Allow specify dynamic templates in bulk request (#69948)

This change allows users to specify dynamic templates in a bulk request.

```
PUT myindex
{
  "mappings": {
    "dynamic_templates": [{
      "time_histograms": {
        "mapping": {
          "type": "histogram",
          "meta": {
            "unit": "s"
          }
        }
      }
    }]
  }
}
```

```
POST myindex/_bulk
{ "index": { "dynamic_templates": { "response_times": "time_histograms" } } }
{ "@timestamp": "2020-08-12", "response_times": { "values": [1, 10], "counts": [5, 1] }}
```

Closes #61939

docs/reference/docs/bulk.asciidoc

@@ -283,6 +283,8 @@ include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=bulk-index]
 include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=bulk-id]
 
 include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=bulk-require-alias]
+
+include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=bulk-dynamic-templates]
 --
 
 `delete`::
@@ -311,6 +313,8 @@ include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=bulk-index]
 include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=bulk-id]
 
 include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=bulk-require-alias]
+
+include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=bulk-dynamic-templates]
 --
 
 `update`::
@@ -738,3 +742,39 @@ The API returns the following result.
 }
 ----
 // TESTRESPONSE[s/"index_uuid": "aAsFqTI0Tc2W0LCWgPNrOA"/"index_uuid": $body.$_path/]
+
+
+[discrete]
+[[bulk-dynamic-templates]]
+===== Example with dynamic templates parameter
+
+The below example creates a dynamic template, then performs a bulk request
+consisting of index/create requests with the `dynamic_templates` parameter.
+
+[source,console]
+----
+PUT my-index/
+{
+  "mappings": {
+    "dynamic_templates": [
+      {
+        "geo_point": {
+             "mapping": {
+                "type" : "geo_point"
+             }
+        }
+      }
+    ]
+  }
+}
+
+POST /_bulk
+{ "index" : { "_index" : "my_index", "_id" : "1", "dynamic_templates": {"work_location": "geo_point"}} }
+{ "field" : "value1", "work_location": "41.12,-71.34", "raw_location": "41.12,-71.34"}
+{ "create" : { "_index" : "my_index", "_id" : "2", "dynamic_templates": {"home_location": "geo_point"}} }
+{ "field" : "value2", "home_location": "41.12,-71.34"}
+----
+
+The bulk request creates two new fields `work_location` and `home_location` with type `geo_point` according
+to the `dynamic_templates` parameter; however, the `raw_location` field is created using default dynamic mapping
+rules, as a `text` field in that case since it is supplied as a string in the JSON document.

docs/reference/mapping/dynamic/templates.asciidoc

@@ -14,6 +14,10 @@ name
 * <<path-match-unmatch,`path_match` and `path_unmatch`>> operate on the full
 dotted path to the field
 
+* if a dynamic template does not define `match_mapping_type` nor `match` nor
+`path_match`, then it won't match any field, but it can be referred to by
+name in `dynamic_templates` as part of a <bulk, bulk request>.
+
 Use the `{name}` and `{dynamic_type}` <<template-variables,template variables>>
 in the mapping specification as placeholders.
 

docs/reference/rest-api/common-parms.asciidoc

@@ -626,6 +626,15 @@ If `true`, the destination must be an <<indices-aliases,index alias>>. Defaults
 `false`.
 end::require-alias[]
 
+tag::bulk-dynamic-templates[]
+`dynamic_templates`::
+(Optional, map)
+A map from the full name of fields to the name of <<dynamic-templates, dynamic templates>.
+Defaults to an empty map. If a name matches a dynamic template, then that template will be 
+applied regardless of other match predicates defined in the template. And if a field is 
+already defined in the mapping, then this parameter won't be used.
+end::bulk-dynamic-templates[]
+
 tag::node-filter[]
 `<node_filter>`::
 (Optional, string)

rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/bulk/11_dynamic_templates.yml

