Support derived queries from methods named findDistinctF1AndF2ByF3()

src/main/java/org/springframework/data/couchbase/core/ReactiveFindByQueryOperationSupport.java

@@ -176,7 +176,7 @@ public Flux<T> all() {
 			}).flatMapMany(ReactiveQueryResult::rowsAsObject).flatMap(row -> {
 				String id = "";
 				long cas = 0;
-				if (distinctFields == null) {
+				if (!query.isDistinct() && distinctFields == null) {
 					if (row.getString(TemplateUtils.SELECT_ID) == null) {
 						return Flux.error(new CouchbaseException(
 								"query did not project " + TemplateUtils.SELECT_ID + ". Either use #{#n1ql.selectEntity} or project "
@@ -227,7 +227,8 @@ public Mono<Boolean> exists() {
 		}
 
 		private String assembleEntityQuery(final boolean count, String[] distinctFields, String collection) {
-			return query.toN1qlSelectString(template, collection, this.domainType, this.returnType, count, distinctFields);
+			return query.toN1qlSelectString(template, collection, this.domainType, this.returnType, count,
+					query.getDistinctFields() != null ? query.getDistinctFields() : distinctFields);
 		}
 	}
 }

src/main/java/org/springframework/data/couchbase/core/query/Query.java

@@ -51,6 +51,8 @@ public class Query {
 	private JsonValue parameters = JsonValue.ja();
 	private long skip;
 	private int limit;
+	private boolean distinct;
+	private String[] distinctFields;
 	private Sort sort = Sort.unsorted();
 	private QueryScanConsistency queryScanConsistency;
 	private Meta meta;
@@ -123,6 +125,46 @@ public Query limit(int limit) {
 		return this;
 	}
 
+	/**
+	 * Is this a DISTINCT query? {@code distinct}.
+	 *
+	 * @param distinct
+	 * @return
+	 */
+	public Query distinct(boolean distinct) {
+		this.distinct = distinct;
+		return this;
+	}
+
+	/**
+	 * Is this a DISTINCT query? {@code distinct}.
+	 *
+	 * @return distinct
+	 */
+	public boolean isDistinct() {
+		return distinct;
+	}
+
+	/**
+	 * distinctFields for query (non-null but empty means all fields) ? {@code distinctFields}.
+	 *
+	 * @param distinctFields
+	 * @return
+	 */
+	public Query distinct(String[] distinctFields) {
+		this.distinctFields = distinctFields;
+		return this;
+	}
+
+	/**
+	 * distinctFields for query (non-null but empty means all fields) ? {@code distinctFields}.
+	 *
+	 * @return distinctFields
+	 */
+	public String[] getDistinctFields() {
+		return distinctFields;
+	}
+
 	/**
 	 * Sets the given pagination information on the {@link Query} instance. Will transparently set {@code skip} and
 	 * {@code limit} as well as applying the {@link Sort} instance defined with the {@link Pageable}.

src/main/java/org/springframework/data/couchbase/repository/query/CouchbasePartTree.java

@@ -0,0 +1,64 @@
+/*
+ * Copyright 2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.data.couchbase.repository.query;
+
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import org.springframework.data.mapping.PropertyPath;
+import org.springframework.data.repository.query.parser.Part;
+import org.springframework.data.repository.query.parser.PartTree;
+
+/**
+ * Extend PartTree to parse out distinct fields
+ *
+ * @author Michael Reiche
+ */
+public class CouchbasePartTree extends PartTree {
+	private static final Pattern DISTINCT_TEMPLATE = Pattern
+			.compile("^(find|read|get|query|search|stream|count)(Distinct)(\\p{Lu}.*?)(First|Top|By|$)");
+
+	String[] distinctFields;
+
+	public CouchbasePartTree(String methodName, Class<?> domainType) {
+		super(methodName, domainType);
+		maybeInitDistinctFields(methodName, domainType);
+	}
+
+	String[] getDistinctFields() {
+		return distinctFields;
+	}
+
+	private void maybeInitDistinctFields(String methodName, Class<?> domainType) {
+		if (isDistinct()) {
+			Matcher grp = DISTINCT_TEMPLATE.matcher(methodName);
+			if (grp.matches()) {
+				String grp3 = grp.group(3);
+				String[] names = grp.group(3).split("And");
+				int parameterCount = names.length;
+				distinctFields = new String[names.length];
+				for (int i = 0; i < parameterCount; ++i) {
+					Part.Type type = Part.Type.fromProperty(names[i]);
+					PropertyPath path = PropertyPath.from(type.extractProperty(names[i]), domainType);
+					distinctFields[i] = path.toDotPath();
+				}
+			} else {
+				distinctFields = new String[0];
+			}
+		}
+	}
+}

src/main/java/org/springframework/data/couchbase/repository/query/N1qlQueryCreator.java

@@ -39,7 +39,6 @@
 import org.springframework.data.repository.query.parser.AbstractQueryCreator;
 import org.springframework.data.repository.query.parser.Part;
 import org.springframework.data.repository.query.parser.PartTree;
-import org.springframework.util.Assert;
 
 /**
  * @author Michael Nitschinger
@@ -52,6 +51,7 @@ public class N1qlQueryCreator extends AbstractQueryCreator<Query, QueryCriteria>
 	public static final String META_CAS_PROPERTY = "cas";
 	public static final String META_EXPIRATION_PROPERTY = "expiration";
 
