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From "Robert Muir (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-2876) Remove Scorer.getSimilarity()
Date Thu, 20 Jan 2011 14:06:05 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2876?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12984198#action_12984198
] 

Robert Muir commented on LUCENE-2876:
-------------------------------------

bq. You're right, I was for some reason under the impression that part of the reason for the
change is that Weight already exposes Similarity but it is not, and I think it shouldn't,
so current patch is good here.

Yes, mainly it was just to correct the inconsistencies:
* the base class does nothing with Similarity, and its often null, so i don't think it needs
to know about it.
* the base class does however, provide functionality that depends on Weight, and I think it
should be non-null to support that. We might want to expand on this functionality in the future
too.

I wish i could have thrown IAE on null Weight (I did this to find all scorers that did not
comply), but there is again
the one ValueSourceScorer in Solr that isn't easily fixed... at least the patch creates more
consistency.

I'll review all javadocs for the scorers, and try to make sure the param documentation is
up to date.

Thanks again for taking the time to review these scoring issues.


> Remove Scorer.getSimilarity()
> -----------------------------
>
>                 Key: LUCENE-2876
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2876
>             Project: Lucene - Java
>          Issue Type: Task
>          Components: Query/Scoring
>            Reporter: Robert Muir
>            Assignee: Robert Muir
>             Fix For: 3.1, 4.0
>
>         Attachments: LUCENE-2876.patch
>
>
> Originally this was part of the patch for per-field Similarity (LUCENE-2236), but I pulled
it 
> out here as its own issue as its really mostly unrelated. I also like it as a separate
issue 
> to apply the deprecation to branch_3x to just make less surprises/migration hassles for
4.0 users.
> Currently Scorer takes a confusing number of ctors, either a Similarity, or a Weight
+ Similarity.
> Also, lots of scorers don't use the Similarity at all, and its not really needed in Scorer
itself.
> Additionally, the Weight argument is often null. The Weight makes sense to be here in
Scorer, 
> its the parent that created the scorer, and used by Scorer itself to support LUCENE-2590's
features.
> But I dont think all queries work with this feature correctly right now, because they
pass null.
> Finally the situation gets confusing if you start to consider delegators like ScoreCachingWrapperScorer,
> which arent really delegating correctly so I'm unsure features like LUCENE-2590 aren't
working with this.
> So I think we should remove the getSimilarity, if your scorer uses a Similarity its already
coming
> to you via your ctor from your Weight and you can manage this yourself.
> Also, all scorers should pass the Weight (parent) that created them, and this should
be Scorer's only ctor.
> I fixed all core/contrib/solr Scorers (even the internal ones) to pass their parent Weight,
just for consistency
> of this visitor interface. The only one that passes null is Solr's ValueSourceScorer.
> I set fix-for 3.1, not because i want to backport anything, only to mark the getSimilarity
deprecated there.

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