[hibernate-dev] Re: [Hibernate-JIRA] Commented: (HSEARCH-115) Add a default value for indexing null value

[Emmanuel Bernard]

Hey
The more I think about the feature, the less I like it.

Here is what I have written in Hibernate Search in Action

Hibernate Search, by default, does not store null attributes into the  
index. Lucene does not have the notion of null fields, the field is  
simply not there. Hibernate Search could offer the ability (and most  
likely will in the future) to use a special string as a null marker to  
still be able to search by "null".
But before you jump at the Hibernate Search team throat, you need to  
understand why they have not offered this feature so far. Null is not  
a value per se. Null means that the data is not known (or does not  
make sense). Therefore, searching by null as if it was a value is  
somewhat odd. The authors are well aware that this is a raging debate  
especially amongst the relational model experts (see http://en.wikipedia.org/wiki/Null_%28SQL%29) 
.
Whenever you feel the need for searching by "null", you should ask  
yourself if storing a special marker value in the database would make  
more sense. If you store a special marker value in the database, a lot  
of the "null" inconsistencies vanish. It also has the side effect of  
being queriable in Lucene and Hibernate Search.

So before we jump on the boat for this feature, I would like to know  
if people think it's still a good idea to offer this feature.

To answer your questions, the reason why I do not pass @Field but the  
raw set of data is because the @Field.index is translated into it's  
Lucene representation: some work is done.
Most people will write StringBridge implementation anyway where the  
null handling will be taken care of transparently (by  
String2FieldBridgeAdaptor).

I think I like 1 or 3. Note that get should be changed as well. Three  
is interesting indeed, rename it IndexingStragegy.

On  Apr 21, 2008, at 10:07, Hardy Ferentschik wrote:
> Hi Emmanuel,
>
> what's you take on this? Just adding another String parameter will  
> work, but are we not getting too many parameters into the method?  
> Wouldn't it be nicer to pass the actual @Field annotation. I think  
> this might make things also clearer for the implementor of the  
> interface.
>
> I am also trying here to get a little into your head to understand  
> your ideas behind the code design - hope
> you don't mind ;-)
>
> --Hardy
>
>
>
> ------- Forwarded message -------
> From: "Hardy Ferentschik (JIRA)" <noreply at atlassian.com>
> To: hardy at ferentschik.de
> Subject: [Hibernate-JIRA] Commented: (HSEARCH-115) Add a default  
> value for indexing null value
> Date: Mon, 21 Apr 2008 14:04:33 +0200
>
>
>    [ http://opensource.atlassian.com/projects/hibernate/browse/HSEARCH-115?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_30032 
>  ]
>
> Hardy Ferentschik commented on HSEARCH-115:
> -------------------------------------------
>
> Ok, here are a few suggestions:
>
> 1. This is the simplest way. Basically just add a new property named  
> 'indexNullAs' to @Field and @ClassBridge. Accordingly extend the  
> FieldBridge interface to set(String name, Object value, Document  
> document, Field.Store store, Field.Index index, Field.TermVector  
> termVector, Float boost, String indexNullAs).
>
> 2. Alternatively one could change the FieldBridge API to actually  
> pass in the Field annotation itself: set(String name, Object value,  
> Document document, Field fieldAnnotation,  Float boost). This would  
> reduce the amount of parameters and might actually be more  
> transparent for users implementing custom bridges. Unfortunately,  
> one would have to introduce a ClassBridge interface as well in this  
> case. I am not sure whether it is a good design choice to pass  
> annotation instances around.
>
> 3. We ccould also change the API into something like this:  
> set(String name, Object value, Document document, IndexProperties  
> props), where IndexProperties is just a wrapper class for  
> Field.Store, Field.Index, ... The drawback is that this just  
> increases the number of classes.
>
> Any comments?
>
>> Add a default value for indexing null value
>> -------------------------------------------
>>
>>                Key: HSEARCH-115
>>                URL: http://opensource.atlassian.com/projects/hibernate/browse/HSEARCH-115
>>            Project: Hibernate Search
>>         Issue Type: Improvement
>>         Components: mapping
>>           Reporter: Julien Brulin
>>           Assignee: Hardy Ferentschik
>>            Fix For: 3.1.0
>>
>>
>> Hi,
>> Null elements are not indexed by lucene then it's not easy to use a  
>> nullable property in lucene query.
>> I have a TagTranslation entity in my model with a nullable property  
>> language. In this case null is used as default language for tag  
>> translation.
>> Each translation may have many variations like synonyms.
>> Because I can specified a default value for null value in the  
>> @Field annotation like this @Field(index=Index.UN_TOKENIZED,  
>> store=Store.NO, default='null'), i can't search a cat tag with a  
>> default translation like this : +value:cat* +lang:null
>> <pre></code>
>> @Entity()
>> @Table(name="indexing_tag_trans")
>> @org 
>> .hibernate 
>> .annotations 
>> .Cache 
>> (usage=org.hibernate.annotations.CacheConcurrencyStrategy.READ_WRITE)
>> @Indexed
>> public class TagTranslation implements java.io.Serializable {
>>
>>
>> 	private static final long serialVersionUID = -1065316566731456110L;
>> 	
>>    @Id
>>    @GeneratedValue(strategy=GenerationType.IDENTITY)
>>    @DocumentId
>>    private Integer id;
>>
>> 	@Field(index=Index.UN_TOKENIZED, store=Store.NO)
>>    private String language;
>>
>>    @Field(index=Index.TOKENIZED, store=Store.YES)
>>    private String value;
>>
>>    @OneToMany(cascade=CascadeType.ALL, fetch=FetchType.LAZY)
>>     
>> @org 
>> .hibernate 
>> .annotations.Fetch(org.hibernate.annotations.FetchMode.SUBSELECT)
>>    @JoinColumn(name="translation_id")
>>    @IndexedEmbedded
>>    private List<TagVariation> variations = new  
>> LinkedList<TagVariation>();
>>
>>    public TagTranslation() { }
>> ...
>> </code>
>> </pre>
>> What do you think about that ?
>> Ps: sorry for english write, i am a french guy.
>
>
>
> -- 
> Hartmut Ferentschik
> Ekholmsv.339 ,1, 127 45 Skärholmen, Sweden
> Phone:  +46 704 225 097 (m)

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