Document index.lossy.source-mapping-parameters setting

Author: romseygeek

docs/reference/elasticsearch/index-settings/source.md

@@ -22,3 +22,7 @@ $$$synthetic-source-keep$$$
 
 `index.mapping.synthetic_source_keep`
 : (Static, string) Controls how to retain accuracy of fields at the index level. Valid values are `none` or `arrays`.This is a subset of [synthetic source keep mapping attribute](/reference/elasticsearch/mapping-reference/mapping-source-field.md#synthetic-source-keep). Defaults to `arrays` if `index.mode` is `logsdb` or otherwise `none`.
+
+$$$index-lossy-source_mapping_parameters$$$
+
+`index.lossy.source-mapping-parameters` {applies_to}`stack: ga 8.14` {applies-to}`serverless: all`: (Static, boolean) Indicates whether [source include/excludes](/reference/elasticsearch/mapping-reference/mapping-source-field.md#include-exclude) are permitted. Defaults to `true` in {{stack}} and `false` in {{serverless-short}}.

docs/reference/elasticsearch/mapping-reference/mapping-source-field.md

@@ -356,6 +356,7 @@ An expert-only feature is the ability to prune the contents of the `_source` fie
 Removing fields from the `_source` has similar downsides to disabling `_source`, especially the fact that you cannot reindex documents from one Elasticsearch index to another. Consider using [source filtering](/reference/elasticsearch/rest-apis/retrieve-selected-fields.md#source-filtering) instead.
 ::::
 
+If the [`index.lossy.source-mapping-parameters`](/reference/elasticsearch/index-settings/source.md#index-lossy-source_mapping_parameters) settings is `false` then these parameters cannot be configured.
 
 The `includes`/`excludes` parameters (which also accept wildcards) can be used as follows: