#344 - Polishing.

Consider projection properties as SELECT projection. Refactor distinct() into marker method without accepting a boolean flag. Make distinct field final. Update tests.

Original pull request: #346.

src/main/java/org/springframework/data/r2dbc/core/DefaultStatementMapper.java

@@ -86,18 +86,20 @@ class DefaultStatementMapper implements StatementMapper {
 
 		Table table = selectSpec.getTable();
 		SelectBuilder.SelectAndFrom selectAndFrom = StatementBuilder.select(getSelectList(selectSpec, entity));
-		if(selectSpec.isDistinct()){
+
+		if (selectSpec.isDistinct()) {
 			selectAndFrom = selectAndFrom.distinct();
 		}
+
 		SelectBuilder.SelectFromAndJoin selectBuilder = selectAndFrom.from(table);
 
 		BindMarkers bindMarkers = this.dialect.getBindMarkersFactory().create();
 		Bindings bindings = Bindings.empty();
+		CriteriaDefinition criteria = selectSpec.getCriteria();
 
-		if (!selectSpec.getCriteria().isEmpty()) {
+		if (criteria != null && !criteria.isEmpty()) {
 
-			BoundCondition mappedObject = this.updateMapper.getMappedObject(bindMarkers, selectSpec.getCriteria(), table,
-					entity);
+			BoundCondition mappedObject = this.updateMapper.getMappedObject(bindMarkers, criteria, table, entity);
 
 			bindings = mappedObject.getBindings();
 			selectBuilder.where(mappedObject.getCondition());

src/main/java/org/springframework/data/r2dbc/core/StatementMapper.java

@@ -202,7 +202,7 @@ public interface StatementMapper {
 		private final Sort sort;
 		private final long offset;
 		private final int limit;
-		private boolean distinct = false;
+		private final boolean distinct;
 
 		protected SelectSpec(Table table, List<String> projectedFields, List<Expression> selectList,
 				@Nullable CriteriaDefinition criteria, Sort sort, int limit, long offset, boolean distinct) {
@@ -237,8 +237,8 @@ public interface StatementMapper {
 
 			List<String> projectedFields = Collections.emptyList();
 			List<Expression> selectList = Collections.emptyList();
-			return new SelectSpec(Table.create(table), projectedFields, selectList, Criteria.empty(), Sort.unsorted(), -1,
-					-1, false);
+			return new SelectSpec(Table.create(table), projectedFields, selectList, Criteria.empty(), Sort.unsorted(), -1, -1,
+					false);
 		}
 
 		public SelectSpec doWithTable(BiFunction<Table, SelectSpec, SelectSpec> function) {
@@ -279,7 +279,8 @@ public interface StatementMapper {
 			List<Expression> selectList = new ArrayList<>(this.selectList);
 			selectList.addAll(Arrays.asList(expressions));
 
-			return new SelectSpec(this.table, projectedFields, selectList, this.criteria, this.sort, this.limit, this.offset, this.distinct);
+			return new SelectSpec(this.table, projectedFields, selectList, this.criteria, this.sort, this.limit, this.offset,
+					this.distinct);
 		}
 
 		/**
@@ -371,12 +372,11 @@ public interface StatementMapper {
 		/**
 		 * Associate a result statement distinct with the select and create a new {@link SelectSpec}.
 		 *
-		 * @param distinct
 		 * @return the {@link SelectSpec}.
 		 */
-		public SelectSpec distinct(boolean distinct) {
+		public SelectSpec distinct() {
 			return new SelectSpec(this.table, this.projectedFields, this.selectList, this.criteria, this.sort, limit,
-					this.offset, distinct);
+					this.offset, true);
 		}
 
 		public Table getTable() {

src/main/java/org/springframework/data/r2dbc/repository/query/PartTreeR2dbcQuery.java

@@ -15,6 +15,10 @@
  */
 package org.springframework.data.r2dbc.repository.query;
 
