Add support for Wildcard Index.

Add WildcardIndexed annotation and the programatic WildcardIndex.

Closes #3225
Original pull request: #3671.

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/IndexConverters.java

@@ -115,6 +115,10 @@ private static Converter<IndexDefinition, IndexOptions> getIndexDefinitionIndexO
 				ops = ops.collation(fromDocument(indexOptions.get("collation", Document.class)));
 			}
 
+			if(indexOptions.containsKey("wildcardProjection")) {
+				ops.wildcardProjection(indexOptions.get("wildcardProjection", Document.class));
+			}
+
 			return ops;
 		};
 	}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/index/IndexField.java

@@ -29,7 +29,7 @@
 public final class IndexField {
 
 	enum Type {
-		GEO, TEXT, DEFAULT, HASH;
+		GEO, TEXT, DEFAULT, HASH, WILDCARD;
 	}
 
 	private final String key;
@@ -48,7 +48,7 @@ private IndexField(String key, @Nullable Direction direction, @Nullable Type typ
 		if (Type.GEO.equals(type) || Type.TEXT.equals(type)) {
 			Assert.isNull(direction, "Geo/Text indexes must not have a direction!");
 		} else {
-			if (!Type.HASH.equals(type)) {
+			if (!(Type.HASH.equals(type) || Type.WILDCARD.equals(type))) {
 				Assert.notNull(direction, "Default indexes require a direction");
 			}
 		}
@@ -77,6 +77,17 @@ static IndexField hashed(String key) {
 		return new IndexField(key, null, Type.HASH);
 	}
 
+	/**
+	 * Creates a {@literal wildcard} {@link IndexField} for the given key.
+	 *
+	 * @param key must not be {@literal null} or empty.
+	 * @return new instance of {@link IndexField}.
+	 * @since 3.3
+	 */
+	static IndexField wildcard(String key) {
+		return new IndexField(key, null, Type.WILDCARD);
+	}
+
 	/**
 	 * Creates a geo {@link IndexField} for the given key.
 	 *
@@ -142,6 +153,16 @@ public boolean isHashed() {
 		return Type.HASH.equals(type);
 	}
 
+	/**
+	 * Returns whether the {@link IndexField} is contains a {@literal wildcard} expression.
+	 *
+	 * @return {@literal true} if {@link IndexField} contains a wildcard {@literal $**}.
+	 * @since 3.3
+	 */
+	public boolean isWildcard() {
+		return Type.WILDCARD.equals(type);
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * @see java.lang.Object#equals(java.lang.Object)

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/index/IndexInfo.java

@@ -55,6 +55,7 @@ public class IndexInfo {
 	private @Nullable Duration expireAfter;
 	private @Nullable String partialFilterExpression;
 	private @Nullable Document collation;
+	private @Nullable Document wildcardProjection;
 
 	public IndexInfo(List<IndexField> indexFields, String name, boolean unique, boolean sparse, String language) {
 
@@ -99,6 +100,8 @@ public static IndexInfo indexInfoOf(Document sourceDocument) {
 
 				if (ObjectUtils.nullSafeEquals("hashed", value)) {
 					indexFields.add(IndexField.hashed(key));
+				} else if (key.contains("$**")) {
+					indexFields.add(IndexField.wildcard(key));
 				} else {
 
 					Double keyValue = new Double(value.toString());
@@ -131,6 +134,10 @@ public static IndexInfo indexInfoOf(Document sourceDocument) {
 			info.expireAfter = Duration.ofSeconds(NumberUtils.convertNumberToTargetClass(expireAfterSeconds, Long.class));
 		}
 
+		if (sourceDocument.containsKey("wildcardProjection")) {
+			info.wildcardProjection = sourceDocument.get("wildcardProjection", Document.class);
+		}
+
 		return info;
 	}
 
@@ -216,6 +223,16 @@ public Optional<Document> getCollation() {
 		return Optional.ofNullable(collation);
 	}
 
+	/**
+	 * Get {@literal wildcardProjection} information.
+	 *
+	 * @return {@link Optional#empty() empty} if not set.
+	 * @since 3.3
+	 */
+	public Optional<Document> getWildcardProjection() {
+		return Optional.ofNullable(wildcardProjection);
+	}
+
 	/**
 	 * Get the duration after which documents within the index expire.
 	 *
@@ -234,6 +251,14 @@ public boolean isHashed() {
 		return getIndexFields().stream().anyMatch(IndexField::isHashed);
 	}
 
+	/**
+	 * @return {@literal true} if a wildcard index field is present.
+	 * @since 3.3
+	 */
+	public boolean isWildcard() {
+		return getIndexFields().stream().anyMatch(IndexField::isWildcard);
+	}
+
 	@Override
 	public String toString() {
 
@@ -303,4 +328,5 @@ public boolean equals(Object obj) {
 		}
 		return true;
 	}
+
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/index/MongoPersistentEntityIndexResolver.java

