Sort field tiebreaker for PIT (point in time) readers

modules/analysis-common/src/test/java/org/elasticsearch/analysis/common/DisableGraphQueryTests.java

@@ -85,7 +85,7 @@ public void setup() {
         indexService = createIndex("test", settings, "t",
             "text_shingle", "type=text,analyzer=text_shingle",
             "text_shingle_unigram", "type=text,analyzer=text_shingle_unigram");
-        shardContext = indexService.newQueryShardContext(0, null, () -> 0L, null, emptyMap());
+        shardContext = indexService.newQueryShardContext(0, 0, null, () -> 0L, null, emptyMap());
 
         // parsed queries for "text_shingle_unigram:(foo bar baz)" with query parsers
         // that ignores position length attribute

modules/lang-painless/src/main/java/org/elasticsearch/painless/action/PainlessExecuteAction.java

@@ -556,7 +556,7 @@ private static Response prepareRamIndex(Request request,
                         searcher.setQueryCache(null);
                         final long absoluteStartMillis = System.currentTimeMillis();
                         QueryShardContext context =
-                            indexService.newQueryShardContext(0, searcher, () -> absoluteStartMillis, null, emptyMap());
+                            indexService.newQueryShardContext(0, 0, searcher, () -> absoluteStartMillis, null, emptyMap());
                         return handler.apply(context, indexReader.leaves().get(0));
                     }
                 }

modules/lang-painless/src/test/java/org/elasticsearch/painless/NeedsScoreTests.java

@@ -47,7 +47,7 @@ public void testNeedsScores() {
         contexts.put(NumberSortScript.CONTEXT, Whitelist.BASE_WHITELISTS);
         PainlessScriptEngine service = new PainlessScriptEngine(Settings.EMPTY, contexts);
 
-        QueryShardContext shardContext = index.newQueryShardContext(0, null, () -> 0, null, emptyMap());
+        QueryShardContext shardContext = index.newQueryShardContext(0, 0, null, () -> 0, null, emptyMap());
 
         NumberSortScript.Factory factory = service.compile(null, "1.2", NumberSortScript.CONTEXT, Collections.emptyMap());
         NumberSortScript.LeafFactory ss = factory.newFactory(Collections.emptyMap(), shardContext.lookup());

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

@@ -514,7 +514,7 @@ public void testQueryWithRewrite() throws Exception {
                         XContentType.JSON));
         BytesRef qbSource = doc.rootDoc().getFields(fieldType.queryBuilderField.name())[0].binaryValue();
         QueryShardContext shardContext = indexService.newQueryShardContext(
-            randomInt(20), null, () -> {
+            randomInt(20), 0, null, () -> {
                 throw new UnsupportedOperationException();
             }, null, emptyMap());
         PlainActionFuture<QueryBuilder> future = new PlainActionFuture<>();

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

@@ -259,7 +259,7 @@ public void testRangeQueriesWithNow() throws Exception {
         try (Engine.Searcher searcher = indexService.getShard(0).acquireSearcher("test")) {
             long[] currentTime = new long[] {System.currentTimeMillis()};
             QueryShardContext queryShardContext =
-                indexService.newQueryShardContext(0, searcher, () -> currentTime[0], null, emptyMap());
+                indexService.newQueryShardContext(0, 0, searcher, () -> currentTime[0], null, emptyMap());
 
             BytesReference source = BytesReference.bytes(jsonBuilder().startObject()
                 .field("field1", "value")

rest-api-spec/src/main/resources/rest-api-spec/test/search/90_search_after.yml

@@ -156,8 +156,8 @@
 ---
 "date_nanos":
   - skip:
-      version: " - 7.99.99"
-      reason: fixed in 8.0.0 to be backported to 7.10.0
+      version: " - 7.9.99"
+      reason: fixed in 7.10.0
 
   - do:
       indices.create:
@@ -218,3 +218,27 @@
   - match: {hits.hits.0._source.timestamp: "2019-10-21 00:30:04.828740" }
   - match: {hits.hits.0.sort: [1571617804828740000] }
 
