Re-enable doc value skippers on host.name (elastic#138310)

This PR removes the feature flag from the check to enable doc value skippers on host.name.

This PR is a follow-up to elastic#138252 to bring the fixes into main.

Author: jordan-powers

server/src/main/java/org/elasticsearch/index/mapper/KeywordFieldMapper.java

@@ -462,7 +462,7 @@ private boolean shouldUseTimeSeriesSkipper() {
 
         private boolean shouldUseHostnameSkipper(final String fullFieldName) {
             return hasDocValues.get()
-                && indexSettings.useDocValuesSkipper()
+                && IndexSettings.USE_DOC_VALUES_SKIPPER.get(indexSettings.getSettings())
                 && indexSettings.getIndexVersionCreated().onOrAfter(IndexVersions.SKIPPERS_ENABLED_BY_DEFAULT)
                 && IndexMode.LOGSDB.equals(indexSettings.getMode())
                 && HOST_NAME.equals(fullFieldName)

server/src/test/java/org/elasticsearch/index/mapper/KeywordFieldMapperTests.java

@@ -968,12 +968,8 @@ public void testFieldTypeWithSkipDocValues_LogsDbMode() throws IOException {
         }));
 
         final KeywordFieldMapper mapper = (KeywordFieldMapper) mapperService.documentMapper().mappers().getMapper("host.name");
-        if (mapperService.getIndexSettings().useDocValuesSkipper()) {
-            assertTrue(mapper.fieldType().indexType().hasDocValuesSkipper());
-        } else {
-            assertFalse(mapper.fieldType().indexType().hasDocValuesSkipper());
-            assertTrue(mapper.fieldType().indexType().hasTerms());
-        }
+        assertTrue(mapper.fieldType().indexType().hasDocValuesSkipper());
+        assertFalse(mapper.fieldType().indexType().hasTerms());
     }
 
     public void testFieldTypeDefault_StandardMode() throws IOException {
@@ -1024,12 +1020,8 @@ public void testFieldTypeDefault_ConfiguredIndexedWithSettingOverride() throws I
 
         final KeywordFieldMapper mapper = (KeywordFieldMapper) mapperService.documentMapper().mappers().getMapper("host.name");
         assertTrue(mapper.fieldType().hasDocValues());
-        if (mapperService.getIndexSettings().useDocValuesSkipper()) {
-            assertTrue(mapper.fieldType().indexType().hasDocValuesSkipper());
-        } else {
-            assertFalse(mapper.fieldType().indexType().hasDocValuesSkipper());
-            assertTrue(mapper.fieldType().indexType().hasTerms());
-        }
+        assertTrue(mapper.fieldType().indexType().hasDocValuesSkipper());
+        assertFalse(mapper.fieldType().indexType().hasTerms());
     }
 
     public void testFieldTypeDefault_ConfiguredIndexedWithoutSettingOverride() throws IOException {
@@ -1046,12 +1038,8 @@ public void testFieldTypeDefault_ConfiguredIndexedWithoutSettingOverride() throw
 
         final KeywordFieldMapper mapper = (KeywordFieldMapper) mapperService.documentMapper().mappers().getMapper("host.name");
         assertTrue(mapper.fieldType().hasDocValues());
-        if (mapperService.getIndexSettings().useDocValuesSkipper()) {
-            assertTrue(mapper.fieldType().indexType().hasDocValuesSkipper());
-        } else {
-            assertFalse(mapper.fieldType().indexType().hasDocValuesSkipper());
-            assertTrue(mapper.fieldType().indexType().hasTerms());
-        }
+        assertTrue(mapper.fieldType().indexType().hasDocValuesSkipper());
+        assertFalse(mapper.fieldType().indexType().hasTerms());
     }
 
     public void testFieldTypeDefault_ConfiguredDocValues() throws IOException {
@@ -1068,12 +1056,8 @@ public void testFieldTypeDefault_ConfiguredDocValues() throws IOException {
 
         final KeywordFieldMapper mapper = (KeywordFieldMapper) mapperService.documentMapper().mappers().getMapper("host.name");
         assertTrue(mapper.fieldType().hasDocValues());
-        if (mapperService.getIndexSettings().useDocValuesSkipper()) {
-            assertTrue(mapper.fieldType().indexType().hasDocValuesSkipper());
-        } else {
-            assertFalse(mapper.fieldType().indexType().hasDocValuesSkipper());
-            assertTrue(mapper.fieldType().indexType().hasTerms());
-        }
+        assertTrue(mapper.fieldType().indexType().hasDocValuesSkipper());
+        assertFalse(mapper.fieldType().indexType().hasTerms());
     }
 
     public void testFieldTypeDefault_LogsDbMode_NonSortField() throws IOException {
@@ -1108,12 +1092,8 @@ public void testFieldTypeWithSkipDocValues_IndexedFalseDocValuesTrue() throws IO
 
         final KeywordFieldMapper mapper = (KeywordFieldMapper) mapperService.documentMapper().mappers().getMapper("host.name");
         assertTrue(mapper.fieldType().hasDocValues());
-        if (mapperService.getIndexSettings().useDocValuesSkipper()) {
-            assertTrue(mapper.fieldType().indexType().hasDocValuesSkipper());
-        } else {
-            assertFalse(mapper.fieldType().indexType().hasDocValuesSkipper());
-            assertTrue(mapper.fieldType().indexType().hasOnlyDocValues());
-        }
+        assertTrue(mapper.fieldType().indexType().hasDocValuesSkipper());
+        assertFalse(mapper.fieldType().indexType().hasTerms());
     }
 
     public void testFieldTypeDefault_IndexedFalseDocValuesFalse() throws IOException {