[8.x] Don't skip shards in coord rewrite if timestamp is an alias (#117271) (#117912)

The coordinator rewrite has logic to skip indices if the provided date range
filter is not within the min and max range of all of its shards. This mechanism
is enabled for event.ingested and @timestamp fields, against searchable snapshots.

We have basic checks that such fields need to be of date field type, yet if they
are defined as alias of a date field, their range will be empty, which indicates
that the shards are empty, and the coord rewrite logic resolves the alias and
ends up skipping shards that may have matching docs.

This commit adds an explicit check that declares the range UNKNOWN instead of EMPTY
in these circumstances. The same check is also performed in the coord rewrite logic,
so that shards are no longer skipped by mistake.

docs/changelog/117271.yaml

@@ -0,0 +1,5 @@
+pr: 117271
+summary: Don't skip shards in coord rewrite if timestamp is an alias
+area: Search
+type: bug
+issues: []

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

@@ -438,6 +438,7 @@ public class RangeQueryBuilder extends AbstractQueryBuilder<RangeQueryBuilder> i
     protected MappedFieldType.Relation getRelation(final CoordinatorRewriteContext coordinatorRewriteContext) {
         final MappedFieldType fieldType = coordinatorRewriteContext.getFieldType(fieldName);
         if (fieldType instanceof final DateFieldMapper.DateFieldType dateFieldType) {
+            assert fieldName.equals(fieldType.name());
             IndexLongFieldRange fieldRange = coordinatorRewriteContext.getFieldRange(fieldName);
             if (fieldRange.isComplete() == false || fieldRange == IndexLongFieldRange.EMPTY) {
                 // if not all shards for this (frozen) index have reported ranges to cluster state, OR if they

server/src/main/java/org/elasticsearch/index/shard/IndexShard.java

@@ -2258,8 +2258,8 @@ public class IndexShard extends AbstractIndexShardComponent implements IndicesCl
             return ShardLongFieldRange.UNKNOWN; // no mapper service, no idea if the field even exists
         }
         final MappedFieldType mappedFieldType = mapperService().fieldType(fieldName);
-        if (mappedFieldType instanceof DateFieldMapper.DateFieldType == false) {
-            return ShardLongFieldRange.UNKNOWN; // field missing or not a date
+        if (mappedFieldType instanceof DateFieldMapper.DateFieldType == false || mappedFieldType.name().equals(fieldName) == false) {
+            return ShardLongFieldRange.UNKNOWN; // field is missing, an alias (as the field type has a different name) or not a date field
         }
         if (mappedFieldType.isIndexed() == false) {
             return ShardLongFieldRange.UNKNOWN; // range information missing

server/src/main/java/org/elasticsearch/indices/TimestampFieldMapperService.java

@@ -166,11 +166,13 @@ public class TimestampFieldMapperService extends AbstractLifecycleComponent impl
         DateFieldMapper.DateFieldType eventIngestedFieldType = null;
 
         MappedFieldType mappedFieldType = mapperService.fieldType(DataStream.TIMESTAMP_FIELD_NAME);
-        if (mappedFieldType instanceof DateFieldMapper.DateFieldType dateFieldType) {
+        if (mappedFieldType instanceof DateFieldMapper.DateFieldType dateFieldType
+            && dateFieldType.name().equals(DataStream.TIMESTAMP_FIELD_NAME)) {
             timestampFieldType = dateFieldType;
         }
         mappedFieldType = mapperService.fieldType(IndexMetadata.EVENT_INGESTED_FIELD_NAME);
-        if (mappedFieldType instanceof DateFieldMapper.DateFieldType dateFieldType) {
+        if (mappedFieldType instanceof DateFieldMapper.DateFieldType dateFieldType
+            && dateFieldType.name().equals(IndexMetadata.EVENT_INGESTED_FIELD_NAME)) {
             eventIngestedFieldType = dateFieldType;
         }
         if (timestampFieldType == null && eventIngestedFieldType == null) {

x-pack/plugin/searchable-snapshots/src/internalClusterTest/java/org/elasticsearch/xpack/searchablesnapshots/SearchableSnapshotsCanMatchOnCoordinatorIntegTests.java