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
 import org.springframework.data.domain.Sort;
 import org.springframework.data.r2dbc.convert.R2dbcConverter;
 import org.springframework.data.r2dbc.core.DatabaseClient;
@@ -23,6 +27,8 @@ import org.springframework.data.r2dbc.core.ReactiveDataAccessStrategy;
 import org.springframework.data.relational.repository.query.RelationalEntityMetadata;
 import org.springframework.data.relational.repository.query.RelationalParameterAccessor;
 import org.springframework.data.relational.repository.query.RelationalParameters;
+import org.springframework.data.repository.query.ResultProcessor;
+import org.springframework.data.repository.query.ReturnedType;
 import org.springframework.data.repository.query.parser.PartTree;
 
 /**
@@ -34,6 +40,7 @@ import org.springframework.data.repository.query.parser.PartTree;
  */
 public class PartTreeR2dbcQuery extends AbstractR2dbcQuery {
 
+	private final ResultProcessor processor;
 	private final ReactiveDataAccessStrategy dataAccessStrategy;
 	private final RelationalParameters parameters;
 	private final PartTree tree;
@@ -50,6 +57,8 @@ public class PartTreeR2dbcQuery extends AbstractR2dbcQuery {
 	public PartTreeR2dbcQuery(R2dbcQueryMethod method, DatabaseClient databaseClient, R2dbcConverter converter,
 			ReactiveDataAccessStrategy dataAccessStrategy) {
 		super(method, databaseClient, converter);
+
+		this.processor = method.getResultProcessor();
 		this.dataAccessStrategy = dataAccessStrategy;
 		this.parameters = method.getParameters();
 
@@ -78,8 +87,16 @@ public class PartTreeR2dbcQuery extends AbstractR2dbcQuery {
 	@Override
 	protected BindableQuery createQuery(RelationalParameterAccessor accessor) {
 
+		ReturnedType returnedType = processor.withDynamicProjection(accessor).getReturnedType();
+		List<String> projectedProperties = Collections.emptyList();
+
+		if (returnedType.needsCustomConstruction()) {
+			projectedProperties = new ArrayList<>(returnedType.getInputProperties());
+		}
+
 		RelationalEntityMetadata<?> entityMetadata = getQueryMethod().getEntityInformation();
-		R2dbcQueryCreator queryCreator = new R2dbcQueryCreator(tree, dataAccessStrategy, entityMetadata, accessor);
+		R2dbcQueryCreator queryCreator = new R2dbcQueryCreator(tree, dataAccessStrategy, entityMetadata, accessor,
+				projectedProperties);
 		PreparedOperation<?> preparedQuery = queryCreator.createQuery(getDynamicSort(accessor));
 
 		return new PreparedOperationBindableQuery(preparedQuery);

src/main/java/org/springframework/data/r2dbc/repository/query/R2dbcQueryCreator.java

@@ -15,6 +15,7 @@
  */
 package org.springframework.data.r2dbc.repository.query;
 
+import java.util.ArrayList;
 import java.util.List;
 import java.util.stream.Collectors;
 
@@ -32,7 +33,7 @@ import org.springframework.data.relational.repository.query.RelationalParameterA
 import org.springframework.data.relational.repository.query.RelationalQueryCreator;
 import org.springframework.data.repository.query.parser.AbstractQueryCreator;
 import org.springframework.data.repository.query.parser.PartTree;
-import org.springframework.util.Assert;
+import org.springframework.lang.Nullable;
 
 /**
  * Implementation of {@link AbstractQueryCreator} that creates {@link PreparedOperation} from a {@link PartTree}.
@@ -42,34 +43,35 @@ import org.springframework.util.Assert;
  * @author Mingyuan Wu
  * @since 1.1
  */
-public class R2dbcQueryCreator extends RelationalQueryCreator<PreparedOperation<?>> {
+class R2dbcQueryCreator extends RelationalQueryCreator<PreparedOperation<?>> {
 
 	private final PartTree tree;
 	private final RelationalParameterAccessor accessor;
 	private final ReactiveDataAccessStrategy dataAccessStrategy;
 	private final RelationalEntityMetadata<?> entityMetadata;
+	private final List<String> projectedProperties;
 
