Correct how meta-field is defined for pre 7.8 hits (#57951)

We keep a static list of meta-fields: META_FIELDS_BEFORE_7_8
as it was before.
This is done to ensure the backwards compatability with pre 7.8 nodes.

Closes #57831

rest-api-spec/src/main/resources/rest-api-spec/test/search.inner_hits/10_basic.yml

@@ -44,8 +44,8 @@ setup:
 "Nested doc version and seqIDs":
 
     - skip:
-        version: "all" #" - 6.99.99"
-        reason:  "AwaitsFix https://github.com/elastic/elasticsearch/issues/57831"#"Triggers warnings before 7.0"
+        version: " - 6.99.99"
+        reason:  "Triggers warnings before 7.0"
 
     - do:
         index:

server/src/main/java/org/elasticsearch/index/get/GetResult.java

@@ -99,7 +99,7 @@ public GetResult(StreamInput in) throws IOException {
                 documentFields = new HashMap<>();
                 metaFields = new HashMap<>();
                 fields.forEach((fieldName, docField) ->
-                    (MapperService.isMetadataFieldStatic(fieldName) ? metaFields : documentFields).put(fieldName, docField));
+                    (MapperService.META_FIELDS_BEFORE_7DOT8.contains(fieldName) ? metaFields : documentFields).put(fieldName, docField));
             }
         } else {
             metaFields = Collections.emptyMap();

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

@@ -55,14 +55,14 @@
 import org.elasticsearch.index.mapper.Mapper.BuilderContext;
 import org.elasticsearch.index.query.QueryShardContext;
 import org.elasticsearch.index.similarity.SimilarityService;
-import org.elasticsearch.indices.IndicesModule;
 import org.elasticsearch.indices.InvalidTypeNameException;
 import org.elasticsearch.indices.mapper.MapperRegistry;
 import org.elasticsearch.search.suggest.completion.context.ContextMapping;
 
 import java.io.Closeable;
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
@@ -119,6 +119,11 @@ public enum MergeReason {
     public static final Setting<Boolean> INDEX_MAPPER_DYNAMIC_SETTING =
         Setting.boolSetting("index.mapper.dynamic", INDEX_MAPPER_DYNAMIC_DEFAULT,
             Property.Dynamic, Property.IndexScope, Property.Deprecated);
+    // Deprecated set of meta-fields, for checking if a field is meta, use an instance method isMetadataField instead
+    @Deprecated
+    public static final Set<String> META_FIELDS_BEFORE_7DOT8 =
+        Collections.unmodifiableSet(new HashSet<>(Arrays.asList(
+        "_id", IgnoredFieldMapper.NAME, "_index", "_routing", "_size", "_timestamp", "_ttl", "_type")));
 
     private static final DeprecationLogger deprecationLogger = new DeprecationLogger(LogManager.getLogger(MapperService.class));
     static final String DEFAULT_MAPPING_ERROR_MESSAGE = "[_default_] mappings are not allowed on new indices and should no " +
@@ -804,22 +809,6 @@ public void close() throws IOException {
         indexAnalyzers.close();
     }
 
-    /**
-     * @return Whether a field is a metadata field
-     * Deserialization of SearchHit objects sent from pre 7.8 nodes and GetResults objects sent from pre 7.3 nodes,
-     * uses this method to divide fields into meta and document fields.
-     * TODO: remove in v 9.0
-     * @deprecated  Use an instance method isMetadataField instead
-     */
-    @Deprecated
-    public static boolean isMetadataFieldStatic(String fieldName) {
-        if (IndicesModule.getBuiltInMetadataFields().contains(fieldName)) {
-            return true;
-        }
-        // if a node had Size Plugin installed, _size field should also be considered a meta-field
-        return fieldName.equals("_size");
-    }
-
     /**
      * @return Whether a field is a metadata field.
      * this method considers all mapper plugins

server/src/main/java/org/elasticsearch/search/SearchHit.java

@@ -168,7 +168,7 @@ public SearchHit(StreamInput in) throws IOException {
             documentFields = new HashMap<>();
             metaFields = new HashMap<>();
             fields.forEach((fieldName, docField) ->
-                (MapperService.isMetadataFieldStatic(fieldName) ? metaFields : documentFields).put(fieldName, docField));
+                (MapperService.META_FIELDS_BEFORE_7DOT8.contains(fieldName) ? metaFields : documentFields).put(fieldName, docField));
         }
 
         int size = in.readVInt();

server/src/test/java/org/elasticsearch/search/SearchHitsTests.java

@@ -22,11 +22,9 @@
 import org.apache.lucene.search.SortField;
 import org.apache.lucene.search.TotalHits;
 import org.apache.lucene.util.TestUtil;
-import org.elasticsearch.Version;
 import org.elasticsearch.action.OriginalIndices;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.bytes.BytesReference;
-import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.Writeable;
 import org.elasticsearch.common.lucene.LuceneTests;
 import org.elasticsearch.common.text.Text;
@@ -39,10 +37,8 @@
 import org.elasticsearch.index.Index;
 import org.elasticsearch.index.shard.ShardId;
 import org.elasticsearch.test.AbstractSerializingTestCase;
-import org.elasticsearch.test.VersionUtils;
 
 import java.io.IOException;
-import java.util.Base64;
 import java.util.Collections;
 import java.util.function.Predicate;
 
