Allow querying index_mode (elastic#110676)

This change allows querying the `index.mode` setting via a new 
`_index_mode` metadata field, enabling APIs such as `field_caps` or
`resolve_indices` to target indices that are either time_series or logs
only. This approach avoids adding and handling a new parameter for
`index_mode` in these APIs. Both ES|QL and the `_search` API should also
work with this new field.

Author: dnhatn

benchmarks/src/main/java/org/elasticsearch/benchmark/compute/operator/ValuesSourceReaderBenchmark.java

@@ -41,6 +41,7 @@
 import org.elasticsearch.compute.lucene.ValuesSourceReaderOperator;
 import org.elasticsearch.compute.operator.topn.TopNOperator;
 import org.elasticsearch.core.IOUtils;
+import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.index.IndexVersion;
 import org.elasticsearch.index.mapper.BlockLoader;
 import org.elasticsearch.index.mapper.FieldNamesFieldMapper;
@@ -189,6 +190,11 @@ public String indexName() {
                     return "benchmark";
                 }
 
+                @Override
+                public IndexSettings indexSettings() {
+                    throw new UnsupportedOperationException();
+                }
+
                 @Override
                 public MappedFieldType.FieldExtractPreference fieldExtractPreference() {
                     return MappedFieldType.FieldExtractPreference.NONE;

docs/changelog/110676.yaml

@@ -0,0 +1,5 @@
+pr: 110676
+summary: Allow querying `index_mode`
+area: Mapping
+type: enhancement
+issues: []

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

@@ -655,6 +655,7 @@ public <IFD extends IndexFieldData<?>> IFD getForField(
                 IndexFieldData.Builder builder = fieldType.fielddataBuilder(
                     new FieldDataContext(
                         delegate.getFullyQualifiedIndex().getName(),
+                        delegate.getIndexSettings(),
                         delegate::lookup,
                         this::sourcePath,
                         fielddataOperation

rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/field_caps/70_index_mode.yml

@@ -0,0 +1,59 @@
+---
+setup:
+  - requires:
+      cluster_features: "mapper.query_index_mode"
+      reason: "require index_mode"
+
+  - do:
+      indices.create:
+        index: test_metrics
+        body:
+          settings:
+            index:
+              mode: time_series
+              routing_path: [container]
+              time_series:
+                start_time: 2021-04-28T00:00:00Z
+                end_time: 2021-04-29T00:00:00Z
+          mappings:
+            properties:
+              "@timestamp":
+                type: date
+              container:
+                type: keyword
+                time_series_dimension: true
+
+  - do:
+      indices.create:
+        index: test
+        body:
+          mappings:
+            properties:
+              "@timestamp":
+                type: date
+
+---
+Field-caps:
+  - do:
+      field_caps:
+        index: "test*"
+        fields: "*"
+        body: { index_filter: { term: { _index_mode: "time_series" } } }
+  - match: { indices: [ "test_metrics" ] }
+  - do:
+      field_caps:
+        index: "test*"
+        fields: "*"
+        body: { index_filter: { term: { _index_mode: "logs" } } }
+  - match: { indices: [ ] }
+  - do:
+      field_caps:
+        index: "test*"
+        fields: "*"
+        body: { index_filter: { term: { _index_mode: "standard" } } }
+  - match: { indices: [ "test" ] }
+  - do:
+      field_caps:
+        index: "test*"
+        fields: "*"
+  - match: { indices: [ "test" , "test_metrics" ] }

rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/nodes.stats/11_indices_metrics.yml

@@ -417,7 +417,7 @@
 
   - requires:
       test_runner_features: [arbitrary_key]
-      cluster_features: ["mapper.track_ignored_source"]
+      cluster_features: ["mapper.query_index_mode"]
       reason:  "_ignored_source added to mappings"
 
   - do:
@@ -478,34 +478,35 @@
   # 6. _ignored
   # 7. _ignored_source
   # 8. _index
-  # 9. _nested_path
-  # 10. _routing
-  # 11. _seq_no
-  # 12. _source
-  # 13. _tier
-  # 14. _version
-  # 15. @timestamp
-  # 16. authors.age
-  # 17. authors.company
-  # 18. authors.company.keyword
-  # 19. authors.name.last_name
-  # 20. authors.name.first_name
-  # 21. authors.name.full_name
-  # 22. link
-  # 23. title
-  # 24. url
+  # 9. _index_mode
+  # 10. _nested_path
+  # 11. _routing
+  # 12. _seq_no
+  # 13. _source
+  # 14. _tier
+  # 15. _version
+  # 16. @timestamp
+  # 17. authors.age
+  # 18. authors.company
+  # 19. authors.company.keyword
+  # 20. authors.name.last_name
+  # 21. authors.name.first_name
+  # 22. authors.name.full_name
+  # 23. link
+  # 24. title
+  # 25. url
   # Object mappers:
-  # 25. authors
-  # 26. authors.name
+  # 26. authors
+  # 27. authors.name
   # Runtime field mappers:
-  # 27. a_source_field
+  # 28. a_source_field
 
