[hibernate-dev] Re: [Hibernate-JIRA] Commented: (HSEARCH-115) Add a default value for indexing null value
Sanne Grinovero
sanne.grinovero at gmail.com
Mon Apr 21 21:29:18 EDT 2008
Hey all,
nice discussion :-)
About implementation 1:
I like this one, but think this is what people already are doing using
their own StringBridge when needed, as an "unsupported hack".
In case the framework was offering me this option I would expect it to
be really smart: "escape" somehow the value if eventually some
non-null object is tokenized to my same marker string; I would also
expect the framework to be keyword-aware somehow on query parsing, but
this looks really messy.
A new proposal:
I got inspired by the "3VL" considerations described in Emmanuel's
link to wikipedia, and think backwards compatibility is nice:
add a "@IndexNullMarker" on the property, this will add an additional
Field to the index for null values:
@Field
@IndexNullMarker
String getFoo(){
would add either the Field "foo:value" or "fooIsNull:true" to the
Document, implementing real three-state logic. Eventually we could add
"fooIsNull:false" too for query consistency.
To resolve nameclashes (imagine a getFooIsNull() property we could use
some character prohibited in Java identifiers:
"foo-isNull:true"
or escape the name with additional prefixes as needed.
The Field and StringBridge API would remain as-is;
If you prefer not to add an additional @IndexNullMarker could be
dropped if you think adding this field is acceptable for all fields.
We could add an additional option to existing field, but I am thinking
of a case you don't want to index the value, only mark it if it is
null.
Also IMHO an additional annotation makes it more intuitive that you
are adding an additional Field.
In any case I would question the original reason for this improvement
to index null values as "default language"; if there is a default I
think you should better tell me which it is, or give it a value. So I
can't really think of a good reason to have different results for
"search-on-null" rather than "search-on-empty", but it could
potentially help in "entity state reconstruction" use cases, when the
entity is partially rebuild using projection.
regards,
Sanne
2008/4/21, Emmanuel Bernard <emmanuel at hibernate.org>:
> 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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>
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