[DOCS] Add dynamic runtime fields to docs (#66194)

docs/reference/mapping/dynamic/field-mapping.asciidoc

@@ -1,35 +1,37 @@
 [[dynamic-field-mapping]]
 === Dynamic field mapping
 
-By default, when a previously unseen field is found in a document,
-Elasticsearch will add the new field to the type mapping.   This behaviour can
-be disabled, both at the document and at the <<object,`object`>>  level, by
-setting the <<dynamic,`dynamic`>> parameter to `false` (to ignore new fields) or to `strict` (to throw
-an exception if an unknown field is encountered).
-
-Assuming `dynamic` field mapping is enabled, some simple rules are used to
-determine which data type the field should have:
-
-[horizontal]
-*JSON data type*::                   *Elasticsearch data type*
-
-`null`::                            No field is added.
-`true` or `false`::                 <<boolean,`boolean`>> field
-floating{nbsp}point{nbsp}number::   <<number,`float`>> field
-integer::                           <<number,`long`>> field
-object::                            <<object,`object`>> field
-array::                             Depends on the first non-`null` value in the array.
-string::                            Either a <<date,`date`>> field
-                                        (if the value passes <<date-detection,date detection>>),
-                                    a <<number,`double`>> or <<number,`long`>> field
-                                        (if the value passes <<numeric-detection,numeric detection>>)
-                                    or a <<text,`text`>> field, with a <<keyword,`keyword`>> sub-field.
-
-These are the only <<mapping-types,field data types>> that are dynamically
-detected.  All other data types must be mapped explicitly.
-
-Besides the options listed below, dynamic field mapping rules can be further
-customised with <<dynamic-templates,`dynamic_templates`>>.
+When {es} detects a new field in a document, it _dynamically_ adds the field to
+the type mapping. The <<dynamic,`dynamic`>> parameter controls this behavior.
+
+You can disable dynamic mapping, both at the document and at the
+<<object,`object`>> level. Setting the `dynamic` parameter to
+`false` ignores new fields, and `strict` rejects the document if {es}
+encounters an unknown field.
+
+When dynamic field mapping is enabled, {es} uses the following rules to
+determine how to map data types for each field.
+
+NOTE: These are the only <<mapping-types,field data types>> that {es} detects
+dynamically. All other data types must be mapped explicitly.
+
+[cols="3"]
+|===
+h| JSON data type h| `dynamic:true` h| `dynamic:runtime`
+ |`null` 2*| No field added
+ |`true` or `false` 2*| `boolean`
+ |floating point number | `float` | `double`
+ |`integer` 2*| `long`
+ |`object`<<dynamic-object-footnote,^1^>>  2*| `object`
+ |`array` 2*|  Depends on the first non-`null` value in the array
+ |`string` that passes <<date-detection,date detection>> 2*| `date`
+ |`string` that passes <<numeric-detection,numeric detection>> | `double` or `long` | `double`
+ |`string` that doesn't pass `date` detection or `numeric` detection | `text` with a `.keyword` sub-field | `keyword`
+3+| [[dynamic-object-footnote]] ^1^Objects are always mapped as part of the `properties` section, even when the `dynamic` parameter is set to `runtime`. | |
+|===
+
+Besides the following options, you can customize dynamic field mapping rules
+with <<dynamic-templates,`dynamic_templates`>>.
 
 [[date-detection]]
 ==== Date detection
@@ -129,4 +131,3 @@ PUT my-index-000001/_doc/1
 
 <1> The `my_float` field is added as a <<number,`float`>> field.
 <2> The `my_integer` field is added as a <<number,`long`>> field.
-

docs/reference/mapping/params/dynamic.asciidoc

@@ -1,24 +1,31 @@
 [[dynamic]]
 === `dynamic`
 
-By default, fields can be added _dynamically_ to a document, or to
-<<object,inner objects>> within a document, just by indexing a document
-containing the new field.  For instance:
+When you index a document containing a new field, {es} <<dynamic-mapping,adds the field dynamically>> to a document or to inner objects within a document. The
+following document adds the string field `username`, the object field
+`name`, and two string fields under the `name` object:
 
 [source,console]
---------------------------------------------------
-PUT my-index-000001/_doc/1 <1>
+----
+PUT my-index-000001/_doc/1
 {
   "username": "johnsmith",
-  "name": {
+  "name": { <1>
     "first": "John",
     "last": "Smith"
   }
 }
 
 GET my-index-000001/_mapping <2>
+----
+<1> Refer to fields under the `name` object as `name.first` and `name.last`.
+<2> Check the mapping to view changes.
+
+The following document adds two string fields: `email` and `name.middle`:
 
