Add filtering to fieldcaps endpoint

docs/changelog/83636.yaml

@@ -0,0 +1,6 @@
+pr: 83636
+summary: Add filtering to fieldcaps endpoint
+area: Search
+type: enhancement
+issues:
+ - 82966

docs/reference/search/field-caps.asciidoc

@@ -77,6 +77,15 @@ include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=index-ignore-unavailab
   (Optional, Boolean) If `true`, unmapped fields are included in the response.
   Defaults to `false`.
 
+`filters`::
+(Optional, string) Comma-separated list of filters to apply to the response.  The
+following filters are supported: +metadata,-metadata,-parent,-nested,-multifield
+
+`types`::
+(Optional, string) Comma-separated list of field types to include. Any fields that
+do not match one of these types will be excluded from the results.  Defaults to empty,
+meaning that all field types are returned.
+
 [[search-field-caps-api-request-body]]
 ==== {api-request-body-title}
 

rest-api-spec/src/main/resources/rest-api-spec/api/field_caps.json

@@ -63,6 +63,14 @@
         "type":"boolean",
         "default":false,
         "description":"Indicates whether unmapped fields should be included in the response."
+      },
+      "filters": {
+        "type":"list",
+        "description":"An optional set of filters: can include +metadata,-metadata,-nested,-multifield,-parent"
+      },
+      "types": {
+        "type": "list",
+        "description":"Only return results for fields that have one of the types in the list"
       }
     },
     "body":{

rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/field_caps/50_fieldtype_filter.yml

@@ -0,0 +1,213 @@
+---
+setup:
+  - skip:
+      version: "- 8.1.99"
+      reason: Field type filters were added in 8.2
+  - do:
+      indices.create:
+        index: test1
+        body:
+          mappings:
+            properties:
+              text:
+                type:     text
+                fields:
+                  keyword:
+                    type: keyword
+              keyword:
+                type:     keyword
+              number:
+                type:     double
+              geo:
+                type:     geo_point
+              misc:
+                type:     text
+              object:
+                type: object
+                properties:
+                  nested1 :
+                    type : text
+                    index: false
+                  nested2:
+                    type: float
+                    doc_values: false
+              level1:
+                type: nested
+                properties:
+                  level2:
+                    type: object
+                    properties:
+                      leaf1:
+                        type: text
+                        index: false
+            runtime:
+              misc.keyword:
+                type: keyword
+
+  - do:
+      indices.create:
+        index: test2
+        body:
+          mappings:
+            properties:
+              text:
+                type:     text
+              keyword:
+                type:     keyword
+              number:
+                type:     double
+              date:
+                type:     date
+              geo:
+                type:     geo_point
+              object:
+                type: object
+                properties:
+                  nested1 :
+                    type : text
+                    index: true
+                  nested2:
+                    type: float
+                    doc_values: true
+              level1:
+                type: nested
+                properties:
+                  level2:
+                    type: object
+                    properties:
+                      leaf1:
+                        type: text
+                        index: false
+  - do:
+      indices.create:
+        index: test3
+        body:
+          mappings:
+            properties:
+              text:
+                type:     text
+              keyword:
+                type:     keyword
+              number:
+                type:     long
+              date:
+                type:     date
+              non_indexed_date:
+                type:     date
+                index:    false
+              non_indexed_keyword:
+                type:     keyword
+                index:    false
+              non_indexed_boolean:
+                type:     boolean
+                index:    false
+              non_indexed_ip:
+                type:     ip
+                index:    false
+              non_indexed_geo_point:
+                type:     geo_point
+                index:    false
+              geo:
+                type:     keyword
+              object:
+                type: nested
+                properties:
+                  nested1 :
+                    type : long
+                    index: false
+                  nested2:
+                    type: keyword
+                    doc_values: false
+---
+"No filters includes all the following fields":
+  - do:
+      field_caps:
+        index: 'test1,test2,test3'
+        fields: '*'
+
+  - is_true: fields.object
+  - is_true: fields.text
+  - is_true: fields.text\\.keyword
+  - is_true: fields._seq_no
+  - is_true: fields.level1\\.level2\\.leaf1
+  - is_true: fields.level1
+
+---
+"Exclude parent objects":
+  - do:
+      field_caps:
+        index: 'test1,test2,test3'
+        fields: '*'
+        filters: '-parent'
+
+  - is_true: fields.object\\.nested1
+  - is_false: fields.object
+
+---
+"Exclude metadata fields":
+  - do:
+      field_caps:
+        index: 'test1,test2,test3'
+        fields: '*'
+        filters: '-metadata'
+
+  - is_false: fields._seq_no
+
+---
+"Exclude non-metadata fields":
+  - do:
+      field_caps:
+        index: 'test1,test2,test3'
+        fields: '*'
+        filters: '+metadata'
+
+  - is_true: fields._seq_no
+  - is_false: fields.text
+
+---
+"Exclude nested fields":
+  - do:
+      field_caps:
+        index: 'test1,test2,test3'
+        fields: '*'
+        filters: '-nested'
+
+  - is_false: fields.level1
+  - is_false: fields.level1\\.level2\\.leaf1
+
+---
+"Exclude multifields":
+  - do:
+      field_caps:
+        index: 'test1,test2,test3'
+        fields: '*'
+        filters: '-multifield'
+
+  - is_false: fields.text\\.keyword
+  - is_true: fields.misc\\.keyword
+
+---
+"Field type filters":
+  - do:
+      field_caps:
+        index: 'test1,test2,test3'
+        fields: '*'
+        types: 'text,keyword,long'
+
+  - is_false: fields.date
+  - is_false: fields.non_indexed_boolean
+  - is_true: fields.non_indexed_keyword
+  - is_true: fields.misc
+
+---
+"Field type filters with field name restrictions":
+  - do:
+      field_caps:
+        index: 'test1,test2,test3'
+        fields: 'non_*,text'
+        types: 'text,keyword,long'
+
+  - is_false: fields.non_indexed_boolean
+  - is_true: fields.non_indexed_keyword
+  - is_false: fields.misc
+  - is_true: fields.text