@@ -271,37 +267,4 @@ public void testFromXContentWithShards() throws IOException {
 
         }
     }
-
-    public void testReadFromPre6_6_0() throws IOException {
-        try (StreamInput in = StreamInput.wrap(Base64.getDecoder().decode("AQC/gAAAAAA="))) {
-            in.setVersion(VersionUtils.randomVersionBetween(random(), Version.V_6_0_0, VersionUtils.getPreviousVersion(Version.V_6_6_0)));
-            SearchHits searchHits = new SearchHits(in);
-            assertEquals(0, searchHits.getHits().length);
-            assertNotNull(searchHits.getTotalHits());
-            assertEquals(0L, searchHits.getTotalHits().value);
-            assertEquals(TotalHits.Relation.EQUAL_TO, searchHits.getTotalHits().relation);
-            assertEquals(-1F, searchHits.getMaxScore(), 0F);
-            assertNull(searchHits.getSortFields());
-            assertNull(searchHits.getCollapseField());
-            assertNull(searchHits.getCollapseValues());
-        }
-    }
-
-    public void testSerializationPre6_6_0() throws IOException {
-        Version version = VersionUtils.randomVersionBetween(random(), Version.V_6_0_0, VersionUtils.getPreviousVersion(Version.V_6_6_0));
-        SearchHits original = createTestItem(randomFrom(XContentType.values()), false, true, TotalHits.Relation.EQUAL_TO);
-        SearchHits deserialized = copyInstance(original, version);
-        assertArrayEquals(original.getHits(), deserialized.getHits());
-        assertEquals(original.getMaxScore(), deserialized.getMaxScore(), 0F);
-        if (original.getTotalHits() == null) {
-            assertNull(deserialized.getTotalHits());
-        } else {
-            assertNotNull(deserialized.getTotalHits());
-            assertEquals(original.getTotalHits().value, deserialized.getTotalHits().value);
-            assertEquals(original.getTotalHits().relation, deserialized.getTotalHits().relation);
-        }
-        assertNull(deserialized.getSortFields());
-        assertNull(deserialized.getCollapseField());
-        assertNull(deserialized.getCollapseValues());
-    }
 }

server/src/test/java/org/elasticsearch/search/SearchSortValuesTests.java

@@ -20,9 +20,7 @@
 package org.elasticsearch.search;
 
 import org.apache.lucene.util.BytesRef;
-import org.elasticsearch.Version;
 import org.elasticsearch.common.Strings;
-import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.Writeable;
 import org.elasticsearch.common.lucene.LuceneTests;
 import org.elasticsearch.common.xcontent.ToXContent;
@@ -32,11 +30,9 @@
 import org.elasticsearch.common.xcontent.json.JsonXContent;
 import org.elasticsearch.test.AbstractSerializingTestCase;
 import org.elasticsearch.test.RandomObjects;
-import org.elasticsearch.test.VersionUtils;
 
 import java.io.IOException;
 import java.util.Arrays;
-import java.util.Base64;
 
 public class SearchSortValuesTests extends AbstractSerializingTestCase<SearchSortValues> {
 
@@ -140,22 +136,4 @@ protected SearchSortValues mutateInstance(SearchSortValues instance) {
         values[sortValues.length] = randomSortValue(randomFrom(XContentType.values()), randomBoolean());
         return new SearchSortValues(values);
     }
-
-    public void testSerializationPre6_6_0() throws IOException {
-        Version version = VersionUtils.randomVersionBetween(random(), Version.V_6_0_0, VersionUtils.getPreviousVersion(Version.V_6_6_0));
-        SearchSortValues original = createTestInstance();
-        SearchSortValues deserialized = copyInstance(original, version);
-        assertArrayEquals(original.getFormattedSortValues(), deserialized.getFormattedSortValues());
-        assertEquals(0, deserialized.getRawSortValues().length);
-    }
-
-    public void testReadFromPre6_6_0() throws IOException {
-        try (StreamInput in = StreamInput.wrap(Base64.getDecoder().decode("AwIAAAABAQEyBUAIAAAAAAAAAAAAAAAA"))) {
-            in.setVersion(VersionUtils.randomVersionBetween(random(), Version.V_6_0_0, VersionUtils.getPreviousVersion(Version.V_6_6_0)));
-            SearchSortValues deserialized = new SearchSortValues(in);
-            SearchSortValues expected = new SearchSortValues(new Object[]{1, "2", 3d});
-            assertEquals(expected, deserialized);
-            assertEquals(0, deserialized.getRawSortValues().length);
-        }
-    }
 }