# Is rerunning elasticsearch equivalent to rebuilding index?

**URL:** <https://discuss.elastic.co/t/is-rerunning-elasticsearch-equivalent-to-rebuilding-index/2234>\
**Category:** Elasticsearch\
**Created:** [June 9, 2015, 4:14pm UTC](https://discuss.elastic.co/t/is-rerunning-elasticsearch-equivalent-to-rebuilding-index/2234 "2015-06-09T16:14:44Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![harry747747](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/harry747747/32/483_2.png) [@harry747747](https://discuss.elastic.co/u/harry747747)\
**Post date:** [June 9, 2015, 4:14pm UTC](https://discuss.elastic.co/t/is-rerunning-elasticsearch-equivalent-to-rebuilding-index/2234/1 "2015-06-09T16:14:44Z")

</div>

I changed similarity measure for retrieving documents. The documentation says I need to rebuild the index. Is rebuilding the index equivalent to rerunning the elasticsearch in /bin ?  
Actually, I tried rerun the elasticsearch, it does change the retrieval document results. Don't know if it is the right way.

---

<div class="post-metadata">

**Author:** ![warkolm](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/warkolm/32/39224_2.png) [@warkolm](https://discuss.elastic.co/u/warkolm)\
**Post date:** [June 9, 2015, 9:25pm UTC](https://discuss.elastic.co/t/is-rerunning-elasticsearch-equivalent-to-rebuilding-index/2234/2 "2015-06-09T21:25:56Z")

</div>

You need to delete the data from ES and then index it again.

---

<div class="post-metadata">

**Author:** ![harry747747](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/harry747747/32/483_2.png) [@harry747747](https://discuss.elastic.co/u/harry747747)\
**Post date:** [June 10, 2015, 8:06pm UTC](https://discuss.elastic.co/t/is-rerunning-elasticsearch-equivalent-to-rebuilding-index/2234/3 "2015-06-10T20:06:30Z")

</div>

I changed the elasticsearch.yml file, and added index.similairty.default.type: BM25, and rerun the elasticsearch executable file. Is it the right way to change similarity measure?  
My data are very big, I don't want to re index the data.

---

<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [July 6, 2017, 12:08am UTC](https://discuss.elastic.co/t/is-rerunning-elasticsearch-equivalent-to-rebuilding-index/2234/4 "2017-07-06T00:08:28Z")

</div>