Mapping changes

Previously, Elasticsearch recognized the strings true, false, on, off, yes, no, 0, 1 as booleans. Elasticsearch 6.0 recognizes only the strings true and false as booleans and will throw an error otherwise. For backwards compatibility purposes, during the 6.x series the previous coercion rules will continue to work on pre-6.0 indices. This means that you do not need to change affected existing mappings immediately. However, it is not possible to create new indices from existing index templates that violate the strict boolean coercion rules.

On new mappings, the _all meta field that contains a copy of the text from each field is now disabled by default. The query_string and simple_query_string queries that previously used _all to search will now check if _all is enabled/disabled and switch to executing the query across all fields if _all is disabled. _all can no longer be configured for indices created with Elasticsearch version 6.0 or later.

Since the _all field is now disabled by default and cannot be configured for indices created with Elasticsearch 6.0 or later, the include_in_all setting is now disallowed for these indices' mappings.

Previously Elasticsearch would silently ignore any dynamic templates that included a match_mapping_type type that was unrecognized. An exception is now thrown on an unrecognized type.

The locale option of date fields previously allowed almost any string values, and unrecognized values would simply be ignored. Unrecognized values are now rejected on indices created with Elasticsearch 6.0 or newer.