 	/**
 	 * Creates new instance of this class with the given {@link PartTree}, {@link ReactiveDataAccessStrategy},
 	 * {@link RelationalEntityMetadata} and {@link RelationalParameterAccessor}.
-	 *
+	 * 
 	 * @param tree part tree, must not be {@literal null}.
 	 * @param dataAccessStrategy data access strategy, must not be {@literal null}.
 	 * @param entityMetadata relational entity metadata, must not be {@literal null}.
 	 * @param accessor parameter metadata provider, must not be {@literal null}.
+	 * @param projectedProperties properties to project, must not be {@literal null}.
 	 */
 	public R2dbcQueryCreator(PartTree tree, ReactiveDataAccessStrategy dataAccessStrategy,
-			RelationalEntityMetadata<?> entityMetadata, RelationalParameterAccessor accessor) {
+			RelationalEntityMetadata<?> entityMetadata, RelationalParameterAccessor accessor,
+			List<String> projectedProperties) {
 		super(tree, accessor);
 
-		Assert.notNull(dataAccessStrategy, "Data access strategy must not be null");
-		Assert.notNull(entityMetadata, "Relational entity metadata must not be null");
-
 		this.tree = tree;
 		this.accessor = accessor;
 
 		this.dataAccessStrategy = dataAccessStrategy;
 		this.entityMetadata = entityMetadata;
+		this.projectedProperties = projectedProperties;
 	}
 
 	/**
@@ -80,7 +82,7 @@ public class R2dbcQueryCreator extends RelationalQueryCreator<PreparedOperation<
 	 * @return instance of {@link PreparedOperation}
 	 */
 	@Override
-	protected PreparedOperation<?> complete(Criteria criteria, Sort sort) {
+	protected PreparedOperation<?> complete(@Nullable Criteria criteria, Sort sort) {
 
 		StatementMapper statementMapper = dataAccessStrategy.getStatementMapper().forType(entityMetadata.getJavaType());
 
@@ -91,7 +93,7 @@ public class R2dbcQueryCreator extends RelationalQueryCreator<PreparedOperation<
 		return select(criteria, sort, statementMapper);
 	}
 
-	private PreparedOperation<?> delete(Criteria criteria, StatementMapper statementMapper) {
+	private PreparedOperation<?> delete(@Nullable Criteria criteria, StatementMapper statementMapper) {
 
 		StatementMapper.DeleteSpec deleteSpec = statementMapper.createDelete(entityMetadata.getTableName())
 				.withCriteria(criteria);
@@ -99,7 +101,7 @@ public class R2dbcQueryCreator extends RelationalQueryCreator<PreparedOperation<
 		return statementMapper.getMappedObject(deleteSpec);
 	}
 
-	private PreparedOperation<?> select(Criteria criteria, Sort sort, StatementMapper statementMapper) {
+	private PreparedOperation<?> select(@Nullable Criteria criteria, Sort sort, StatementMapper statementMapper) {
 
 		StatementMapper.SelectSpec selectSpec = statementMapper.createSelect(entityMetadata.getTableName())
 				.withProjection(getSelectProjection());
@@ -123,8 +125,8 @@ public class R2dbcQueryCreator extends RelationalQueryCreator<PreparedOperation<
 			selectSpec = selectSpec.withSort(getSort(sort));
 		}
 
-		if(tree.isDistinct()){
-			selectSpec = selectSpec.distinct(true);
+		if (tree.isDistinct()) {
+			selectSpec = selectSpec.distinct();
 		}
 
 		return statementMapper.getMappedObject(selectSpec);
@@ -134,7 +136,18 @@ public class R2dbcQueryCreator extends RelationalQueryCreator<PreparedOperation<
 
 		List<SqlIdentifier> columnNames;
 