-PUT my-index-000001/_doc/2 <3>
+[source,console]
+----
+PUT my-index-000001/_doc/2
 {
   "username": "marywhite",
   "email": "[email protected]",
@@ -29,35 +36,24 @@ PUT my-index-000001/_doc/2 <3>
   }
 }
 
-GET my-index-000001/_mapping <4>
---------------------------------------------------
-
-<1> This document introduces the string field `username`, the object field
-    `name`, and two string fields under the `name` object which can be
-    referred to as `name.first` and `name.last`.
-<2> Check the mapping to verify the above.
-<3> This document adds two string fields: `email` and `name.middle`.
-<4> Check the mapping to verify the changes.
+GET my-index-000001/_mapping
+----
 
-The details of how new fields are detected and added to the mapping is explained in <<dynamic-mapping>>.
+TIP: Use the <<indices-put-mapping,PUT mapping API>> to update the `dynamic`
+setting on existing fields.
 
-The `dynamic` setting controls whether new fields can be added dynamically or
-not.  It accepts three settings:
+[[dynamic-inner-objects]]
+==== Setting `dynamic` on inner objects
+<<object,Inner objects>> inherit the `dynamic` setting from their parent
+object or from the mapping type. In the following example, dynamic mapping is
+disabled at the type level, so no new top-level fields will be added
+dynamically.
 
-[horizontal]
-`true`::    Newly detected fields are added to the mapping. (default)
-`false`::   Newly detected fields are ignored. These fields will not be indexed so will not be searchable 
-            but will still appear in the `_source` field of returned hits. These fields will not be added 
-            to the mapping,  new fields must be added explicitly.
-`strict`::  If new fields are detected, an exception is thrown and the document is rejected. New fields 
-            must be explicitly added to the mapping.
-
-The `dynamic` setting may be set at the mapping type level, and on each
-<<object,inner object>>.  Inner objects inherit the setting from their parent
-object or from the mapping type.  For instance:
+However, the `user.social_networks` object enables dynamic mapping, so you can
+add fields to this inner object.
 
 [source,console]
---------------------------------------------------
+----
 PUT my-index-000001
 {
   "mappings": {
@@ -68,20 +64,32 @@ PUT my-index-000001
           "name": {
             "type": "text"
           },
-          "social_networks": { <3>
-            "dynamic": true,
+          "social_networks": {
+            "dynamic": true, <3>
             "properties": {}
           }
         }
       }
     }
   }
 }
---------------------------------------------------
+----
 
-<1> Dynamic mapping is disabled at the type level, so no new top-level fields will be added dynamically.
+<1> Disables dynamic mapping at the type level.
 <2> The `user` object inherits the type-level setting.
-<3> The `user.social_networks` object enables dynamic mapping, so new fields may be added to this inner object.
+<3> Enables dynamic mapping for this inner object.
 
-TIP: The `dynamic` setting can be updated on existing fields
-using the <<indices-put-mapping,PUT mapping API>>.
+[[dynamic-parameters]]
+==== Parameters for `dynamic`
+The `dynamic` parameter controls whether new fields are added dynamically, and
+accepts the following parameters:
+
+[horizontal]
+`true`::    New fields are added to the mapping (default).
+`runtime`:: New fields are added to the mapping as <<runtime,runtime fields>>.
+            These fields are not indexed, and are loaded from `_source` at query time.
+`false`::   New fields are ignored. These fields will not be indexed
+            or searchable, but will still appear in the `_source` field of returned hits. These fields will not be added
+            to the mapping, and new fields must be added explicitly.
+`strict`::  If new fields are detected, an exception is thrown and the document
+            is rejected. New fields  must be explicitly added to the mapping.

docs/reference/mapping/runtime.asciidoc

@@ -6,7 +6,10 @@ add fields to existing documents. With _runtime fields_, you can add
 fields to documents already indexed to {es} without reindexing your data.
 
 You access runtime fields from the search API like any other field, and {es}
-sees runtime fields no differently.
+sees runtime fields no differently. You can define runtime fields in the
+<<runtime-mapping-fields,index mapping>> or in the
+<<runtime-search-request,search request>>. Your choice, which is part of the
+inherent flexibility of runtime fields.
 
 [discrete]
 [[runtime-benefits]]
@@ -83,6 +86,10 @@ script. If you define a runtime field without a script, {es} evaluates the
 field at search time, looks at each document containing that field, retrieves
 the `_source`, and returns a value if one exists.
 
+If <<dynamic-field-mapping,dynamic field mapping>> is enabled where the
+`dynamic` parameter is set to `runtime`, new fields are automatically added to
+the index mapping as runtime fields.
+
 Runtime fields are similar to the <<script-fields,`script_fields`>> parameter
 of the `_search` request, but also make the script results available anywhere
 in a search request.