> 'XWiki.XWikiUsers'").execute()
>
> Run it and you might be surprised.
> Based on that, we have no way of ensuring that a query which works now will work in a
new XWQL
> implementation which defeats the purpose of abstracting the user away from HQL.
>
>> Now, I'm not sure if the right thing to do is to move to a standard
>> query language, or to stick with our own.
> If we're going to define our own query language (I think there are enough
already) there are certain
> things we have to do such as writing a specification. I frankly find this thing
embarrassing.
>
>> - Is there any tool that allows mapping a JPQL or JDOQL query into other
>> query languages?
>
http://www.datanucleus.org/products/accessplatform_3_0/datastores.html
> These folks are mapping JDOQL and JPQL into a whole bunch of different types of
storage.
>
>> - Is there a way to parse a query into a tree/AST?
>> - Other than the fact that it's a non-standard language (and all the
>> consequences of this, like no support from tools and libraries), are
>> there any downsides to having our own query language?
> This particular one has 2 downsides:
> 1. There is no official specification.
> 2. HQL can be run as shown above.
>
> The major downside of implementing one correctly is that it is massively
complicated.
>
> Caleb
>
>> The benefit of XWQL was that it allowed to write domain specific
>> queries, which are shorter and easier to understand (at least in theory).
>>
>>> Looking at the specifications I have rewritten the example query in compliant
JPQL and JDOQL.
>>> I wrote these so that they would work if all objects were custom mapped which
is similar to the
>>> appearance XWQL gives.
>>>
>>> XWQL:
>>> (SELECT doc.fullName FROM XWikiDocument as doc) where doc.author =
'XWiki.LudovicDubost' and
>>> doc.object(XWiki.XWikiUsers).email like '%xwiki.com'
>>>
>>> JPQL:
>>> SELECT doc.fullName FROM XWikiDocument as doc, IN(doc.xObjects) obj WHERE
obj.className =
>>> 'XWiki.XWikiUsers' and obj.email LIKE '%xwiki.com'
>>>
>>> JDOQL:
>>> SELECT this.fullName FROM XWikiDocument WHERE
this.xObjects.containsValue(obj)&& obj.className ==
>>> "XWiki.XWikiUsers"&&
obj.email.startsWith("xwiki.com")
>>>
>>>
>>> I understood that XWQL was simply a translation scheme which made it appear
that we were using JPQL
>>> with the schema we wanted when really we were using HQL with the schema we
had. Given that it is not
>>> compliant JPQL that is not the case.
>>>
>>> I think when we update the schema, we should cut our losses with this thing
and move to something
>>> which has a reference document and is more widely used.
>>>
>>> WDYT?
>>>
>>> Caleb
>>>
>>>
>>>
>>> The JPQL specification (originally called EJBQL):
>>> ejb-3_0-fr-spec-ejbcore.pdf chapter 9.
>>>
http://jcp.org/aboutJava/communityprocess/final/jsr220/
>>>
>>> The JDOQL specification:
>>> jdo-3_0-mrel3-spec.pdf chapter 26.
>>>
http://db.apache.org/jdo/specifications.html
>>>
>>> Easy to read, example rich descriptions:
>>>
http://www.datanucleus.org/products/accessplatform_3_0/jpa/jpql.html
>>>
http://www.datanucleus.org/products/accessplatform_3_0/jdo/jdoql.html
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