Adds support for dense_vector type

A dense_vector field stores dense vectors of float values. The maximum number of dimensions that can be in a vector should not exceed 2048. A dense_vector field is a single-valued field.

Closes spring-projects#1700

Author: bkimmig

Diff for: src/main/java/org/springframework/data/elasticsearch/annotations/Field.java

@@ -157,14 +157,14 @@
 
 	/**
 	 * if true, the field will be stored in Elasticsearch even if it has a null value
-	 * 
+	 *
 	 * @since 4.1
 	 */
 	boolean storeNullValue() default false;
 
 	/**
 	 * to be used in combination with {@link FieldType#Rank_Feature}
-	 * 
+	 *
 	 * @since 4.1
 	 */
 	boolean positiveScoreImpact() default true;
@@ -185,4 +185,11 @@
 	 * @since 4.1
 	 */
 	NullValueType nullValueType() default NullValueType.String;
+
+	/**
+   	 * to be used in combination with {@link FieldType#Dense_Vector}
+	 *
+	 * @since 4.2
+	 */
+	int dims() default -1;
 }

Diff for: src/main/java/org/springframework/data/elasticsearch/annotations/FieldType.java

@@ -57,5 +57,7 @@ public enum FieldType {
 	/** @since 4.1 */
 	Rank_Features, //
 	/** since 4.2 */
-	Wildcard //
+	Wildcard, //
+  	/** @since 4.2 */
+  	Dense_Vector //
 }

Diff for: src/main/java/org/springframework/data/elasticsearch/annotations/InnerField.java

@@ -140,4 +140,11 @@
 	 * @since 4.1
 	 */
 	NullValueType nullValueType() default NullValueType.String;
+
+    /**
+     * to be used in combination with {@link FieldType#Dense_Vector}
+   	 *
+	 * @since 4.2
+	 */
+	int dims() default -1;
 }

Diff for: src/main/java/org/springframework/data/elasticsearch/core/index/MappingParameters.java

@@ -65,6 +65,7 @@ public final class MappingParameters {
 	static final String FIELD_PARAM_NULL_VALUE = "null_value";
 	static final String FIELD_PARAM_POSITION_INCREMENT_GAP = "position_increment_gap";
 	static final String FIELD_PARAM_POSITIVE_SCORE_IMPACT = "positive_score_impact";
+  	static final String FIELD_PARAM_DIMS = "dims";
 	static final String FIELD_PARAM_SCALING_FACTOR = "scaling_factor";
 	static final String FIELD_PARAM_SEARCH_ANALYZER = "search_analyzer";
 	static final String FIELD_PARAM_STORE = "store";
@@ -94,6 +95,7 @@ public final class MappingParameters {
 	private final NullValueType nullValueType;
 	private final Integer positionIncrementGap;
 	private final boolean positiveScoreImpact;
+  	private final Integer dims;
 	private final String searchAnalyzer;
 	private final double scalingFactor;
 	private final Similarity similarity;
@@ -153,6 +155,8 @@ private MappingParameters(Field field) {
 				|| (maxShingleSize >= 2 && maxShingleSize <= 4), //
 				"maxShingleSize must be in inclusive range from 2 to 4 for field type search_as_you_type");
 		positiveScoreImpact = field.positiveScoreImpact();
+    	dims = field.dims();
+    	Assert.isTrue(dims <= 2048, "The maximum number of dimensions that can be in a vector should not exceed 2048.");
 		Assert.isTrue(field.enabled() || type == FieldType.Object, "enabled false is only allowed for field type object");
 		enabled = field.enabled();
 		eagerGlobalOrdinals = field.eagerGlobalOrdinals();
@@ -191,6 +195,8 @@ private MappingParameters(InnerField field) {
 				|| (maxShingleSize >= 2 && maxShingleSize <= 4), //
 				"maxShingleSize must be in inclusive range from 2 to 4 for field type search_as_you_type");
 		positiveScoreImpact = field.positiveScoreImpact();
+    	dims = field.dims();
+		Assert.isTrue(dims <= 2048, "The maximum number of dimensions that can be in a vector should not exceed 2048.");
 		enabled = true;
 		eagerGlobalOrdinals = field.eagerGlobalOrdinals();
 	}
@@ -323,6 +329,10 @@ public void writeTypeAndParametersTo(XContentBuilder builder) throws IOException
 			builder.field(FIELD_PARAM_POSITIVE_SCORE_IMPACT, positiveScoreImpact);
 		}
 
+    	if (dims >= 1) {
+			builder.field(FIELD_PARAM_DIMS, dims);
+		}
+
 		if (!enabled) {
 			builder.field(FIELD_PARAM_ENABLED, enabled);
 		}