+
+---
+"_shard_doc sort":
+  - skip:
+        version: " - 7.99.99"
+        reason: _shard_doc sort was added in 8.0 (TODO adapt version after backport)
+
+  - do:
+      indices.create:
+        index:  test
+  - do:
+      index:
+        index:  test
+        id:     1
+        body:   { id: 1, foo: bar, age: 18 }
+
+  - do:
+      catch:      /\[_shard_doc\] sort field cannot be used without \[point in time\]/
+      search:
+        index: test
+        body:
+          size: 1
+          sort: [{ _shard_doc }]
+          search_after: [ 0L ]

server/src/main/java/org/elasticsearch/action/admin/indices/template/post/TransportSimulateIndexTemplateAction.java

@@ -183,7 +183,7 @@ public static Template resolveTemplate(final String matchingTemplate, final Stri
                 resolvedAliases, tempClusterState.metadata(), aliasValidator, xContentRegistry,
                 // the context is only used for validation so it's fine to pass fake values for the
                 // shard id and the current timestamp
-                tempIndexService.newQueryShardContext(0, null, () -> 0L, null, emptyMap())));
+                tempIndexService.newQueryShardContext(0, 0, null, () -> 0L, null, emptyMap())));
         Map<String, AliasMetadata> aliasesByName = aliases.stream().collect(
             Collectors.toMap(AliasMetadata::getAlias, Function.identity()));
 

server/src/main/java/org/elasticsearch/action/search/SearchRequest.java

@@ -34,6 +34,9 @@
 import org.elasticsearch.search.builder.PointInTimeBuilder;
 import org.elasticsearch.search.builder.SearchSourceBuilder;
 import org.elasticsearch.search.internal.SearchContext;
+import org.elasticsearch.search.sort.FieldSortBuilder;
+import org.elasticsearch.search.sort.SortBuilder;
+import org.elasticsearch.search.sort.ShardDocSortField;
 import org.elasticsearch.tasks.TaskId;
 
 import java.io.IOException;
@@ -280,6 +283,14 @@ public ActionRequestValidationException validate() {
             if (scroll) {
                 validationException = addValidationError("using [point in time] is not allowed in a scroll context", validationException);
             }
+        } else if (source != null && source.sorts() != null) {
+            for (SortBuilder<?> sortBuilder : source.sorts()) {
+                if (sortBuilder instanceof FieldSortBuilder
+                        && ShardDocSortField.NAME.equals(((FieldSortBuilder) sortBuilder).getFieldName())) {
+                    validationException = addValidationError("[" + FieldSortBuilder.SHARD_DOC_FIELD_NAME
+                        + "] sort field cannot be used without [point in time]", validationException);
+                }
+            }
         }
         return validationException;
     }

server/src/main/java/org/elasticsearch/cluster/metadata/MetadataCreateIndexService.java

@@ -487,7 +487,7 @@ private ClusterState applyCreateIndexRequestWithV1Templates(final ClusterState c
                 MetadataIndexTemplateService.resolveAliases(templates), currentState.metadata(), aliasValidator,
                 // the context is only used for validation so it's fine to pass fake values for the
                 // shard id and the current timestamp
-                xContentRegistry, indexService.newQueryShardContext(0, null, () -> 0L, null, emptyMap())),
+                xContentRegistry, indexService.newQueryShardContext(0, 0, null, () -> 0L, null, emptyMap())),
             templates.stream().map(IndexTemplateMetadata::getName).collect(toList()), metadataTransformer);
     }
 
@@ -520,7 +520,7 @@ private ClusterState applyCreateIndexRequestWithV2Template(final ClusterState cu
                 MetadataIndexTemplateService.resolveAliases(currentState.metadata(), templateName), currentState.metadata(), aliasValidator,
                 // the context is only used for validation so it's fine to pass fake values for the
                 // shard id and the current timestamp
-                xContentRegistry, indexService.newQueryShardContext(0, null, () -> 0L, null, emptyMap())),
+                xContentRegistry, indexService.newQueryShardContext(0, 0, null, () -> 0L, null, emptyMap())),
             Collections.singletonList(templateName), metadataTransformer);
     }
 