@@ -15,6 +15,7 @@ import org.elasticsearch.action.search.SearchResponse;
 import org.elasticsearch.action.search.SearchShardsGroup;
 import org.elasticsearch.action.search.SearchShardsRequest;
 import org.elasticsearch.action.search.SearchShardsResponse;
+import org.elasticsearch.action.search.SearchType;
 import org.elasticsearch.action.search.TransportSearchShardsAction;
 import org.elasticsearch.blobcache.shared.SharedBlobCacheService;
 import org.elasticsearch.cluster.metadata.DataStream;
@@ -1100,6 +1101,119 @@ public class SearchableSnapshotsCanMatchOnCoordinatorIntegTests extends BaseFroz
         }
     }
 
+    public void testTimestampAsAlias() throws Exception {
+        doTestCoordRewriteWithAliasField("@timestamp");
+    }
+
+    public void testEventIngestedAsAlias() throws Exception {
+        doTestCoordRewriteWithAliasField("event.ingested");
+    }
+
+    private void doTestCoordRewriteWithAliasField(String aliasFieldName) throws Exception {
+        internalCluster().startMasterOnlyNode();
+        internalCluster().startCoordinatingOnlyNode(Settings.EMPTY);
+        final String dataNodeHoldingRegularIndex = internalCluster().startDataOnlyNode();
+        final String dataNodeHoldingSearchableSnapshot = internalCluster().startDataOnlyNode();
+
+        String timestampFieldName = randomAlphaOfLengthBetween(3, 10);
+        String[] indices = new String[] { "index-0001", "index-0002" };
+        for (String index : indices) {
+            Settings extraSettings = Settings.builder()
+                .put(INDEX_ROUTING_REQUIRE_GROUP_SETTING.getConcreteSettingForNamespace("_name").getKey(), dataNodeHoldingRegularIndex)
+                .build();
+
+            assertAcked(
+                indicesAdmin().prepareCreate(index)
+                    .setMapping(
+                        XContentFactory.jsonBuilder()
+                            .startObject()
+                            .startObject("properties")
+
+                            .startObject(timestampFieldName)
+                            .field("type", "date")
+                            .endObject()
+
+                            .startObject(aliasFieldName)
+                            .field("type", "alias")
+                            .field("path", timestampFieldName)
+                            .endObject()
+
+                            .endObject()
+                            .endObject()
+                    )
+                    .setSettings(indexSettingsNoReplicas(1).put(INDEX_SOFT_DELETES_SETTING.getKey(), true).put(extraSettings))
+            );
+        }
+        ensureGreen(indices);
+
+        for (String index : indices) {
+            final List<IndexRequestBuilder> indexRequestBuilders = new ArrayList<>();
+            for (int i = 0; i < 10; i++) {
+                indexRequestBuilders.add(prepareIndex(index).setSource(timestampFieldName, "2024-11-19T08:08:08Z"));
+            }
+            indexRandom(true, false, indexRequestBuilders);
+
+            assertThat(
+                indicesAdmin().prepareForceMerge(index).setOnlyExpungeDeletes(true).setFlush(true).get().getFailedShards(),
+                equalTo(0)
+            );
+            refresh(index);
+            forceMerge();
+        }
+
+        final String repositoryName = randomAlphaOfLength(10).toLowerCase(Locale.ROOT);
+        createRepository(repositoryName, "mock");
+
+        final SnapshotId snapshotId = createSnapshot(repositoryName, "snapshot-1", List.of(indices[0])).snapshotId();
+        assertAcked(indicesAdmin().prepareDelete(indices[0]));
+
+        // Block the repository for the node holding the searchable snapshot shards
+        // to delay its restore
+        blockDataNode(repositoryName, dataNodeHoldingSearchableSnapshot);
+
+        // Force the searchable snapshot to be allocated in a particular node
+        Settings restoredIndexSettings = Settings.builder()
+            .put(INDEX_ROUTING_REQUIRE_GROUP_SETTING.getConcreteSettingForNamespace("_name").getKey(), dataNodeHoldingSearchableSnapshot)
+            .build();
+
+        String mountedIndex = indices[0] + "-mounted";
+        final MountSearchableSnapshotRequest mountRequest = new MountSearchableSnapshotRequest(
+            TEST_REQUEST_TIMEOUT,
+            mountedIndex,
+            repositoryName,
+            snapshotId.getName(),
+            indices[0],
+            restoredIndexSettings,
+            Strings.EMPTY_ARRAY,
+            false,
+            randomFrom(MountSearchableSnapshotRequest.Storage.values())
+        );
+        client().execute(MountSearchableSnapshotAction.INSTANCE, mountRequest).actionGet();
+
+        // Allow the searchable snapshots to be finally mounted
+        unblockNode(repositoryName, dataNodeHoldingSearchableSnapshot);
+        waitUntilRecoveryIsDone(mountedIndex);
+        ensureGreen(mountedIndex);
+
+        String[] fieldsToQuery = new String[] { timestampFieldName, aliasFieldName };
+        for (String fieldName : fieldsToQuery) {
+            RangeQueryBuilder rangeQuery = QueryBuilders.rangeQuery(fieldName).from("2024-11-01T00:00:00.000000000Z", true);
+            SearchRequest request = new SearchRequest().searchType(SearchType.QUERY_THEN_FETCH)
+                .source(new SearchSourceBuilder().query(rangeQuery));
+            if (randomBoolean()) {
+                // pre_filter_shard_size default to 1 because there are read-only indices in the mix. It does not hurt to force it though.
+                request.setPreFilterShardSize(1);
+            }
+            assertResponse(client().search(request), searchResponse -> {
+                assertThat(searchResponse.getSuccessfulShards(), equalTo(2));
+                assertThat(searchResponse.getFailedShards(), equalTo(0));
+                assertThat(searchResponse.getSkippedShards(), equalTo(0));
+                assertThat(searchResponse.getTotalShards(), equalTo(2));
+                assertThat(searchResponse.getHits().getTotalHits().value, equalTo(20L));
+            });
+        }
+    }
+
     private void createIndexWithTimestampAndEventIngested(String indexName, int numShards, Settings extraSettings) throws IOException {
         assertAcked(
             indicesAdmin().prepareCreate(indexName)
@@ -1148,8 +1262,7 @@ public class SearchableSnapshotsCanMatchOnCoordinatorIntegTests extends BaseFroz
         ensureGreen(index);
     }
 
