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https://issues.apache.org/jira/browse/LUCENE-6590?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15324427#comment-15324427
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Adrien Grand commented on LUCENE-6590:
--------------------------------------
I just downloaded Solr 5.5 and indexed a couple documents with a "foo" field,
then ran a query on "foo:bar", the explanation shows that the idf is taken into
account only once:
{noformat}
1.4519851 = weight(foo:bar in 0) [ClassicSimilarity], result of:
1.4519851 = fieldWeight in 0, product of:
1.0 = tf(freq=1.0), with freq of:
1.0 = termFreq=1.0
1.4519851 = idf(docFreq=6, maxDocs=11)
1.0 = fieldNorm(doc=0)
{noformat}
> Explore different ways to apply boosts
> --------------------------------------
>
> Key: LUCENE-6590
> URL: https://issues.apache.org/jira/browse/LUCENE-6590
> Project: Lucene - Core
> Issue Type: Wish
> Reporter: Adrien Grand
> Priority: Minor
> Fix For: 5.4
>
> Attachments: LUCENE-6590.patch, LUCENE-6590.patch, LUCENE-6590.patch,
> LUCENE-6590.patch, LUCENE-6590.patch, LUCENE-6590.patch, LUCENE-6590.patch
>
>
> Follow-up from LUCENE-6570: the fact that all queries are mutable in order to
> allow for applying a boost raises issues since it makes queries bad cache
> keys since their hashcode can change anytime. We could just document that
> queries should never be modified after they have gone through IndexSearcher
> but it would be even better if the API made queries impossible to mutate at
> all.
> I think there are two main options:
> - either replace "void setBoost(boost)" with something like "Query
> withBoost(boost)" which would return a clone that has a different boost
> - or move boost handling outside of Query, for instance we could have a
> (immutable) query impl that would be dedicated to applying boosts, that
> queries that need to change boosts at rewrite time (such as BooleanQuery)
> would use as a wrapper.
> The latter idea is from Robert and I like it a lot given how often I either
> introduced or found a bug which was due to the boost parameter being ignored.
> Maybe there are other options, but I think this is worth exploring.
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