HSEARCH-3909 Allow looking up available predicates/sorts/projections/…

…aggregations for each field in the metamodel

backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/search/predicate/impl/ElasticsearchPredicateTypeKeys.java

@@ -7,19 +7,16 @@
 package org.hibernate.search.backend.elasticsearch.search.predicate.impl;
 
 import org.hibernate.search.backend.elasticsearch.types.predicate.impl.ElasticsearchSimpleQueryStringPredicateBuilderFieldState;
+import org.hibernate.search.engine.backend.types.IndexFieldTraits;
 import org.hibernate.search.engine.search.common.spi.SearchQueryElementTypeKey;
 
 public final class ElasticsearchPredicateTypeKeys {
 
 	private ElasticsearchPredicateTypeKeys() {
 	}
 
-	private static <T> SearchQueryElementTypeKey<T> key(String name) {
-		return SearchQueryElementTypeKey.of( "predicate", name );
-	}
-
 	public static final SearchQueryElementTypeKey<
 			ElasticsearchSimpleQueryStringPredicateBuilderFieldState> SIMPLE_QUERY_STRING =
-					key( "simple-query-string" );
+					SearchQueryElementTypeKey.of( IndexFieldTraits.Predicates.SIMPLE_QUERY_STRING );
 
 }

backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/search/projection/impl/ElasticsearchProjectionTypeKeys.java

@@ -6,7 +6,7 @@
  */
 package org.hibernate.search.backend.elasticsearch.search.projection.impl;
 
-import static org.hibernate.search.engine.search.projection.spi.ProjectionTypeKeys.key;
+import static org.hibernate.search.engine.search.common.spi.SearchQueryElementTypeKey.of;
 
 import org.hibernate.search.engine.search.common.spi.SearchQueryElementTypeKey;
 
@@ -15,8 +15,8 @@ public final class ElasticsearchProjectionTypeKeys {
 	private ElasticsearchProjectionTypeKeys() {
 	}
 
-	public static final SearchQueryElementTypeKey<?> JSON_HIT = key( "json-hit" );
-	public static final SearchQueryElementTypeKey<?> SOURCE = key( "source" );
-	public static final SearchQueryElementTypeKey<?> EXPLANATION = key( "explanation" );
+	public static final SearchQueryElementTypeKey<?> JSON_HIT = of( "projection:json-hit" );
+	public static final SearchQueryElementTypeKey<?> SOURCE = of( "projection:source" );
+	public static final SearchQueryElementTypeKey<?> EXPLANATION = of( "projection:explanation" );
 
 }

backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/types/ElasticsearchIndexFieldTraits.java

@@ -0,0 +1,23 @@
+/*
+ * Hibernate Search, full-text search for your domain model
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later
+ * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
+ */
+package org.hibernate.search.backend.elasticsearch.types;
+
+import org.hibernate.search.engine.backend.types.IndexFieldTraits;
+
+/**
+ * Constants for the names of Elasticsearch-specific traits that can be exposed by index fields.
+ * <p>
+ * Currently empty, because there are no Elasticsearch-specific traits.
+ *
+ * @see IndexFieldTraits
+ */
+public final class ElasticsearchIndexFieldTraits {
+
+	private ElasticsearchIndexFieldTraits() {
+	}
+
+}

backend/lucene/src/main/java/org/hibernate/search/backend/lucene/search/predicate/impl/LucenePredicateTypeKeys.java

@@ -6,16 +6,18 @@
  */
 package org.hibernate.search.backend.lucene.search.predicate.impl;
 
+import static org.hibernate.search.engine.search.common.spi.SearchQueryElementTypeKey.of;
+
 import org.hibernate.search.backend.lucene.types.predicate.impl.LuceneSimpleQueryStringPredicateBuilderFieldState;
+import org.hibernate.search.engine.backend.types.IndexFieldTraits;
 import org.hibernate.search.engine.search.common.spi.SearchQueryElementTypeKey;
-import org.hibernate.search.engine.search.predicate.spi.PredicateTypeKeys;
 
 public final class LucenePredicateTypeKeys {
 
 	private LucenePredicateTypeKeys() {
 	}
 
 	public static final SearchQueryElementTypeKey<LuceneSimpleQueryStringPredicateBuilderFieldState> SIMPLE_QUERY_STRING =
-			PredicateTypeKeys.key( "simple-query-string" );
+			of( IndexFieldTraits.Predicates.SIMPLE_QUERY_STRING );
 
