Make FieldNamesFieldMapper responsible for adding its own doc fields (#71929)

The FieldNamesFieldMapper is a metadata mapper defining a field that
can be used for exists queries if a mapper does not use doc values or
norms. Currently, data is added to it via a special method on FieldMapper
that pulls the metadata mapper from a mapping lookup, checks to see
if it is enabled, and then adds the relevant value to a lucene document.

This is one of only two places that pulls a metadata mapper from the
MappingLookup, and it would be nice to remove this method. This commit
refactors field name handling by instead storing the names of fields to
index in the fieldnames field in a set on the ParseContext, and then
building the field itself in FieldNamesFieldMapper.postParse(). This means
that all of the responsibility for enabling indexing, etc, is handled within
the metadata mapper itself.

Author: romseygeek

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

@@ -331,7 +331,7 @@ protected void parseCreateField(ParseContext context) throws IOException {
 
         Field field = new Field(fieldType().name(), value, fieldType);
         context.doc().add(field);
-        createFieldNamesField(context);
+        context.addToFieldNames(fieldType().name());
     }
 
     @Override

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

@@ -379,7 +379,7 @@ protected void parseCreateField(ParseContext context) throws IOException {
         context.doc().addAll(fields);
 
         if (hasDocValues == false && (indexed || stored)) {
-            createFieldNamesField(context);
+            context.addToFieldNames(fieldType().name());
         }
     }
 

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

@@ -588,7 +588,7 @@ protected void parseCreateField(ParseContext context) throws IOException {
             context.doc().add(new Field(prefixField.fieldType().name(), value, prefixField.getLuceneFieldType()));
         }
         if (fieldType().fieldType.omitNorms()) {
-            createFieldNamesField(context);
+            context.addToFieldNames(fieldType().name());
         }
     }
 

modules/percolator/src/main/java/org/elasticsearch/percolator/PercolatorFieldMapper.java

@@ -433,7 +433,7 @@ void processQuery(Query query, ParseContext context) {
             doc.add(new Field(extractionResultField.name(), EXTRACTION_PARTIAL, INDEXED_KEYWORD));
         }
 
-        createFieldNamesField(context);
+        context.addToFieldNames(fieldType().name());
         if (indexVersionCreated.onOrAfter(Version.V_6_1_0)) {
             doc.add(new NumericDocValuesField(minimumShouldMatchFieldMapper.name(), result.minimumShouldMatch));
         }

modules/percolator/src/test/java/org/elasticsearch/percolator/PercolatorFieldMapperTests.java

@@ -287,7 +287,7 @@ public void testExtractTermsAndRanges_partial() throws Exception {
         ParseContext.Document document = parseContext.doc();
 
         PercolatorFieldMapper.PercolatorFieldType fieldType = (PercolatorFieldMapper.PercolatorFieldType) fieldMapper.fieldType();
-        assertThat(document.getFields().size(), equalTo(4));
+        assertThat(document.getFields().size(), equalTo(3));
         assertThat(document.getFields().get(0).binaryValue().utf8ToString(), equalTo("field\u0000term"));
         assertThat(document.getField(fieldType.extractionResultField.name()).stringValue(), equalTo(EXTRACTION_PARTIAL));
     }

plugins/analysis-icu/src/main/java/org/elasticsearch/index/mapper/ICUCollationKeywordFieldMapper.java

@@ -464,7 +464,7 @@ protected void parseCreateField(ParseContext context) throws IOException {
         if (hasDocValues) {
             context.doc().add(new SortedSetDocValuesField(fieldType().name(), binaryValue));
         } else if (fieldType.indexOptions() != IndexOptions.NONE || fieldType.stored()) {
-            createFieldNamesField(context);
+            context.addToFieldNames(fieldType().name());
         }
     }
 

plugins/mapper-annotated-text/src/main/java/org/elasticsearch/index/mapper/annotatedtext/AnnotatedTextFieldMapper.java

@@ -539,7 +539,7 @@ protected void parseCreateField(ParseContext context) throws IOException {
             Field field = new Field(mappedFieldType.name(), value, fieldType);
             context.doc().add(field);
             if (fieldType.omitNorms()) {
-                createFieldNamesField(context);
+                context.addToFieldNames(fieldType().name());
             }
         }
     }

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

@@ -173,7 +173,7 @@ public void indexValue(ParseContext context, byte[] value) {
             // Only add an entry to the field names field if the field is stored
             // but has no doc values so exists query will work on a field with
             // no doc values
-            createFieldNamesField(context);
+            context.addToFieldNames(fieldType().name());
         }
     }
 

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

@@ -295,7 +295,7 @@ private void indexValue(ParseContext context, Boolean value) {
         if (hasDocValues) {
             context.doc().add(new SortedNumericDocValuesField(fieldType().name(), value ? 1 : 0));
         } else {
-            createFieldNamesField(context);
+            context.addToFieldNames(fieldType().name());
         }
     }
 

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

@@ -372,7 +372,7 @@ public void parse(ParseContext context) throws IOException {
             }
         }
 
-        createFieldNamesField(context);
+        context.addToFieldNames(fieldType().name());
         for (CompletionInputMetadata metadata: inputMap.values()) {
             ParseContext externalValueContext = context.createExternalValueContext(metadata);
             multiFields.parse(this, externalValueContext);