Avoid selection of duplicate columns.

This fixes #1865 for derived queries.

Signed-off-by: Tomasz Bielecki <tomasz.bielecki@gmail.com>

Original pull request #2125
See #1865

spring-data-jdbc/src/main/java/org/springframework/data/jdbc/repository/query/JdbcQueryCreator.java

@@ -16,9 +16,11 @@
 package org.springframework.data.jdbc.repository.query;
 
 import java.util.ArrayList;
+import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Objects;
 import java.util.Optional;
+import java.util.Set;
 
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.domain.Sort;
@@ -60,6 +62,7 @@ import org.springframework.util.Assert;
  * @author Jens Schauder
  * @author Myeonghyeon Lee
  * @author Diego Krupitza
+ * @author Tomasz Bielecki
  * @since 2.0
  */
 class JdbcQueryCreator extends RelationalQueryCreator<ParametrizedQuery> {
@@ -235,7 +238,7 @@ class JdbcQueryCreator extends RelationalQueryCreator<ParametrizedQuery> {
 
 	private SelectBuilder.SelectJoin selectBuilder(Table table) {
 
-		List<Expression> columnExpressions = new ArrayList<>();
+		Set<Expression> columnExpressions = new LinkedHashSet<>();
 		RelationalPersistentEntity<?> entity = entityMetadata.getTableEntity();
 		SqlContext sqlContext = new SqlContext(entity);
 

spring-data-jdbc/src/test/java/org/springframework/data/jdbc/repository/query/PartTreeJdbcQueryUnitTests.java

@@ -39,12 +39,14 @@ import org.springframework.data.jdbc.core.mapping.JdbcMappingContext;
 import org.springframework.data.projection.SpelAwareProxyProjectionFactory;
 import org.springframework.data.relational.core.dialect.Escaper;
 import org.springframework.data.relational.core.dialect.H2Dialect;
+import org.springframework.data.relational.core.mapping.Column;
 import org.springframework.data.relational.core.mapping.Embedded;
 import org.springframework.data.relational.core.mapping.MappedCollection;
 import org.springframework.data.relational.core.mapping.Table;
 import org.springframework.data.relational.core.sql.LockMode;
 import org.springframework.data.relational.repository.Lock;
 import org.springframework.data.relational.repository.query.RelationalParametersParameterAccessor;
+import org.springframework.data.repository.ListCrudRepository;
 import org.springframework.data.repository.NoRepositoryBean;
 import org.springframework.data.repository.Repository;
 import org.springframework.data.repository.core.support.DefaultRepositoryMetadata;
@@ -61,6 +63,7 @@ import org.springframework.jdbc.core.namedparam.NamedParameterJdbcOperations;
  * @author Jens Schauder
  * @author Myeonghyeon Lee
  * @author Diego Krupitza
+ * @author Tomasz Bielecki
  */
 @ExtendWith(MockitoExtension.class)
 public class PartTreeJdbcQueryUnitTests {
@@ -669,6 +672,17 @@ public class PartTreeJdbcQueryUnitTests {
 				.isEqualTo("SELECT COUNT(*) FROM " + TABLE + " WHERE " + TABLE + ".\"FIRST_NAME\" = :first_name");
 	}
 
+	@Test
+	public void mappingMapKeyToChildShouldNotResultInDuplicateColumn() throws Exception {
+		Method method = ParentRepository.class.getMethod("findByName", String.class);
+		var queryMethod = new JdbcQueryMethod(method, new DefaultRepositoryMetadata(ParentRepository.class),
+				new SpelAwareProxyProjectionFactory(), new PropertiesBasedNamedQueries(new Properties()), mappingContext);
+		PartTreeJdbcQuery jdbcQuery = createQuery(queryMethod);
+		ParametrizedQuery query = jdbcQuery.createQuery(getAccessor(queryMethod, new Object[] { "John" }), returnedType);
+
+		assertThat(query.getQuery()).containsOnlyOnce("\"children\".\"NICK_NAME\" AS \"children_NICK_NAME\"");
+	}
+
 	private PartTreeJdbcQuery createQuery(JdbcQueryMethod queryMethod) {
 		return new PartTreeJdbcQuery(mappingContext, queryMethod, JdbcH2Dialect.INSTANCE, converter,
 				mock(NamedParameterJdbcOperations.class), mock(RowMapper.class));
@@ -776,6 +790,19 @@ public class PartTreeJdbcQueryUnitTests {
 		long countByFirstName(String name);
 	}
 
+	@NoRepositoryBean
+	interface ParentRepository extends ListCrudRepository<Parent, Long> {
+		Parent findByName(String name);
+	}
+
+	@Table("parent")
+	record Parent(@Id String name, @MappedCollection(idColumn = "NICK_NAME") Child children) {
+	}
+
+	@Table("children")
+	record Child(@Column("NICK_NAME") String nickName,  String name) {
+	}
+
 	@Table("users")
 	static class User {