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https://issues.apache.org/jira/browse/LUCENE-9269?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17056205#comment-17056205
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Adrien Grand commented on LUCENE-9269:
--------------------------------------
For this particular issue, I think that the right fix would be to fix
{{TermQuery#equals}} and {{hashCode}} to take {{perReaderTermState}} into
account. Queries shouldn't be considered equal if they might return different
scores. I don't think that this would have bad side-effects as boolean rewrites
are generally used for scoring queries, which are not cached (which is the
other typicall call-site for Query#equals/hashCode).
> Blended queries with boolean rewrite can result in inconstitent scores
> ----------------------------------------------------------------------
>
> Key: LUCENE-9269
> URL: https://issues.apache.org/jira/browse/LUCENE-9269
> Project: Lucene - Core
> Issue Type: Bug
> Components: core/search
> Affects Versions: 8.4
> Reporter: Michele Palmia
> Priority: Minor
> Attachments: LUCENE-9269-test.patch
>
>
> If two blended queries are should clauses of a boolean query and are built so
> that
> * some of their terms are the same
> * their rewrite method is BlendedTermQuery.BOOLEAN_REWRITE
> the docFreq for the overlapping terms used for scoring is picked as follow:
> # if the overlapping terms are not boosted, the df of the term in the first
> blended query is used
> # if any of the overlapping terms is boosted, the df is picked at (what
> looks like) random.
> A few examples using a field with 2 terms: f:a (df: 2), and f:b (df: 3).
> {code:java}
> a)
> Blended(f:a f:b) Blended (f:a)
> df: 3 df: 2
> gets rewritten to:
> (f:a)^2.0 (f:b)
> df: 3 df:2
> b)
> Blended(f:a) Blended(f:a f:b)
> df: 2 df: 3
> gets rewritten to:
> (f:a)^2.0 (f:b)
> df: 2 df:2
> c)
> Blended(f:a f:b^0.66) Blended (f:a^0.75)
> df: 3 df: 2
> gets rewritten to:
> (f:a)^1.75 (f:b)^0.66
> df:? df:2
> {code}
> with ? either 2 or 3, depending on the run.
>
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