-  - gte: { nodes.$node_id.indices.mappings.total_count: 27 }
+  - gte: { nodes.$node_id.indices.mappings.total_count: 28 }
   - is_true: nodes.$node_id.indices.mappings.total_estimated_overhead
   - gte: { nodes.$node_id.indices.mappings.total_estimated_overhead_in_bytes: 26624 }
-  - match: { nodes.$node_id.indices.indices.index1.mappings.total_count: 27 }
+  - match: { nodes.$node_id.indices.indices.index1.mappings.total_count: 28 }
   - is_true: nodes.$node_id.indices.indices.index1.mappings.total_estimated_overhead
-  - match: { nodes.$node_id.indices.indices.index1.mappings.total_estimated_overhead_in_bytes: 27648 }
+  - match: { nodes.$node_id.indices.indices.index1.mappings.total_estimated_overhead_in_bytes: 28672 }
 
 ---
 "indices mappings does not exist in shards level":

rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/tsdb/40_search.yml

@@ -337,3 +337,20 @@ sort by tsid:
 
   - match: {hits.hits.7.sort: ["KCjEJ9R_BgO8TRX2QOd6dpR12oDh--qoyNZRQPy43y34Qdy2dpsyG0o", 1619635864467]}
   - match: {hits.hits.7.fields._tsid: [ "KCjEJ9R_BgO8TRX2QOd6dpR12oDh--qoyNZRQPy43y34Qdy2dpsyG0o"]}
+
+---
+aggs by index_mode:
+  - requires:
+      cluster_features: ["mapper.query_index_mode"]
+      reason: require _index_mode metadata field
+  - do:
+      search:
+        index: test
+        body:
+          aggs:
+            modes:
+              terms:
+                field: "_index_mode"
+  - match: {aggregations.modes.buckets.0.key: "time_series"}
+  - match: {aggregations.modes.buckets.0.doc_count: 8}
+

server/src/main/java/org/elasticsearch/index/fielddata/FieldDataContext.java

@@ -8,6 +8,7 @@
 
 package org.elasticsearch.index.fielddata;
 
+import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.index.mapper.MappedFieldType;
 import org.elasticsearch.search.lookup.SearchLookup;
 
@@ -25,6 +26,7 @@
  */
 public record FieldDataContext(
     String fullyQualifiedIndexName,
+    IndexSettings indexSettings,
     Supplier<SearchLookup> lookupSupplier,
     Function<String, Set<String>> sourcePathsLookup,
     MappedFieldType.FielddataOperation fielddataOperation
@@ -38,11 +40,8 @@ public record FieldDataContext(
      * @param reason the reason that runtime fields are not supported
      */
     public static FieldDataContext noRuntimeFields(String reason) {
-        return new FieldDataContext(
-            "",
-            () -> { throw new UnsupportedOperationException("Runtime fields not supported for [" + reason + "]"); },
-            Set::of,
-            MappedFieldType.FielddataOperation.SEARCH
-        );
+        return new FieldDataContext("", null, () -> {
+            throw new UnsupportedOperationException("Runtime fields not supported for [" + reason + "]");
+        }, Set::of, MappedFieldType.FielddataOperation.SEARCH);
     }
 }

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

@@ -161,7 +161,13 @@ private static void executeIndexTimeScripts(DocumentParserContext context) {
         SearchLookup searchLookup = new SearchLookup(
             context.mappingLookup().indexTimeLookup()::get,
             (ft, lookup, fto) -> ft.fielddataBuilder(
-                new FieldDataContext(context.indexSettings().getIndex().getName(), lookup, context.mappingLookup()::sourcePaths, fto)
+                new FieldDataContext(
+                    context.indexSettings().getIndex().getName(),
+                    context.indexSettings(),
+                    lookup,
+                    context.mappingLookup()::sourcePaths,
+                    fto
+                )
             ).build(new IndexFieldDataCache.None(), new NoneCircuitBreakerService()),
             (ctx, doc) -> Source.fromBytes(context.sourceToParse().source())
         );

