# Question about the future release of ES that incorporate Lucene 7.0

**URL:** <https://discuss.elastic.co/t/question-about-the-future-release-of-es-that-incorporate-lucene-7-0/80163>\
**Category:** Elasticsearch\
**Created:** [March 27, 2017, 3:53pm UTC](https://discuss.elastic.co/t/question-about-the-future-release-of-es-that-incorporate-lucene-7-0/80163 "2017-03-27T15:53:09Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Ramdev\_Wudali](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/ramdev_wudali/32/7894_2.png) [@Ramdev\_Wudali](https://discuss.elastic.co/u/Ramdev_Wudali)\
**Post date:** [March 27, 2017, 3:53pm UTC](https://discuss.elastic.co/t/question-about-the-future-release-of-es-that-incorporate-lucene-7-0/80163/1 "2017-03-27T15:53:10Z")

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Hi :  
I was just reading Lucene's blog on Changes in Lucene 7.0, Since its on the roadmap for ES releases to include that, I was wondering what is the impact of moving away from TF/IDF to BM25 for scoring. For applications that are using the current TF/IDF based scoring for documents, how will it change docs rankings . specifically, for regression tests that might use some sort of ordering of the docs in the results.

Ramdev

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**Author:** ![softwaredoug](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/softwaredoug/32/22681_2.png) [@softwaredoug](https://discuss.elastic.co/u/softwaredoug)\
**Post date:** [March 27, 2017, 5:20pm UTC](https://discuss.elastic.co/t/question-about-the-future-release-of-es-that-incorporate-lucene-7-0/80163/2 "2017-03-27T17:20:50Z")

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BM25 is the default in Elasticsearch 5.0+

In general you should see ranking improvements. BM25 is just a better way  
of doing TF_IDF. I think some specialized use cases classic Lucene TF_IDF  
can be easier to reason about.

I wrote quite a bit about BM25 vs TF\*IDF in Lucene-base search here

> **[BM25 The Next Generation of Lucene Relevance](http://opensourceconnections.com/blog/2015/10/16/bm25-the-next-generation-of-lucene-relevation/)**
>
> There’s something new cooking in how Lucene scores documents. Instead of the traditional ‘TF\*IDF’ Lucene just switched to something called BM25 in trunk. Tha...

Doug

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**Author:** ![Ramdev\_Wudali](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/ramdev_wudali/32/7894_2.png) [@Ramdev\_Wudali](https://discuss.elastic.co/u/Ramdev_Wudali)\
**Post date:** [March 27, 2017, 5:59pm UTC](https://discuss.elastic.co/t/question-about-the-future-release-of-es-that-incorporate-lucene-7-0/80163/3 "2017-03-27T17:59:49Z")

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Thanks Doug. I think you answered my quetsion, (being BM25 is just a different way of doing TF\*IDF) that said, would it actually cause documents to be ranked in a different order (I am guessing yes,) If so Should regresion tests that depend on ordering based on scores be changed ?

Cheers

Ramdev

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**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [April 24, 2017, 5:59pm UTC](https://discuss.elastic.co/t/question-about-the-future-release-of-es-that-incorporate-lucene-7-0/80163/4 "2017-04-24T17:59:58Z")

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