 }

backend/lucene/src/main/java/org/hibernate/search/backend/lucene/search/projection/impl/LuceneProjectionTypeKeys.java

@@ -6,7 +6,7 @@
  */
 package org.hibernate.search.backend.lucene.search.projection.impl;
 
-import static org.hibernate.search.engine.search.projection.spi.ProjectionTypeKeys.key;
+import static org.hibernate.search.engine.search.common.spi.SearchQueryElementTypeKey.of;
 
 import org.hibernate.search.engine.search.common.spi.SearchQueryElementTypeKey;
 
@@ -15,7 +15,7 @@ public final class LuceneProjectionTypeKeys {
 	private LuceneProjectionTypeKeys() {
 	}
 
-	public static final SearchQueryElementTypeKey<?> EXPLANATION = key( "explanation" );
-	public static final SearchQueryElementTypeKey<?> DOCUMENT = key( "document" );
+	public static final SearchQueryElementTypeKey<?> EXPLANATION = of( "projection:explanation" );
+	public static final SearchQueryElementTypeKey<?> DOCUMENT = of( "projection:document" );
 
 }

backend/lucene/src/main/java/org/hibernate/search/backend/lucene/types/LuceneIndexFieldTraits.java

@@ -0,0 +1,24 @@
+/*
+ * Hibernate Search, full-text search for your domain model
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later
+ * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
+ */
+package org.hibernate.search.backend.lucene.types;
+
+import org.hibernate.search.engine.backend.types.IndexFieldTraits;
+
+/**
+ * Constants for the names of Lucene-specific traits that can be exposed by index fields.
+ * <p>
+ * Currently empty, because there are no Lucene-specific traits.
+ *
+ * @see IndexFieldTraits
+ */
+public final class LuceneIndexFieldTraits {
+
+	private LuceneIndexFieldTraits() {
+	}
+
+
+}

documentation/src/main/asciidoc/public/reference/_mapping-inspect.adoc

@@ -48,7 +48,10 @@ is it searchable, sortable, projectable,
 what is the expected java class for arguments to the <<search-dsl,Search DSL>>,
 what are the analyzers/normalizer set on this field,
 ...
-<9> Object fields can also be inspected.
+<9> Inspect the "traits" of a field type:
+each trait represents a predicate/sort/projection/aggregation
+that can be used on fields of that type.
+<10> Object fields can also be inspected.
 ====
 
 [TIP]

documentation/src/test/java/org/hibernate/search/documentation/mapper/orm/indexedentities/SearchMappingIndexedEntitiesIT.java

@@ -7,9 +7,11 @@
 package org.hibernate.search.documentation.mapper.orm.indexedentities;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.fail;
 
 import java.sql.Date;
 import java.util.Optional;
+import java.util.Set;
 
 import jakarta.persistence.EntityManagerFactory;
 
@@ -22,6 +24,7 @@
 import org.hibernate.search.engine.backend.metamodel.IndexObjectFieldTypeDescriptor;
 import org.hibernate.search.engine.backend.metamodel.IndexValueFieldDescriptor;
 import org.hibernate.search.engine.backend.metamodel.IndexValueFieldTypeDescriptor;
+import org.hibernate.search.engine.backend.types.IndexFieldTraits;
 import org.hibernate.search.mapper.orm.Search;
 import org.hibernate.search.mapper.orm.entity.SearchIndexedEntity;
 import org.hibernate.search.mapper.orm.mapping.SearchMapping;
@@ -109,8 +112,26 @@ void indexMetamodel() {
 				assertThat( searchAnalyzerName ).isEmpty();
 				assertThat( normalizerName ).isEmpty();
 				//tag::indexMetamodel[]
+				Set<String> traits = type.traits(); // <9>
+				if ( traits.contains( IndexFieldTraits.Aggregations.RANGE ) ) {
+					// ...
+					//end::indexMetamodel[]
+				}
+				else {
+					fail( "The field should be aggregable!" );
+					//tag::indexMetamodel[]
+				}
+				//end::indexMetamodel[]
+				assertThat( traits ).contains(
+						IndexFieldTraits.Predicates.EXISTS,
+						IndexFieldTraits.Predicates.MATCH,
+						IndexFieldTraits.Predicates.RANGE,
+						IndexFieldTraits.Aggregations.TERMS,
+						IndexFieldTraits.Aggregations.RANGE
+				);
+				//tag::indexMetamodel[]
 			}
-			else if ( field.isObjectField() ) { // <9>
+			else if ( field.isObjectField() ) { // <10>
 				IndexObjectFieldDescriptor objectField = field.toObjectField();
 
