Also see Breaking changes in 7.1.
- Applying deletes or updates on an index after it has been shrunk may corrupt the index. In order to prevent this issue, it is recommended to stop shrinking read-write indices. For read-only indices, it is recommended to force-merge indices after shrinking, which significantly reduces the likeliness of this corruption in the case that deletes/updates would be applied by mistake. This bug is fixed in Elasticsearch 7.7 and later versions. More details can be found on the corresponding issue.
Indices created in 6.x with
date_nanosfields using formats that are incompatible with java.time patterns will cause parsing errors, incorrect date calculations or wrong search results. https://github.com/elastic/elasticsearch/pull/52555 This is fixed in Elasticsearch 7.7 and later versions.