@@ -566,7 +566,7 @@ private ClusterState applyCreateIndexRequestWithExistingMetadata(final ClusterSt
                 currentState.metadata(), aliasValidator, xContentRegistry,
                 // the context is only used for validation so it's fine to pass fake values for the
                 // shard id and the current timestamp
-                indexService.newQueryShardContext(0, null, () -> 0L, null, emptyMap())),
+                indexService.newQueryShardContext(0, 0, null, () -> 0L, null, emptyMap())),
             List.of(), metadataTransformer);
     }
 

server/src/main/java/org/elasticsearch/cluster/metadata/MetadataIndexAliasesService.java

@@ -149,8 +149,8 @@ public ClusterState applyAliasActions(ClusterState currentState, Iterable<AliasA
                         }
                         // the context is only used for validation so it's fine to pass fake values for the shard id,
                         // but the current timestamp should be set to real value as we may use `now` in a filtered alias
-                        aliasValidator.validateAliasFilter(alias, filter, indexService.newQueryShardContext(0, null,
-                            () -> System.currentTimeMillis(), null, emptyMap()), xContentRegistry);
+                        aliasValidator.validateAliasFilter(alias, filter, indexService.newQueryShardContext(0, 0,
+                                null, () -> System.currentTimeMillis(), null, emptyMap()), xContentRegistry);
                     }
                 };
                 if (action.apply(newAliasValidator, metadata, index)) {

server/src/main/java/org/elasticsearch/cluster/metadata/MetadataIndexTemplateService.java

@@ -1118,7 +1118,7 @@ private static void validateCompositeTemplate(final ClusterState state,
                     new AliasValidator(),
                     // the context is only used for validation so it's fine to pass fake values for the
                     // shard id and the current timestamp
-                    xContentRegistry, tempIndexService.newQueryShardContext(0, null, () -> 0L, null, emptyMap()));
+                    xContentRegistry, tempIndexService.newQueryShardContext(0, 0, null, () -> 0L, null, emptyMap()));
 
                 // triggers inclusion of _timestamp field and its validation:
                 String indexName = DataStream.BACKING_INDEX_PREFIX + temporaryIndexName;

server/src/main/java/org/elasticsearch/common/lucene/Lucene.java

@@ -93,6 +93,7 @@
 import org.elasticsearch.index.analysis.AnalyzerScope;
 import org.elasticsearch.index.analysis.NamedAnalyzer;
 import org.elasticsearch.index.fielddata.IndexFieldData;
+import org.elasticsearch.search.sort.ShardDocSortField;
 
 import java.io.IOException;
 import java.math.BigInteger;
@@ -566,29 +567,35 @@ public static void writeSortType(StreamOutput out, SortField.Type sortType) thro
         out.writeVInt(sortType.ordinal());
     }
 
-    public static void writeSortField(StreamOutput out, SortField sortField) throws IOException {
+    /**
+     * Returns the generic version of the provided {@link SortField} that
+     * can be used to merge documents coming from different shards.
+     */
+    private static SortField rewriteMergeSortField(SortField sortField) {
         if (sortField.getClass() == GEO_DISTANCE_SORT_TYPE_CLASS) {
-            // for geo sorting, we replace the SortField with a SortField that assumes a double field.
-            // this works since the SortField is only used for merging top docs
             SortField newSortField = new SortField(sortField.getField(), SortField.Type.DOUBLE);
             newSortField.setMissingValue(sortField.getMissingValue());
-            sortField = newSortField;
+            return newSortField;
         } else if (sortField.getClass() == SortedSetSortField.class) {
-            // for multi-valued sort field, we replace the SortedSetSortField with a simple SortField.
-            // It works because the sort field is only used to merge results from different shards.
             SortField newSortField = new SortField(sortField.getField(), SortField.Type.STRING, sortField.getReverse());
             newSortField.setMissingValue(sortField.getMissingValue());
-            sortField = newSortField;
+            return newSortField;
         } else if (sortField.getClass() == SortedNumericSortField.class) {
-            // for multi-valued sort field, we replace the SortedSetSortField with a simple SortField.
-            // It works because the sort field is only used to merge results from different shards.
             SortField newSortField = new SortField(sortField.getField(),
                 ((SortedNumericSortField) sortField).getNumericType(),
                 sortField.getReverse());
             newSortField.setMissingValue(sortField.getMissingValue());
-            sortField = newSortField;
+            return newSortField;
+        } else if (sortField.getClass() == ShardDocSortField.class) {
+            SortField newSortField = new SortField(sortField.getField(), SortField.Type.LONG, sortField.getReverse());
+            return newSortField;
+        } else {
+            return sortField;
         }
+    }
 
