Implement fields fetch for runtime fields (backport of #61995) (#62416)

This implements the `fields` API in `_search` for runtime fields using
doc values. Most of that implementation is stolen from the
`docvalue_fields` fetch sub-phase, just moved into the same API that the
`fields` API uses. At this point the `docvalue_fields` fetch phase looks
like a special case of the `fields` API.

While I was at it I moved the "which doc values sub-implementation
should I use for fetching?" question from a bunch of `instanceof`s to a
method on `LeafFieldData` so we can be much more flexible with what is
returned and we're not forced to extend certain classes just to make the
fetch phase happy.

Relates to #59332

Author: nik9000

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

@@ -183,7 +183,7 @@ private Float objectToFloat(Object value) {
     }
 
     @Override
-    public ValueFetcher valueFetcher(MapperService mapperService, String format) {
+    public ValueFetcher valueFetcher(MapperService mapperService, SearchLookup searchLookup, String format) {
         if (format != null) {
             throw new IllegalArgumentException("Field [" + name() + "] of type [" + typeName() + "] doesn't support formats.");
         }

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

@@ -162,7 +162,7 @@ protected void parseCreateField(ParseContext context) throws IOException {
     }
 
     @Override
-    public ValueFetcher valueFetcher(MapperService mapperService, String format) {
+    public ValueFetcher valueFetcher(MapperService mapperService, SearchLookup searchLookup, String format) {
         if (format != null) {
             throw new IllegalArgumentException("Field [" + name() + "] of type [" + typeName() + "] doesn't support formats.");
         }

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

@@ -398,7 +398,7 @@ private static double objectToDouble(Object value) {
     }
 
     @Override
-    public ValueFetcher valueFetcher(MapperService mapperService, String format) {
+    public ValueFetcher valueFetcher(MapperService mapperService, SearchLookup searchLookup, String format) {
         if (format != null) {
             throw new IllegalArgumentException("Field [" + name() + "] of type [" + typeName() + "] doesn't support formats.");
         }
@@ -545,5 +545,25 @@ public int docValueCount() {
             }
         }
 
+        @Override
+        public DocValueFetcher.Leaf getLeafValueFetcher(DocValueFormat format) {
+            SortedNumericDoubleValues values = getDoubleValues();
+            return new DocValueFetcher.Leaf() {
+                @Override
+                public boolean advanceExact(int docId) throws IOException {
+                    return values.advanceExact(docId);
+                }
+
+                @Override
+                public int docValueCount() throws IOException {
+                    return values.docValueCount();
+                }
+
+                @Override
+                public Object nextValue() throws IOException {
+                    return format.format(values.nextValue());
+                }
+            };
+        }
     }
 }

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

@@ -54,6 +54,7 @@
 import org.elasticsearch.index.query.QueryShardContext;
 import org.elasticsearch.index.similarity.SimilarityProvider;
 import org.elasticsearch.index.similarity.SimilarityService;
+import org.elasticsearch.search.lookup.SearchLookup;
 
 import java.io.IOException;
 import java.util.ArrayList;
@@ -419,7 +420,7 @@ protected void parseCreateField(ParseContext context) {
         }
 
         @Override
-        public ValueFetcher valueFetcher(MapperService mapperService, String format) {
+        public ValueFetcher valueFetcher(MapperService mapperService, SearchLookup searchLookup, String format) {
             throw new UnsupportedOperationException();
         }
 
@@ -465,7 +466,7 @@ protected void mergeOptions(FieldMapper other, List<String> conflicts) {
         }
 
         @Override
-        public ValueFetcher valueFetcher(MapperService mapperService, String format) {
+        public ValueFetcher valueFetcher(MapperService mapperService, SearchLookup searchLookup, String format) {
             throw new UnsupportedOperationException();
         }
 
@@ -588,7 +589,7 @@ protected void parseCreateField(ParseContext context) throws IOException {
     }
 
     @Override
-    public ValueFetcher valueFetcher(MapperService mapperService, String format) {
+    public ValueFetcher valueFetcher(MapperService mapperService, SearchLookup searchLookup, String format) {
         throw new UnsupportedOperationException();
     }
 

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

@@ -25,6 +25,7 @@
 import org.apache.lucene.document.FieldType;
 import org.elasticsearch.common.xcontent.XContentBuilder;
 import org.elasticsearch.index.analysis.NamedAnalyzer;
+import org.elasticsearch.search.lookup.SearchLookup;
 
 import java.io.IOException;
 import java.util.Iterator;
@@ -159,7 +160,7 @@ protected void parseCreateField(ParseContext context) throws IOException {
     }
 
     @Override
-    public ValueFetcher valueFetcher(MapperService mapperService, String format) {
+    public ValueFetcher valueFetcher(MapperService mapperService, SearchLookup searchLookup, String format) {
         if (format != null) {
             throw new IllegalArgumentException("Field [" + name() + "] of type [" + typeName() + "] doesn't support formats.");
         }

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

@@ -147,7 +147,7 @@ public void testRejectMultiValuedFields() throws MapperParsingException, IOExcep
                 e.getCause().getMessage());
     }
 
-    public void testFetchSourceValue() {
+    public void testFetchSourceValue() throws IOException {
         Settings settings = Settings.builder().put(IndexMetadata.SETTING_VERSION_CREATED, Version.CURRENT.id).build();
         Mapper.BuilderContext context = new Mapper.BuilderContext(settings, new ContentPath());
         RankFeatureFieldMapper mapper = new RankFeatureFieldMapper.Builder("field").build(context);

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

@@ -260,7 +260,7 @@ public void testRejectIndexOptions() {
         assertWarnings("Parameter [index_options] has no effect on type [scaled_float] and will be removed in future");
     }
 
-    public void testFetchSourceValue() {
+    public void testFetchSourceValue() throws IOException {
         Settings settings = Settings.builder().put(IndexMetadata.SETTING_VERSION_CREATED, Version.CURRENT.id).build();
         Mapper.BuilderContext context = new Mapper.BuilderContext(settings, new ContentPath());
 

modules/mapper-extras/src/yamlRestTest/resources/rest-api-spec/test/scaled_float/10_basic.yml

@@ -122,3 +122,15 @@ setup:
   - match: { hits.total.value: 4 }
   - match: { hits.hits.0._id: "3" }
   - match: { hits.hits.0.sort.0: -2 }
+
+---
+"docvalue_fields":
+
+  - do:
+      search:
+        body:
+          docvalue_fields: [ "number" ]
+          sort:
+            number:
+              order: asc
+  - match: { hits.hits.0.fields.number: [-2.1] }

modules/parent-join/src/main/java/org/elasticsearch/join/mapper/MetaJoinFieldMapper.java

@@ -140,7 +140,7 @@ protected void parseCreateField(ParseContext context) throws IOException {
     }
 
     @Override
-    public ValueFetcher valueFetcher(MapperService mapperService, String format) {
+    public ValueFetcher valueFetcher(MapperService mapperService, SearchLookup searchLookup, String format) {
         throw new UnsupportedOperationException("Cannot fetch values for metadata field [" + typeName() + "].");
     }
 

modules/parent-join/src/main/java/org/elasticsearch/join/mapper/ParentIdFieldMapper.java

@@ -190,7 +190,7 @@ protected void parseCreateField(ParseContext context) throws IOException {
     }
 
     @Override
-    public ValueFetcher valueFetcher(MapperService mapperService, String format) {
+    public ValueFetcher valueFetcher(MapperService mapperService, SearchLookup searchLookup, String format) {
         throw new UnsupportedOperationException("Cannot fetch values for internal field [" + typeName() + "].");
     }