 				IndexObjectFieldTypeDescriptor type = objectField.type();

engine/src/main/java/org/hibernate/search/engine/backend/document/model/spi/AbstractIndexField.java

@@ -7,16 +7,16 @@
 package org.hibernate.search.engine.backend.document.model.spi;
 
 import org.hibernate.search.engine.backend.common.spi.FieldPaths;
+import org.hibernate.search.engine.backend.types.spi.AbstractIndexNodeType;
 import org.hibernate.search.engine.common.tree.spi.TreeNodeInclusion;
 import org.hibernate.search.engine.reporting.spi.EventContexts;
-import org.hibernate.search.engine.search.common.spi.SearchIndexNodeTypeContext;
 import org.hibernate.search.engine.search.common.spi.SearchIndexScope;
 import org.hibernate.search.util.common.reporting.EventContext;
 
 public abstract class AbstractIndexField<
 		S extends AbstractIndexField<S, SC, ?, C>,
 		SC extends SearchIndexScope<?>,
-		NT extends SearchIndexNodeTypeContext<SC, ? super S>,
+		NT extends AbstractIndexNodeType<SC, ? super S>,
 		C extends IndexCompositeNode<SC, ?, ?>>
 		extends AbstractIndexNode<S, SC, NT>
 		implements IndexField<SC, C> {

engine/src/main/java/org/hibernate/search/engine/backend/metamodel/IndexFieldDescriptor.java

@@ -38,6 +38,12 @@ public interface IndexFieldDescriptor {
 	 */
 	IndexValueFieldDescriptor toValueField();
 
+	/**
+	 * @return The type of this field, exposing its various capabilities.
+	 * @see IndexFieldTypeDescriptor
+	 */
+	IndexFieldTypeDescriptor type();
+
 	/**
 	 * @return The parent of this field, either the {@link IndexCompositeElementDescriptor#isRoot() index root}
 	 * or an {@link IndexCompositeElementDescriptor#isObjectField() object field}.

engine/src/main/java/org/hibernate/search/engine/backend/metamodel/IndexFieldTypeDescriptor.java

@@ -0,0 +1,30 @@
+/*
+ * Hibernate Search, full-text search for your domain model
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later
+ * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
+ */
+package org.hibernate.search.engine.backend.metamodel;
+
+import java.util.Set;
+
+import org.hibernate.search.engine.backend.types.IndexFieldTraits;
+
+/**
+ * The type of a field in the index,
+ * exposing its various capabilities.
+ *
+ * @see IndexFieldDescriptor#type()
+ * @see IndexValueFieldTypeDescriptor
+ * @see IndexObjectFieldTypeDescriptor
+ */
+public interface IndexFieldTypeDescriptor {
+
+	/**
+	 * @return An (unmodifiable) set of strings
+	 * representing the {@link IndexFieldTraits field traits}
+	 * enabled for fields of this type.
+	 */
+	Set<String> traits();
+
+}

engine/src/main/java/org/hibernate/search/engine/backend/metamodel/IndexObjectFieldTypeDescriptor.java

@@ -14,7 +14,7 @@
  *
  * @see IndexObjectFieldDescriptor
  */
-public interface IndexObjectFieldTypeDescriptor {
+public interface IndexObjectFieldTypeDescriptor extends IndexFieldTypeDescriptor {
 
