Nathan Meisels created LUCENE-10650:
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Summary: "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
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 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:
long N = stats.getNumberOfDocuments();
long n = stats.getDocFreq();
double A = log2((N + 1) / (n + 0.5));
// basic model I(n) 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));
I tried changing 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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