Mapped field types searchable with doc values (elastic#97724)

* Mapped field types searchable with doc values

When using TSDB, time series metrics aren't indexed but do have doc values.
Field caps should report those fields as searchable.

docs/changelog/97724.yaml

@@ -0,0 +1,5 @@
+pr: 97724
+summary: Mapped field types searchable with doc values
+area: TSDB
+type: bug
+issues: []

modules/mapper-extras/src/main/java/org/elasticsearch/index/mapper/extras/ScaledFloatFieldMapper.java

@@ -248,6 +248,11 @@ public boolean mayExistInIndex(SearchExecutionContext context) {
             return context.fieldExistsInIndex(name());
         }
 
+        @Override
+        public boolean isSearchable() {
+            return isIndexed() || hasDocValues();
+        }
+
         @Override
         public Query termQuery(Object value, SearchExecutionContext context) {
             failIfNotIndexedNorDocValuesFallback(context);

modules/mapper-extras/src/test/java/org/elasticsearch/index/mapper/extras/ScaledFloatFieldMapperTests.java

@@ -156,6 +156,25 @@ public void testNoDocValues() throws Exception {
         assertEquals(1230, pointField.numericValue().longValue());
     }
 
+    public void testDocValuesSearchable() throws Exception {
+        boolean[] indexables = new boolean[] { true, false };
+        boolean[] hasDocValues = new boolean[] { true, false };
+        for (boolean indexable : indexables) {
+            for (boolean hasDocValue : hasDocValues) {
+                MapperService mapperService = createMapperService(
+                    fieldMapping(
+                        b -> b.field("type", "scaled_float")
+                            .field("index", indexable)
+                            .field("doc_values", hasDocValue)
+                            .field("scaling_factor", 10.0)
+                    )
+                );
+                MappedFieldType fieldType = mapperService.fieldType("field");
+                assertEquals(fieldType.isSearchable(), indexable || hasDocValue);
+            }
+        }
+    }
+
     public void testStore() throws Exception {
         DocumentMapper mapper = createDocumentMapper(
             fieldMapping(b -> b.field("type", "scaled_float").field("store", true).field("scaling_factor", 10.0))

x-pack/plugin/src/yamlRestTest/resources/rest-api-spec/test/aggregate-metrics/90_tsdb_mappings.yml

@@ -83,3 +83,43 @@ aggregate_double_metric with wrong time series mappings:
                             metrics: [min, max, sum, value_count]
                             default_metric: max
                             time_series_metric: histogram
+
+---
+"Field caps with tsdb":
+  - skip:
+      version: " - 8.7.99"
+      reason: "Field caps fix in 8.9"
+
+  - do:
+      indices.create:
+        index: tsdb-fieldcap
+        body:
+          settings:
+            number_of_replicas: 0
+            mode: time_series
+            routing_path: [field1]
+            time_series:
+              start_time: "2000-01-01T00:00:00Z"
+              end_time: "2099-12-31T23:59:59Z"
+          mappings:
+            properties:
+              field1:
+                type: keyword
+                time_series_dimension: true
+              field2:
+                type: long
+                time_series_metric: gauge
+              field3:
+                type: scaled_float
+                scaling_factor: 100
+                time_series_metric: gauge
+
+  - do:
+      field_caps:
+        index: tsdb-fieldcap
+        fields: "field*"
+
+  - match: {indices: ["tsdb-fieldcap"]}
+  - match: {fields.field1.keyword.type: keyword}
+  - match: {fields.field3.scaled_float.type: scaled_float}
+  - match: {fields.field3.scaled_float.searchable: true}