+	private final PartTree tree;
 	private final ParameterAccessor accessor;
 	private final MappingContext<?, CouchbasePersistentProperty> context;
 	private final QueryMethod queryMethod;
@@ -61,6 +61,7 @@ public class N1qlQueryCreator extends AbstractQueryCreator<Query, QueryCriteria>
 	public N1qlQueryCreator(final PartTree tree, final ParameterAccessor accessor, final QueryMethod queryMethod,
 			final CouchbaseConverter converter, final String bucketName) {
 		super(tree, accessor);
+		this.tree = tree;
 		this.accessor = accessor;
 		this.context = converter.getMappingContext();
 		this.queryMethod = queryMethod;
@@ -79,10 +80,11 @@ protected QueryCriteria create(final Part part, final Iterator<Object> iterator)
 	public Query createQuery() {
 		Query q = this.createQuery((Optional.of(this.accessor).map(ParameterAccessor::getSort).orElse(Sort.unsorted())));
 		Pageable pageable = accessor.getPageable();
-		if(pageable.isPaged()) {
+		if (pageable.isPaged()) {
 			q.skip(pageable.getOffset());
 			q.limit(pageable.getPageSize());
 		}
+		q.distinct(tree.isDistinct());
 		return q;
 	}
 

src/main/java/org/springframework/data/couchbase/repository/query/PartTreeCouchbaseQuery.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2020 the original author or authors.
+ * Copyright 2020-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -35,7 +35,7 @@
  */
 public class PartTreeCouchbaseQuery extends AbstractCouchbaseQuery {
 
-	private final PartTree tree;
+	private final CouchbasePartTree tree;
 	private final CouchbaseConverter converter;
 
 	/**
@@ -52,7 +52,7 @@ public PartTreeCouchbaseQuery(CouchbaseQueryMethod method, CouchbaseOperations o
 		super(method, operations, expressionParser, evaluationContextProvider);
 
 		ResultProcessor processor = method.getResultProcessor();
-		this.tree = new PartTree(method.getName(), processor.getReturnedType().getDomainType());
+		this.tree = new CouchbasePartTree(method.getName(), processor.getReturnedType().getDomainType());
 		this.converter = operations.getConverter();
 	}
 
@@ -79,6 +79,9 @@ protected Query createQuery(ParametersParameterAccessor accessor) {
 		if (tree.isLimiting()) {
 			query.limit(tree.getMaxResults());
 		}
+		if (tree.isDistinct()) {
+			query.distinct(tree.getDistinctFields());
+		}
 		return query;
 
 	}
@@ -128,4 +131,5 @@ protected boolean isDeleteQuery() {
 	protected boolean isLimiting() {
 		return tree.isLimiting();
 	}
+
 }

src/test/java/org/springframework/data/couchbase/domain/AirportRepository.java

@@ -130,6 +130,18 @@ Long countFancyExpression(@Param("projectIds") List<String> projectIds, @Param("
 	@ScanConsistency(query = QueryScanConsistency.REQUEST_PLUS)
 	Optional<Airport> findByIdAndIata(String id, String iata);
 
+	@ScanConsistency(query = QueryScanConsistency.REQUEST_PLUS)
+	List<Airport> findDistinctIcaoBy();
+
+	@ScanConsistency(query = QueryScanConsistency.REQUEST_PLUS)
+	List<Airport> findDistinctIcaoAndIataBy();
+
+	@ScanConsistency(query = QueryScanConsistency.REQUEST_PLUS)
+	Long countDistinctIcaoAndIataBy();
+
+	@ScanConsistency(query = QueryScanConsistency.REQUEST_PLUS)
+	Long countDistinctIcaoBy();
+
 	@Query("SELECT 1 FROM `#{#n1ql.bucket}` WHERE #{#n1ql.filter} " + " #{#projectIds != null ? 'AND blah IN $1' : ''} "
 			+ " #{#planIds != null ? 'AND blahblah IN $2' : ''} " + " #{#active != null ? 'AND false = $3' : ''} ")
 	Long countOne();

src/test/java/org/springframework/data/couchbase/repository/CouchbaseRepositoryQueryIntegrationTests.java

@@ -533,6 +533,38 @@ void threadSafeParametersTest() throws Exception {
 		}
 	}
 
+	@Test
+	void distinct() {
+		String[] iatas = { "JFK", "IAD", "SFO", "SJC", "SEA", "LAX", "PHX" };
+		String[] icaos = { "ic0", "ic1", "ic0", "ic1", "ic0", "ic1", "ic0" };
+
+		try {
+			for (int i = 0; i < iatas.length; i++) {
+				Airport airport = new Airport("airports::" + iatas[i], iatas[i] /*iata*/, icaos[i] /* icao */);
+				couchbaseTemplate.insertById(Airport.class).one(airport);
+			}
+
+			// distinct icao - parser requires 'By' on the end or it does not match pattern.
+			List<Airport> airports1 = airportRepository.findDistinctIcaoBy();
+			assertEquals(2, airports1.size());
+
+			List<Airport> airports2 = airportRepository.findDistinctIcaoAndIataBy();
+			assertEquals(7, airports2.size());
+
+			// count( distinct { iata, icao } )
+			long count1 = airportRepository.countDistinctIcaoAndIataBy();
+			assertEquals(7, count1);
+
+			// count( distinct { icao } )
+			long count2 = airportRepository.countDistinctIcaoBy();
+			assertEquals(2, count2);
+
+		} finally {
+			couchbaseTemplate.removeById()
+					.all(Arrays.stream(iatas).map((iata) -> "airports::" + iata).collect(Collectors.toSet()));
+		}
+	}
+
 	@Test
 	void stringQueryTest() throws Exception {
 		Airport airport = new Airport("airports::vie", "vie", "lowx");