 	/**
 	 * @return {@code true} if this object field is represented internally as a nested document,

engine/src/main/java/org/hibernate/search/engine/backend/metamodel/IndexValueFieldTypeDescriptor.java

@@ -16,7 +16,7 @@
  *
  * @see IndexValueFieldDescriptor
  */
-public interface IndexValueFieldTypeDescriptor {
+public interface IndexValueFieldTypeDescriptor extends IndexFieldTypeDescriptor {
 
 	/**
 	 * @return {@code true} if search predicates are supported on fields of this type.
@@ -25,7 +25,6 @@ public interface IndexValueFieldTypeDescriptor {
 	 */
 	boolean searchable();
 
-
 	/**
 	 * @return {@code true} if sorts are supported on fields of this type.
 	 * Some sorts may still be unsupported because they don't make sense

engine/src/main/java/org/hibernate/search/engine/backend/types/IndexFieldTraits.java

@@ -0,0 +1,107 @@
+/*
+ * Hibernate Search, full-text search for your domain model
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later
+ * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
+ */
+package org.hibernate.search.engine.backend.types;
+
+/**
+ * Constants for the names of various traits that can be exposed by index fields.
+ * <p>
+ * Traits are a representation of what a field can be used for at search time:
+ * a particular predicate, sort, projections, aggregation...
+ * <p>
+ * See also backend-specific traits: {@code org.hibernate.search.backend.lucene.types.LuceneIndexFieldTraits},
+ * {@code org.hibernate.search.backend.elasticsearch.types.ElasticsearchIndexFieldTraits}.
+ *
+ * @see Predicates
+ * @see Sorts
+ * @see Projections
+ * @see Aggregations
+ */
+public final class IndexFieldTraits {
+
+	private IndexFieldTraits() {
+	}
+
+	/**
+	 * Constants for the names of predicate-related traits that can be exposed by index fields.
+	 *
+	 * @see IndexFieldTraits
+	 */
+	public static class Predicates {
+
+		private Predicates() {
+		}
+
+		public static String named(String name) {
+			return "predicate:named:" + name;
+		}
+
+		public static final String EXISTS = "predicate:exists";
+		public static final String KNN = "predicate:knn";
+		public static final String MATCH = "predicate:match";
+		public static final String NESTED = "predicate:nested";
+		public static final String PHRASE = "predicate:phrase";
+		public static final String RANGE = "predicate:range";
+		public static final String REGEXP = "predicate:regexp";
+		public static final String SIMPLE_QUERY_STRING = "predicate:simple-query-string";
+		public static final String SPATIAL_WITHIN_BOUNDING_BOX = "predicate:spatial:within-bounding-box";
+		public static final String SPATIAL_WITHIN_CIRCLE = "predicate:spatial:within-circle";
+		public static final String SPATIAL_WITHIN_POLYGON = "predicate:spatial:within-polygon";
+		public static final String TERMS = "predicate:terms";
+		public static final String WILDCARD = "predicate:wildcard";
+
+	}
+
+	/**
+	 * Constants for the names of sort-related traits that can be exposed by index fields.
+	 *
+	 * @see IndexFieldTraits
+	 */
+	public static class Sorts {
+
+		private Sorts() {
+		}
+
+		public static final String DISTANCE = "sort:distance";
+		public static final String FIELD = "sort:field";
+
+	}
+
+	/**
+	 * Constants for the names of projection-related traits that can be exposed by index fields.
+	 *
+	 * @see IndexFieldTraits
+	 */
+	public static class Projections {
+
+		private Projections() {
+		}
+
+
+		public static final String DISTANCE = "projection:distance";
+		public static final String FIELD = "projection:field";
+		public static final String HIGHLIGHT = "projection:highlight";
+		public static final String OBJECT = "projection:object";
+
+	}
+
+	/**
+	 * Constants for the names of aggregation-related traits that can be exposed by index fields.
+	 *
+	 * @see IndexFieldTraits
+	 */
+	public static class Aggregations {
+
+		private Aggregations() {
+		}
+
+		public static final String RANGE = "aggregation:range";
+		public static final String TERMS = "aggregation:terms";
+
+	}
+
+
+}