@@ -46,6 +46,7 @@
 import org.springframework.data.mongodb.core.mapping.Document;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
+import org.springframework.data.mongodb.core.query.Collation;
 import org.springframework.data.mongodb.util.BsonUtils;
 import org.springframework.data.mongodb.util.DotPath;
 import org.springframework.data.spel.EvaluationContextProvider;
@@ -121,6 +122,7 @@ public List<IndexDefinitionHolder> resolveIndexForEntity(MongoPersistentEntity<?
 		List<IndexDefinitionHolder> indexInformation = new ArrayList<>();
 		String collection = root.getCollection();
 		indexInformation.addAll(potentiallyCreateCompoundIndexDefinitions("", collection, root));
+		indexInformation.addAll(potentiallyCreateWildcardIndexDefinitions("", collection, root));
 		indexInformation.addAll(potentiallyCreateTextIndexDefinition(root, collection));
 
 		root.doWithProperties((PropertyHandler<MongoPersistentProperty>) property -> this
@@ -162,17 +164,18 @@ private void potentiallyAddIndexForProperty(MongoPersistentEntity<?> root, Mongo
 	 * @return List of {@link IndexDefinitionHolder} representing indexes for given type and its referenced property
 	 *         types. Will never be {@code null}.
 	 */
-	private List<IndexDefinitionHolder> resolveIndexForClass( TypeInformation<?> type,  String dotPath,
-			 Path path,  String collection,  CycleGuard guard) {
+	private List<IndexDefinitionHolder> resolveIndexForClass(TypeInformation<?> type, String dotPath, Path path,
+			String collection, CycleGuard guard) {
 
 		return resolveIndexForEntity(mappingContext.getRequiredPersistentEntity(type), dotPath, path, collection, guard);
 	}
 
-	private List<IndexDefinitionHolder> resolveIndexForEntity(MongoPersistentEntity<?> entity,  String dotPath,
-			 Path path,  String collection,  CycleGuard guard) {
+	private List<IndexDefinitionHolder> resolveIndexForEntity(MongoPersistentEntity<?> entity, String dotPath, Path path,
+			String collection, CycleGuard guard) {
 
 		List<IndexDefinitionHolder> indexInformation = new ArrayList<>();
 		indexInformation.addAll(potentiallyCreateCompoundIndexDefinitions(dotPath, collection, entity));
+		indexInformation.addAll(potentiallyCreateWildcardIndexDefinitions(dotPath, collection, entity));
 
 		entity.doWithProperties((PropertyHandler<MongoPersistentProperty>) property -> this
 				.guardAndPotentiallyAddIndexForProperty(property, dotPath, path, collection, indexInformation, guard));
@@ -196,15 +199,15 @@ private void guardAndPotentiallyAddIndexForProperty(MongoPersistentProperty pers
 
 		if (persistentProperty.isEntity()) {
 			try {
-				indexes.addAll(resolveIndexForEntity(mappingContext.getPersistentEntity(persistentProperty), propertyDotPath.toString(),
-						propertyPath, collection, guard));
+				indexes.addAll(resolveIndexForEntity(mappingContext.getPersistentEntity(persistentProperty),
+						propertyDotPath.toString(), propertyPath, collection, guard));
 			} catch (CyclicPropertyReferenceException e) {
 				LOGGER.info(e.getMessage());
 			}
 		}
 
-		List<IndexDefinitionHolder> indexDefinitions = createIndexDefinitionHolderForProperty(propertyDotPath.toString(), collection,
-				persistentProperty);
+		List<IndexDefinitionHolder> indexDefinitions = createIndexDefinitionHolderForProperty(propertyDotPath.toString(),
+				collection, persistentProperty);
 
 		if (!indexDefinitions.isEmpty()) {
 			indexes.addAll(indexDefinitions);
@@ -232,6 +235,11 @@ private List<IndexDefinitionHolder> createIndexDefinitionHolderForProperty(Strin
 		if (persistentProperty.isAnnotationPresent(HashIndexed.class)) {
 			indices.add(createHashedIndexDefinition(dotPath, collection, persistentProperty));
 		}
+		if (persistentProperty.isAnnotationPresent(WildcardIndexed.class)) {
+			indices.add(createWildcardIndexDefinition(dotPath, collection,
+					persistentProperty.getRequiredAnnotation(WildcardIndexed.class),
+					mappingContext.getPersistentEntity(persistentProperty)));
+		}
 
 		return indices;
 	}
@@ -246,6 +254,18 @@ private List<IndexDefinitionHolder> potentiallyCreateCompoundIndexDefinitions(St
 		return createCompoundIndexDefinitions(dotPath, collection, entity);
 	}
 
+	private List<IndexDefinitionHolder> potentiallyCreateWildcardIndexDefinitions(String dotPath, String collection,
+			MongoPersistentEntity<?> entity) {
+
+		if (entity.findAnnotation(WildcardIndexed.class) == null) {
+			return Collections.emptyList();
+		}
+
+		return Collections.singletonList(new IndexDefinitionHolder(dotPath,
+				createWildcardIndexDefinition(dotPath, collection, entity.getRequiredAnnotation(WildcardIndexed.class), entity),
+				collection));
+	}
+
 	private Collection<? extends IndexDefinitionHolder> potentiallyCreateTextIndexDefinition(
 			MongoPersistentEntity<?> root, String collection) {
 
