In previous versions of Elasticsearch, JSON documents were allowed to contain unquoted field names.
This feature was removed in the 5.x series, but a backwards-compatibility layer was added via the
elasticsearch.json.allow_unquoted_field_names. This backwards-compatibility layer
has been removed in Elasticsearch 6.0.0.
In previous versions of Elasticsearch, documents were allowed to contain duplicate keys. Elasticsearch 6.0.0 enforces that all keys are unique. This applies to all content types: JSON, CBOR, Yaml and Smile.
In previous versions of Elasticsearch, having a proper Content-Type for the data in a request was not enforced. Elasticsearch 6.0.0 enforces that all requests with a body must have a supported Content-Type and this type will be used when parsing the data.
When using the
source query string parameter, the
source_content_type parameter must also be specified with
the media type of the source.
All REST APIs parameters (both request parameters and JSON body) support providing boolean "false" as the
false and boolean "true" as the value
true. All other values will raise an error.
The deprecated request parameters and plain text in request body has been removed. Define parameters in request body.
allow_no_indices options are no longer accepted
as they could cause undesired results when their values differed from their
ttl are not accepted anymore as parameters of index/update
Refresh requests that are broadcast to multiple shards that can have one or more shards fail during the request now return a 500 response instead of a 200 response in the event there is at least one failure.
In previous versions of Elasticsearch, delete by query requests without an explicit query were accepted, match_all was used as the default query and all documents were deleted as a result. From version 6.0.0, delete by query requests require an explicit query.