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From "Kaleem Ahmed (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SOLR-2953) Introducing hit Count as an alternative to score
Date Thu, 08 Dec 2011 06:59:39 GMT

    [ https://issues.apache.org/jira/browse/SOLR-2953?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13165050#comment-13165050
] 

Kaleem Ahmed commented on SOLR-2953:
------------------------------------

I don't think changing the similarity does it all.. refer this link 
http://lucene.apache.org/java/2_9_0/api/core/org/apache/lucene/search/package-summary.html#changingSimilarity

it says
{quote}

Changing Scoring — Expert Level

Changing scoring is an expert level task, so tread carefully and be prepared to share your
code if you want help.

With the warning out of the way, it is possible to change a lot more than just the Similarity
when it comes to scoring in Lucene. Lucene's scoring is a complex mechanism that is grounded
by three main classes:

    Query — The abstract object representation of the user's information need.
    Weight — The internal interface representation of the user's Query, so that Query objects
may be reused.
    Scorer — An abstract class containing common functionality for scoring. Provides both
scoring and explanation capabilities.{quote}
 I mainly changed the scorers and query classes of different queries to achieve it
                
> Introducing hit Count as an alternative to score 
> -------------------------------------------------
>
>                 Key: SOLR-2953
>                 URL: https://issues.apache.org/jira/browse/SOLR-2953
>             Project: Solr
>          Issue Type: New Feature
>          Components: search
>    Affects Versions: 4.0
>            Reporter: Kaleem Ahmed
>              Labels: features
>             Fix For: 4.0
>
>   Original Estimate: 1,008h
>  Remaining Estimate: 1,008h
>
> As of now we have score as relevancy factor for a query against a document, and this
score is relative to the number of documents in the index. In the same way why not have some
other relevancy feature say "hitCounts" which is absolute for a given doc and a given query,
It shouldn't depend on the number of documents in the index. This will help a lot for the
frequently changing indexes , where the search rules are predefined along the relevancy factor
for a document to be qualified for that query(search rule). 
> Ex: consider a use case where a list of queries are formed with a threshold number for
each query and these are searched on a frequently updated index to get the documents that
score above the threshold i.e. when a document's relevancy factor crosses the threshold for
a query the document is said to be qualified for that query. 
> For the above use case to satisfy the score shouldn't change every time the index gets
updated with new documents. So we introduce new feature called "hitCount"  which represents
the relevancy of a document against a query and it is absolute(won't change with index size).

> This hitCount is a positive integer and is calculated as follows 
> Ex: Document with text "the quick fox jumped over the lazy dog, while the lazy dog was
too lazy to care" 
> 1. for the query "lazy AND dog" the hitCount will be == (no of occurrences of "lazy"
in the document) +  (no of occurrences of "dog" in the document)  =>  3+2 => 5  
> 2. for the phrase query  \"lazy dog\"  the hitCount will be == (no of occurrences of
exact phrase "lazy dog" in the document) => 2
> This will be very useful  as an alternative scoring mechanism.
> I already implemented this whole thing in the Solr source code(that I downloaded) and
we are using it. So far it's going good. 
> It would be really great if this feature is added to trunk (original  Solr) so that we
don't have to implement the changes every time  a new version is released and also others
could be benefited with this.     

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