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

@@ -0,0 +1,119 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+package org.elasticsearch.index.mapper;
+
+import org.apache.lucene.search.MatchAllDocsQuery;
+import org.apache.lucene.search.Query;
+import org.apache.lucene.util.BytesRef;
+import org.elasticsearch.common.regex.Regex;
+import org.elasticsearch.features.NodeFeature;
+import org.elasticsearch.index.fielddata.FieldData;
+import org.elasticsearch.index.fielddata.FieldDataContext;
+import org.elasticsearch.index.fielddata.IndexFieldData;
+import org.elasticsearch.index.fielddata.ScriptDocValues;
+import org.elasticsearch.index.fielddata.plain.ConstantIndexFieldData;
+import org.elasticsearch.index.query.QueryRewriteContext;
+import org.elasticsearch.index.query.SearchExecutionContext;
+import org.elasticsearch.script.field.DelegateDocValuesField;
+import org.elasticsearch.search.aggregations.support.CoreValuesSourceType;
+import org.elasticsearch.search.fetch.StoredFieldsSpec;
+import org.elasticsearch.search.lookup.Source;
+
+import java.util.Collections;
+import java.util.List;
+
+public class IndexModeFieldMapper extends MetadataFieldMapper {
+
+    static final NodeFeature QUERYING_INDEX_MODE = new NodeFeature("mapper.query_index_mode");
+
+    public static final String NAME = "_index_mode";
+
+    public static final String CONTENT_TYPE = "_index_mode";
+
+    private static final IndexModeFieldMapper INSTANCE = new IndexModeFieldMapper();
+
+    public static final TypeParser PARSER = new FixedTypeParser(c -> INSTANCE);
+
+    static final class IndexModeFieldType extends ConstantFieldType {
+
+        static final IndexModeFieldType INSTANCE = new IndexModeFieldType();
+
+        private IndexModeFieldType() {
+            super(NAME, Collections.emptyMap());
+        }
+
+        @Override
+        public String typeName() {
+            return CONTENT_TYPE;
+        }
+
+        @Override
+        protected boolean matches(String pattern, boolean caseInsensitive, QueryRewriteContext context) {
+            final String indexMode = context.getIndexSettings().getMode().getName();
+            return Regex.simpleMatch(pattern, indexMode, caseInsensitive);
+        }
+
+        @Override
+        public Query existsQuery(SearchExecutionContext context) {
+            return new MatchAllDocsQuery();
+        }
+
+        @Override
+        public IndexFieldData.Builder fielddataBuilder(FieldDataContext fieldDataContext) {
+            final String indexMode = fieldDataContext.indexSettings().getMode().getName();
+            return new ConstantIndexFieldData.Builder(
+                indexMode,
+                name(),
+                CoreValuesSourceType.KEYWORD,
+                (dv, n) -> new DelegateDocValuesField(
+                    new ScriptDocValues.Strings(new ScriptDocValues.StringsSupplier(FieldData.toString(dv))),
+                    n
+                )
+            );
+        }
+
+        @Override
+        public BlockLoader blockLoader(BlockLoaderContext blContext) {
+            final String indexMode = blContext.indexSettings().getMode().getName();
+            return BlockLoader.constantBytes(new BytesRef(indexMode));
+        }
+
+        @Override
+        public ValueFetcher valueFetcher(SearchExecutionContext context, String format) {
+            return new ValueFetcher() {
+                private final List<Object> indexMode = List.of(context.getIndexSettings().getMode().getName());
+
+                @Override
+                public List<Object> fetchValues(Source source, int doc, List<Object> ignoredValues) {
+                    return indexMode;
+                }
+
+                @Override
+                public StoredFieldsSpec storedFieldsSpec() {
+                    return StoredFieldsSpec.NO_REQUIREMENTS;
+                }
+            };
+        }
+
+    }
+
+    public IndexModeFieldMapper() {
+        super(IndexModeFieldType.INSTANCE);
+    }
+
+    @Override
+    protected String contentType() {
+        return CONTENT_TYPE;
+    }
+
+    @Override
+    public SourceLoader.SyntheticFieldLoader syntheticFieldLoader() {
+        return SourceLoader.SyntheticFieldLoader.NOTHING;
+    }
+}

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

@@ -35,6 +35,7 @@
 import org.elasticsearch.common.time.DateMathParser;
 import org.elasticsearch.common.unit.Fuzziness;
 import org.elasticsearch.core.Nullable;
+import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.index.fielddata.FieldDataContext;
 import org.elasticsearch.index.fielddata.IndexFieldData;
 import org.elasticsearch.index.query.DistanceFeatureQueryBuilder;
@@ -693,6 +694,11 @@ public interface BlockLoaderContext {
          */
         String indexName();
 
+        /**
+         * The index settings of the index
+         */
+        IndexSettings indexSettings();
+
         /**
          * How the field should be extracted into the BlockLoader. The default is {@link FieldExtractPreference#NONE}, which means
          * that the field type can choose where to load the field from. However, in some cases, the caller may have a preference.