Diff for: src/test/java/org/springframework/data/elasticsearch/core/index/MappingBuilderIntegrationTests.java

@@ -271,6 +271,16 @@ void shouldWriteWildcardFieldMapping() {
 		indexOps.putMapping();
 	}
 
+	@Test // #1700
+	@DisplayName("should write dense_vector field mapping")
+	void shouldWriteDenseVectorFieldMapping() {
+
+		IndexOperations indexOps = operations.indexOps(DenseVectorEntity.class);
+		indexOps.create();
+		indexOps.putMapping();
+		indexOps.delete();
+	}
+
 	@Test // #1370
 	@DisplayName("should write mapping for disabled entity")
 	void shouldWriteMappingForDisabledEntity() {
@@ -657,4 +667,11 @@ static class DisabledMappingProperty {
 		@Field(type = Text) private String text;
 		@Mapping(enabled = false) @Field(type = Object) private Object object;
 	}
+
+	@Data
+	@Document(indexName = "densevector-test")
+	static class DenseVectorEntity {
+		@Id private String id;
+		@Field(type = Dense_Vector, dims = 3) private float[] dense_vector;
+	}
 }

Diff for: src/test/java/org/springframework/data/elasticsearch/core/index/MappingBuilderUnitTests.java

@@ -42,6 +42,7 @@
 
 import org.elasticsearch.search.suggest.completion.context.ContextMapping;
 import org.json.JSONException;
+import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
 import org.springframework.data.annotation.Id;
@@ -506,6 +507,23 @@ void shouldWriteRankFeatureProperties() throws JSONException {
 		assertEquals(expected, mapping, false);
 	}
 
+  	@Test // #1700
+	@DisplayName("should write dense_vector properties")
+	void shouldWriteDenseVectorProperties() throws JSONException {
+		String expected = "{\n" + //
+				"  \"properties\": {\n" + //
+				"    \"my_vector\": {\n" + //
+				"      \"type\": \"dense_vector\",\n" + //
+        		"      \"dims\": 16\n" + //
+				"    }\n" + //
+				"  }\n" + //
+				"}\n"; //
+
+		String mapping = getMappingBuilder().buildPropertyMapping(DenseVectorEntity.class);
+
+		assertEquals(expected, mapping, false);
+	}
+
 	@Test // #1370
 	@DisplayName("should not write mapping when enabled is false on entity")
 	void shouldNotWriteMappingWhenEnabledIsFalseOnEntity() throws JSONException {
@@ -963,6 +981,13 @@ static class RankFeatureEntity {
 		@Field(type = FieldType.Rank_Features) private Map<String, Integer> topics;
 	}
 
+  	@Data
+	static class DenseVectorEntity {
+
+		@Id private String id;
+		@Field(type = FieldType.Dense_Vector, dims = 16) private float[] my_vector;
+	}
+
 	@Data
 	@Mapping(enabled = false)
 	static class DisabledMappingEntity {

Diff for: src/test/java/org/springframework/data/elasticsearch/core/index/MappingParametersTest.java

@@ -1,6 +1,7 @@
 package org.springframework.data.elasticsearch.core.index;
 
 import static org.assertj.core.api.Assertions.*;
+import static org.springframework.data.elasticsearch.annotations.FieldType.Dense_Vector;
 import static org.springframework.data.elasticsearch.annotations.FieldType.Object;
 
 import java.lang.annotation.Annotation;
@@ -66,6 +67,16 @@ void shouldAllowEnabledFalseOnlyOnObjectFields() {
 		assertThatThrownBy(() -> MappingParameters.from(annotation)).isInstanceOf(IllegalArgumentException.class);
 	}
 
+	@Test // #1700
+	@DisplayName("should not allow dims length greater than 2048")
+	void shouldNotAllowDimsLengthGreaterThan2048() {
+		ElasticsearchPersistentEntity<?> failEntity = elasticsearchConverter.get().getMappingContext()
+				.getRequiredPersistentEntity(InvalidDenseVectorClass.class);
+		Annotation annotation = failEntity.getRequiredPersistentProperty("dense_vector").findAnnotation(Field.class);
+
+		assertThatThrownBy(() -> MappingParameters.from(annotation)).isInstanceOf(IllegalArgumentException.class);
+	}
+
 	static class AnnotatedClass {
 		@Nullable @Field private String field;
 		@Nullable @MultiField(mainField = @Field,
@@ -79,4 +90,8 @@ static class AnnotatedClass {
 	static class InvalidEnabledFieldClass {
 		@Nullable @Field(type = FieldType.Text, enabled = false) private String disabledObject;
 	}
+
+	static class InvalidDenseVectorClass {
+		@Field(type = Dense_Vector, dims = 2049) private float[] dense_vector;
+	}
 }