[infinispan-dev] Infinispan Query entity discovery (Was: Re: new Infinispan Query API - ISPN-194)

[Emmanuel Bernard]

Users can put indexed or nit indexed superclasses in the query target type. That would not work for you as you can't discover known subtypes wo scanning or having a closure of types somewhere. 



On 26 avr. 2011, at 23:32, Sanne Grinovero <sanne.grinovero at gmail.com> wrote:

> Hello,
> I'm forking off this thread, as we never resolved how to cope with the
> main issue:
> 
> how is Infinispan Query going to be aware of which entities are to be
> considered as default targets for a Query?
> 
> the realistic ideas so far:
> A) class scanning: seems nobody liked this idea, but I'll still
> mention it as the other options aren't looking great either.
> B) scan known indexes (need to define what the "known indexes" are as
> we usually infer that from the classes)
>   -- could enforce a single index
> C) have to list all fully qualified class names in the configuration
> D) don't care: consider it a good practice to specify all targeted
> types when performing a Query.
> E) please suggest :)
> 
> The currently implemented solution is D, as it requires no coding at all :)
> considering the simplicity of it I'm liking it more the more I think
> about it; I could even polish the approach by adding a single line to
> log a warning when the user doesn't respect the best practice, or to
> mandate it.
> 
> Considering that when a Query is invoked specifying the target types
> there is no doubt we know the classes, I could add a warning in case
> the Query is performed without specifying the type: in that case it
> usually implies the query targets all known types, which is always
> fine when using Hibernate Search, but could be inconsistent with
> Infinispan Query as it might not have discovered all types yet (1), so
> a very simple solution is to mandate the type parameter.
> 
> [1] - when the Cache interceptor hits an event adding a new type, the
> Search engine is reconfigured.
> 
> thoughts?
> 
> Sanne
> 
> 
> 2011/4/5 Emmanuel Bernard <emmanuel at hibernate.org>:
>> 
>> On 5 avr. 2011, at 13:38, Sanne Grinovero wrote:
>> 
>>> 2011/4/5 Emmanuel Bernard <emmanuel at hibernate.org>:
>>>> 
>>>> On 5 avr. 2011, at 12:20, Galder Zamarreño wrote:
>>>> 
>>>>> 
>>>>> On Apr 4, 2011, at 6:23 PM, Sanne Grinovero wrote:
>>>>> 
>>>>>> </snip>
>>>>>> 
>>>>>> there's one catch:
>>>>>> when searching for a class type, it will only include results from
>>>>>> known subtypes. The targeted type is automatically added to the known
>>>>>> classes, but eventually existing subtypes are not discovered.
>>>>>> 
>>>>>> Bringing this issue to an extreme, if the query is not targeting any
>>>>>> type, and no indexed types where added to the grid (even if some exist
>>>>>> already as they might have been inserted by other JVMs or previous
>>>>>> runs), all queries will return no results.
>>>>>> How to solve this?
>>>>>> - class scanning?
>>>>> 
>>>>> Nope, too expensive.
>>>>> 
>>>>>> - explicitly list indexed entities in Infinispan configuration?
>>>>> 
>>>>> No
>>>>> 
>>>>>> - a metadata cache maintaining a distributed&stored copy of known types
>>>>> 
>>>>> That sounds more appealing. It could be a good middle ground until Search can search for types.
>>>> 
>>>> Do you have any specific idea in mind?
>>>> 
>>>> To magically find types:
>>>>  - we scan every file system, databases, caches available to the app and look for Lucene metadata => unrealistic
>>>>  - there is some kind of convention on where the indexes are and we do index scanning at startup => scanning are very likely to be slower that class scanning (potential remote access, bigger dataset etc)
>>>>  - we enforce one or a fixed number of Lucene indexes for all data in Infinispan => not sure that's a good idea but this can be explored
>>>>  - we somehow ask the framework using HSearch to fill up classes
>>>> 
>>>> other approaches?
>>> 
>>> why was class scanning discarded in the first answer? as H. Search can
>>> auto-discover classes by working on top of JPA entity autodiscovery, I
>>> guess that each application node could look into it's own known
>>> classpath.
>>> After all if some type is not visible to him as it was added from
>>> another node from a different app, he won't be able to return
>>> instances of it either.
>>> We could face the opposite problem of building metadata of classes
>>> people doesn't mean to index in this cache.
>> 
>> Right. scanning (class or index) will be a bit aggressive and could build unneeded metadata (or even worse, return unexpected classes).