-    private void indexDocumentsWithOnlyOneTimestampField(String timestampField, String index, int docCount, String timestampTemplate)
-        throws Exception {
+    private void indexDocumentsWithOnlyOneTimestampField(String timestampField, String index, int docCount, String timestampTemplate) {
         final List<IndexRequestBuilder> indexRequestBuilders = new ArrayList<>();
         for (int i = 0; i < docCount; i++) {
             indexRequestBuilders.add(
@@ -1173,8 +1286,7 @@ public class SearchableSnapshotsCanMatchOnCoordinatorIntegTests extends BaseFroz
         forceMerge();
     }
 
-    private void indexDocumentsWithTimestampAndEventIngestedDates(String indexName, int docCount, String timestampTemplate)
-        throws Exception {
+    private void indexDocumentsWithTimestampAndEventIngestedDates(String indexName, int docCount, String timestampTemplate) {
 
         final List<IndexRequestBuilder> indexRequestBuilders = new ArrayList<>();
         for (int i = 0; i < docCount; i++) {
@@ -1211,7 +1323,7 @@ public class SearchableSnapshotsCanMatchOnCoordinatorIntegTests extends BaseFroz
         forceMerge();
     }
 
-    private IndexMetadata getIndexMetadata(String indexName) {
+    private static IndexMetadata getIndexMetadata(String indexName) {
         return clusterAdmin().prepareState(TEST_REQUEST_TIMEOUT)
             .clear()
             .setMetadata(true)
@@ -1222,7 +1334,7 @@ public class SearchableSnapshotsCanMatchOnCoordinatorIntegTests extends BaseFroz
             .index(indexName);
     }
 
-    private void waitUntilRecoveryIsDone(String index) throws Exception {
+    private static void waitUntilRecoveryIsDone(String index) throws Exception {
         assertBusy(() -> {
             RecoveryResponse recoveryResponse = indicesAdmin().prepareRecoveries(index).get();
             assertThat(recoveryResponse.hasRecoveries(), equalTo(true));