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https://issues.apache.org/jira/browse/LUCENE-10650?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17566422#comment-17566422
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Adrien Grand commented on LUCENE-10650:
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Indeed Elasticsearch would change the after effect to `L` instead of `no` to
work around the fact that Lucene removed support for `no`. You may not need to
reindex, I believe it would be possible to close your index, update settings to
use this new scripted similarity, and then open the index again to make the
change effective (I did not test this).
> "after_effect": "no" was removed what replaces it?
> --------------------------------------------------
>
> Key: LUCENE-10650
> URL: https://issues.apache.org/jira/browse/LUCENE-10650
> Project: Lucene - Core
> Issue Type: Wish
> Reporter: Nathan Meisels
> Priority: Major
>
> Hi!
> We have been using an old version of elasticsearch with the following
> settings:
>
> {code:java}
> "default": {
> "queryNorm": "1",
> "type": "DFR",
> "basic_model": "in",
> "after_effect": "no",
> "normalization": "no"
> }{code}
>
> I see [here|https://issues.apache.org/jira/browse/LUCENE-8015] that
> "after_effect": "no" was removed.
> In
> [old|https://github.com/apache/lucene-solr/blob/releases/lucene-solr/5.5.0/lucene/core/src/java/org/apache/lucene/search/similarities/BasicModelIn.java#L33]
> version score was:
> {code:java}
> return tfn * (float)(log2((N + 1) / (n + 0.5)));{code}
> In
> [new|https://github.com/apache/lucene-solr/blob/releases/lucene-solr/8.11.2/lucene/core/src/java/org/apache/lucene/search/similarities/BasicModelIn.java#L43]
> version it's:
> {code:java}
> long N = stats.getNumberOfDocuments();
> long n = stats.getDocFreq();
> double A = log2((N + 1) / (n + 0.5));
> // basic model I should return A * tfn
> // which we rewrite to A * (1 + tfn) - A
> // so that it can be combined with the after effect while still guaranteeing
> // that the result is non-decreasing with tfn
> return A * aeTimes1pTfn * (1 - 1 / (1 + tfn));
> {code}
> I tried changing {color:#172b4d}after_effect{color} to "l" but the scoring is
> different than what we are used to. (We depend heavily on the exact scoring).
> Do you have any advice how we can keep the same scoring as before?
> Thanks
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