+    public static void writeSortField(StreamOutput out, SortField sortField) throws IOException {
+        sortField = rewriteMergeSortField(sortField);
         if (sortField.getClass() != SortField.class) {
             throw new IllegalArgumentException("Cannot serialize SortField impl [" + sortField + "]");
         }

server/src/main/java/org/elasticsearch/index/IndexService.java

@@ -192,7 +192,7 @@ public IndexService(
             assert indexAnalyzers != null;
             this.mapperService = new MapperService(indexSettings, indexAnalyzers, xContentRegistry, similarityService, mapperRegistry,
                 // we parse all percolator queries as they would be parsed on shard 0
-                () -> newQueryShardContext(0, null, System::currentTimeMillis, null, emptyMap()), idFieldDataEnabled, scriptService);
+                () -> newQueryShardContext(0, 0, null, System::currentTimeMillis, null, emptyMap()), idFieldDataEnabled, scriptService);
             this.indexFieldData = new IndexFieldDataService(indexSettings, indicesFieldDataCache, circuitBreakerService, mapperService);
             if (indexSettings.getIndexSortConfig().hasIndexSort()) {
                 // we delay the actual creation of the sort order for this index because the mapping has not been merged yet.
@@ -588,6 +588,7 @@ public IndexSettings getIndexSettings() {
      */
     public QueryShardContext newQueryShardContext(
         int shardId,
+        int shardRequestIndex,
         IndexSearcher searcher,
         LongSupplier nowInMillis,
         String clusterAlias,
@@ -596,9 +597,26 @@ public QueryShardContext newQueryShardContext(
         final SearchIndexNameMatcher indexNameMatcher =
             new SearchIndexNameMatcher(index().getName(), clusterAlias, clusterService, expressionResolver);
         return new QueryShardContext(
-            shardId, indexSettings, bigArrays, indexCache.bitsetFilterCache(), indexFieldData::getForField, mapperService(),
-            similarityService(), scriptService, xContentRegistry, namedWriteableRegistry, client, searcher, nowInMillis, clusterAlias,
-            indexNameMatcher, allowExpensiveQueries, valuesSourceRegistry, runtimeMappings);
+            shardId,
+            shardRequestIndex,
+            indexSettings,
+            bigArrays,
+            indexCache.bitsetFilterCache(),
+            indexFieldData::getForField,
+            mapperService(),
+            similarityService(),
+            scriptService,
+            xContentRegistry,
+            namedWriteableRegistry,
+            client,
+            searcher,
+            nowInMillis,
+            clusterAlias,
+            indexNameMatcher,
+            allowExpensiveQueries,
+            valuesSourceRegistry,
+            runtimeMappings
+        );
     }
 
