# On the need to reindex after upgrade **URL:** \ **Category:** Elasticsearch\ **Created:** [October 18, 2013, 7:50pm UTC](https://discuss.elastic.co/t/on-the-need-to-reindex-after-upgrade/14021 "2013-10-18T19:50:35Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![patokar](https://avatars.discourse-cdn.com/v4/letter/p/9de053/32.png) [@patokar](https://discuss.elastic.co/u/patokar)\ **Post date:** [October 18, 2013, 7:50pm UTC](https://discuss.elastic.co/t/on-the-need-to-reindex-after-upgrade/14021/1 "2013-10-18T19:50:35Z")
Hi, Looking for guidance, general tips about when should we reindex on upgrade. According to posts When do I need to reindex data?[https://groups.google.com/d/msg/elasticsearch/QtRD\_4eJjig/boAX0TnvovkJ](https://groups.google.com/d/msg/elasticsearch/QtRD_4eJjig/boAX0TnvovkJ), - Lucene is backward compatible within one version - Lucene 4.0 has an emulation layer that makes it safe to work with version 3. - "full cluster restart" in release notes means we just need to stop the whole cluster, then index will be opened on restart ... no need to re-index So, what are your suggestions/tips on this? Any specifics on Lucene/ES version diff ? Any section or warning in Release notes to look for? Maybe a FAQ entry covering this topic? Thanks in advance, --Patricio p.s.: I will be upgrading from 0.20.5 to 0.90.5, and have no plan to change index settings, type/fields mappings, nor use new features. We will be testing the old index once upgraded, any tips you have in mind? -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). For more options, visit [https://groups.google.com/groups/opt\_out](https://groups.google.com/groups/opt_out). ---
**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, 2:11am UTC](https://discuss.elastic.co/t/on-the-need-to-reindex-after-upgrade/14021/2 "2017-07-06T02:11:42Z")