@@ -0,0 +1,171 @@
+---
+"Dynamic templates":
+  - skip:
+      version: " - 7.99.99"
+      reason: "Dynamic templates parameter is added to bulk requests in 8.0"
+
+  - do:
+      indices.create:
+        index: test_index
+        body:
+          mappings:
+            dynamic_templates:
+              - location:
+                  mapping:
+                    type: geo_point
+              - my_location:
+                  match: my*
+                  mapping:
+                    type: geo_point
+              - string:
+                  mapping:
+                    type: keyword
+  - do:
+      bulk:
+        refresh: true
+        body:
+          - index:
+              _index: test_index
+              _id: id_1
+              dynamic_templates:
+                location: location
+          - { "location": [ -71.34, 41.12 ]}
+          - index:
+              _index: test_index
+              _id: id_2
+              dynamic_templates:
+                location: location
+          - { "location": "41.12,-71.34"}
+  - match: { errors: false }
+  - match: { items.0.index.result: created }
+  - match: { items.1.index.result: created }
+
+  - do:
+      search:
+        index: test_index
+        body:
+          query:
+            geo_bounding_box:
+              location:
+                top_left:
+                  lat: 42
+                  lon: -72
+                bottom_right:
+                  lat: 40
+                  lon: -74
+  - match: { hits.total.value: 2 }
+  - match: { hits.hits.0._id: id_1 }
+  - match: { hits.hits.1._id: id_2 }
+
+  - do:
+      bulk:
+        refresh: true
+        body:
+          - index:
+              _index: test_index
+              _id: id_3
+          - { "my_location": "41.12,-71.34" } # matches the field name defined in the `my_location` template
+          - index:
+              _index: test_index
+              _id: id_4
+              dynamic_templates:
+                my_location: my_location
+          - { "my_location": "41.12,-71.34" } # use dynamic_templates parameter
+  - do:
+      search:
+        index: test_index
+        body:
+          query:
+            geo_bounding_box:
+              my_location:
+                top_left:
+                  lat: 42
+                  lon: -72
+                bottom_right:
+                  lat: 40
+                  lon: -74
+  - match: { hits.total.value: 2 }
+  - match: { hits.hits.0._id: id_3 }
+  - match: { hits.hits.1._id: id_4 }
+
+  - do:
+      bulk:
+        refresh: true
+        body:
+          - index:
+              _index: test_index
+              _id: id_5
+              dynamic_templates:
+                location: foo_bar  # ok as fields are defined
+          - { "location": [ -71.34, 41.12 ]}
+          - index:
+              _index: test_index
+              _id: id_6
+              dynamic_templates:
+                my_location: foo_bar # ok as fields are defined
+          - { "my_location": "41.12,-71.34" }
+          - index:
+              _index: test_index
+              _id: id_7
+              dynamic_templates:
+                location: bar_foo # ok as fields are defined
+          - { "location": "41.12,-71.34" }
+  - match: { errors: false }
+  - match: { items.0.index.result: created }
+  - match: { items.1.index.result: created }
+  - match: { items.2.index.result: created }
+
+  - do:
+      bulk:
+        refresh: true
+        body:
+          - index:
+              _index: test_index
+              _id: id_8
+              dynamic_templates:
+                foo_location: bar_foo
+          - { "foo_location": [ -71.34, 41.12 ] } # failed because dynamic template is not found
+          - index:
+              _index: test_index
+              _id: id_9
+              dynamic_templates:
+                foo_location: foo_bar
+          - { "foo_location": "41.12,-71.34" } # failed because dynamic template is not found
+          - index:
+              _index: test_index
+              _id: id_10
+              dynamic_templates:
+                new_location: foo
+          - { "location": "41.12,-71.34"} # ok as fields are defined
+  - match: { errors: true }
+  - match: { items.0.index.status: 400 }
+  - match: { items.0.index.error.type: mapper_parsing_exception }
+  - match: { items.0.index.error.reason: "Can't find dynamic template for dynamic template name [bar_foo] of field [foo_location]"}
+  - match: { items.1.index.status: 400 }
+  - match: { items.1.index.error.type: mapper_parsing_exception }
+  - match: { items.1.index.error.reason: "Can't find dynamic template for dynamic template name [foo_bar] of field [foo_location]"}
+  - match: { items.2.index.status: 201 }
+  - match: { items.2.index.result: created }
+
+  # Dynamic template has a wrong type
+  - do:
+      bulk:
+        body:
+          - index:
+              _index: test_index
+              _id: id_11
+              dynamic_templates:
+                foo: string
+          - { "foo.bar": "hello world" } # failed because dynamic template has a wrong type
+          - index:
+              _index: test_index
+              _id: id_12
+              dynamic_templates:
+                foo.bar: string
+          - { "foo.bar": "hello world" } # ok
+  - match: { errors: true }
+  - match: { items.0.index.status: 400 }
+  - match: { items.0.index.error.type: mapper_parsing_exception }
+  - match: { items.0.index.error.reason: "Field [foo] must be an object; but it's configured as [keyword] in dynamic template [string]"}
+  - match: { items.1.index.status: 201 }
+  - match: { items.1.index.result: created }