     /**

server/src/main/java/org/elasticsearch/index/query/QueryShardContext.java

@@ -94,6 +94,7 @@ public class QueryShardContext extends QueryRewriteContext {
     private final BitsetFilterCache bitsetFilterCache;
     private final TriFunction<MappedFieldType, String, Supplier<SearchLookup>, IndexFieldData<?>> indexFieldDataService;
     private final int shardId;
+    private final int shardRequestIndex;
     private final IndexSearcher searcher;
     private boolean cacheable = true;
     private final SetOnce<Boolean> frozen = new SetOnce<>();
@@ -114,6 +115,7 @@ public class QueryShardContext extends QueryRewriteContext {
      */
     public QueryShardContext(
         int shardId,
+        int shardRequestIndex,
         IndexSettings indexSettings,
         BigArrays bigArrays,
         BitsetFilterCache bitsetFilterCache,
@@ -134,6 +136,7 @@ public QueryShardContext(
     ) {
         this(
             shardId,
+            shardRequestIndex,
             indexSettings,
             bigArrays,
             bitsetFilterCache,
@@ -158,13 +161,30 @@ public QueryShardContext(
     }
 
     public QueryShardContext(QueryShardContext source) {
-        this(source.shardId, source.indexSettings, source.bigArrays, source.bitsetFilterCache, source.indexFieldDataService,
-            source.mapperService, source.similarityService, source.scriptService, source.getXContentRegistry(),
-            source.getWriteableRegistry(), source.client, source.searcher, source.nowInMillis, source.indexNameMatcher,
-            source.fullyQualifiedIndex, source.allowExpensiveQueries, source.valuesSourceRegistry, source.runtimeMappings);
+        this(
+            source.shardId,
+            source.shardRequestIndex,
+            source.indexSettings,
+            source.bigArrays,
+            source.bitsetFilterCache,
+            source.indexFieldDataService,
+            source.mapperService,
+            source.similarityService,
+            source.scriptService,
+            source.getXContentRegistry(),
+            source.getWriteableRegistry(),
+            source.client, source.searcher,
+            source.nowInMillis,
+            source.indexNameMatcher,
+            source.fullyQualifiedIndex,
+            source.allowExpensiveQueries,
+            source.valuesSourceRegistry,
+            source.runtimeMappings
+        );
     }
 
     private QueryShardContext(int shardId,
+                              int shardRequestIndex,
                               IndexSettings indexSettings,
                               BigArrays bigArrays,
                               BitsetFilterCache bitsetFilterCache,
@@ -184,6 +204,7 @@ private QueryShardContext(int shardId,
                               Map<String, MappedFieldType> runtimeMappings) {
         super(xContentRegistry, namedWriteableRegistry, client, nowInMillis);
         this.shardId = shardId;
+        this.shardRequestIndex = shardRequestIndex;
         this.similarityService = similarityService;
         this.mapperService = mapperService;
         this.bigArrays = bigArrays;
@@ -520,6 +541,14 @@ public int getShardId() {
         return shardId;
     }
 
+    /**
+     * Returns the shard request ordinal that is used by the main search request
+     * to reference this shard.
+     */
+    public int getShardRequestIndex() {
+        return shardRequestIndex;
+    }
+
     @Override
     public final long nowInMillis() {
         failIfFrozen();

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

@@ -166,7 +166,8 @@ final class DefaultSearchContext extends SearchContext {
         this.timeout = timeout;
         queryShardContext = indexService.newQueryShardContext(
             request.shardId().id(),
-            this.searcher,
+            request.shardRequestIndex(),
+            searcher,
             request::nowInMillis,
             shardTarget.getClusterAlias(),
             request.getRuntimeMappings()

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

@@ -1174,8 +1174,8 @@ private CanMatchResponse canMatch(ShardSearchRequest request, boolean checkRefre
             }
 
             try (canMatchSearcher) {
-                QueryShardContext context = indexService.newQueryShardContext(request.shardId().id(), canMatchSearcher,
-                    request::nowInMillis, request.getClusterAlias(), request.getRuntimeMappings());
+                QueryShardContext context = indexService.newQueryShardContext(request.shardId().id(), 0,
+                        canMatchSearcher, request::nowInMillis, request.getClusterAlias(), request.getRuntimeMappings());
                 Rewriteable.rewrite(request.getRewriteable(), context, false);
                 final boolean aliasFilterCanMatch = request.getAliasFilter()
                     .getQueryBuilder() instanceof MatchNoneQueryBuilder == false;