@@ -292,9 +312,8 @@ private Collection<? extends IndexDefinitionHolder> potentiallyCreateTextIndexDe
 
 	}
 
-	private void appendTextIndexInformation(DotPath dotPath, Path path,
-			TextIndexDefinitionBuilder indexDefinitionBuilder, MongoPersistentEntity<?> entity,
-			TextIndexIncludeOptions includeOptions, CycleGuard guard) {
+	private void appendTextIndexInformation(DotPath dotPath, Path path, TextIndexDefinitionBuilder indexDefinitionBuilder,
+			MongoPersistentEntity<?> entity, TextIndexIncludeOptions includeOptions, CycleGuard guard) {
 
 		entity.doWithProperties(new PropertyHandler<MongoPersistentProperty>() {
 
@@ -311,8 +330,7 @@ public void doWithPersistentProperty(MongoPersistentProperty persistentProperty)
 
 				if (includeOptions.isForce() || indexed != null || persistentProperty.isEntity()) {
 
-					DotPath propertyDotPath = dotPath
-							.append(persistentProperty.getFieldName());
+					DotPath propertyDotPath = dotPath.append(persistentProperty.getFieldName());
 
 					Path propertyPath = path.append(persistentProperty);
 
@@ -406,6 +424,32 @@ protected IndexDefinitionHolder createCompoundIndexDefinition(String dotPath, St
 		return new IndexDefinitionHolder(dotPath, indexDefinition, collection);
 	}
 
+	protected IndexDefinitionHolder createWildcardIndexDefinition(String dotPath, String collection,
+			WildcardIndexed index, @Nullable MongoPersistentEntity<?> entity) {
+
+		WildcardIndex indexDefinition = new WildcardIndex(dotPath);
+
+		if (StringUtils.hasText(index.wildcardProjection())) {
+			indexDefinition.wildcardProjection(evaluateWildcardProjection(index.wildcardProjection(), entity));
+		}
+
+		if (!index.useGeneratedName()) {
+			indexDefinition.named(pathAwareIndexName(index.name(), dotPath, entity, null));
+		}
+
+		if (StringUtils.hasText(index.partialFilter())) {
+			indexDefinition.partial(evaluatePartialFilter(index.partialFilter(), entity));
+		}
+
+		if (StringUtils.hasText(index.collation())) {
+			indexDefinition.collation(evaluateCollation(index.collation(), entity));
+		} else if (entity != null && entity.hasCollation()) {
+			indexDefinition.collation(entity.getCollation());
+		}
+
+		return new IndexDefinitionHolder(dotPath, indexDefinition, collection);
+	}
+
 	private org.bson.Document resolveCompoundIndexKeyFromStringDefinition(String dotPath, String keyDefinitionString,
 			PersistentEntity<?, ?> entity) {
 
@@ -510,6 +554,33 @@ private PartialIndexFilter evaluatePartialFilter(String filterExpression, Persis
 		return PartialIndexFilter.of(BsonUtils.parse(filterExpression, null));
 	}
 
+	private org.bson.Document evaluateWildcardProjection(String projectionExpression, PersistentEntity<?, ?> entity) {
+
+		Object result = evaluate(projectionExpression, getEvaluationContextForProperty(entity));
+
+		if (result instanceof org.bson.Document) {
+			return (org.bson.Document) result;
+		}
+
+		return BsonUtils.parse(projectionExpression, null);
+	}
+
+	private Collation evaluateCollation(String collationExpression, PersistentEntity<?, ?> entity) {
+
+		Object result = evaluate(collationExpression, getEvaluationContextForProperty(entity));
+		if (result instanceof org.bson.Document) {
+			return Collation.from((org.bson.Document) result);
+		}
+		if (result instanceof Collation) {
+			return (Collation) result;
+		}
+		if (result instanceof String) {
+			return Collation.parse(result.toString());
+		}
+		throw new IllegalStateException("Cannot parse collation " + result);
+
+	}
+
 	/**
 	 * Creates {@link HashedIndex} wrapped in {@link IndexDefinitionHolder} out of {@link HashIndexed} for a given
 	 * {@link MongoPersistentProperty}.
@@ -657,8 +728,8 @@ private void resolveAndAddIndexesForAssociation(Association<MongoPersistentPrope
 							propertyDotPath));
 		}
 
-		List<IndexDefinitionHolder> indexDefinitions = createIndexDefinitionHolderForProperty(propertyDotPath.toString(), collection,
-				property);
+		List<IndexDefinitionHolder> indexDefinitions = createIndexDefinitionHolderForProperty(propertyDotPath.toString(),
+				collection, property);
 
 		if (!indexDefinitions.isEmpty()) {
 			indexes.addAll(indexDefinitions);
@@ -998,6 +1069,11 @@ public org.bson.Document getIndexKeys() {
 		public org.bson.Document getIndexOptions() {
 			return indexDefinition.getIndexOptions();
 		}
+
+		@Override
+		public String toString() {
+			return "IndexDefinitionHolder{" + "indexKeys=" + getIndexKeys() + '}';
+		}
 	}
 
 	/**