-		if (tree.isExistsProjection()) {
+		if (!projectedProperties.isEmpty()) {
+
+			RelationalPersistentEntity<?> entity = entityMetadata.getTableEntity();
+			columnNames = new ArrayList<>(projectedProperties.size());
+
+			for (String projectedProperty : projectedProperties) {
+
+				RelationalPersistentProperty property = entity.getPersistentProperty(projectedProperty);
+				columnNames.add(property != null ? property.getColumnName() : SqlIdentifier.unquoted(projectedProperty));
+			}
+
+		} else if (tree.isExistsProjection()) {
 			columnNames = dataAccessStrategy.getIdentifierColumns(entityMetadata.getJavaType());
 		} else {
 			columnNames = dataAccessStrategy.getAllColumns(entityMetadata.getJavaType());

src/test/java/org/springframework/data/r2dbc/repository/AbstractR2dbcRepositoryIntegrationTests.java

@@ -156,6 +156,26 @@ public abstract class AbstractR2dbcRepositoryIntegrationTests extends R2dbcInteg
 				}).verifyComplete();
 	}
 
+	@Test // gh-344
+	public void shouldFindApplyingDistinctProjection() {
+
+		LegoSet legoSet1 = new LegoSet(null, "SCHAUFELRADBAGGER", 12);
+		LegoSet legoSet2 = new LegoSet(null, "SCHAUFELRADBAGGER", 13);
+
+		repository.saveAll(Arrays.asList(legoSet1, legoSet2)) //
+				.as(StepVerifier::create) //
+				.expectNextCount(2) //
+				.verifyComplete();
+
+		repository.findDistinctBy() //
+				.map(Named::getName) //
+				.collectList() //
+				.as(StepVerifier::create) //
+				.consumeNextWith(actual -> {
+					assertThat(actual).hasSize(1).contains("SCHAUFELRADBAGGER");
+				}).verifyComplete();
+	}
+
 	@Test // gh-41
 	public void shouldFindApplyingSimpleTypeProjection() {
 
@@ -282,6 +302,8 @@ public abstract class AbstractR2dbcRepositoryIntegrationTests extends R2dbcInteg
 
 		Flux<Named> findAsProjection();
 
+		Flux<Named> findDistinctBy();
+
 		Mono<LegoSet> findByManual(int manual);
 
 		Flux<Integer> findAllIds();

src/test/java/org/springframework/data/r2dbc/repository/query/PartTreeR2dbcQueryUnitTests.java

@@ -614,11 +614,10 @@ public class PartTreeR2dbcQueryUnitTests {
 				dataAccessStrategy);
 		BindableQuery bindableQuery = r2dbcQuery.createQuery(getAccessor(queryMethod, new Object[] { "John" }));
 
-		assertThat(bindableQuery.get())
-				.isEqualTo("SELECT " + DISTINCT + " " + ALL_FIELDS + " FROM " + TABLE + " WHERE " + TABLE + ".first_name = $1");
+		assertThat(bindableQuery.get()).isEqualTo("SELECT " + DISTINCT + " " + TABLE + ".first_name, " + TABLE
+				+ ".foo FROM " + TABLE + " WHERE " + TABLE + ".first_name = $1");
 	}
 
-
 	private R2dbcQueryMethod getQueryMethod(String methodName, Class<?>... parameterTypes) throws Exception {
 		Method method = UserRepository.class.getMethod(methodName, parameterTypes);
 		return new R2dbcQueryMethod(method, new DefaultRepositoryMetadata(UserRepository.class),
@@ -696,8 +695,8 @@ public class PartTreeR2dbcQueryUnitTests {
 		Flux<User> findTop3ByFirstName(String firstName);
 
 		Mono<User> findFirstByFirstName(String firstName);
-		
-		Mono<User> findDistinctByFirstName(String firstName);
+
+		Mono<UserProjection> findDistinctByFirstName(String firstName);
 
 		Mono<Integer> deleteByFirstName(String firstName);
 	}
@@ -713,4 +712,11 @@ public class PartTreeR2dbcQueryUnitTests {
 		private Integer age;
 		private Boolean active;
 	}
+
+	interface UserProjection {
+
+		String getFirstName();
+
+		String getFoo();
+	}
 }