Avoid duplicate selection of columns.

pom.xml

@@ -5,7 +5,7 @@
 
 	<groupId>org.springframework.data</groupId>
 	<artifactId>spring-data-relational-parent</artifactId>
-	<version>2.3.0-SNAPSHOT</version>
+	<version>2.3.0-1073-duplicate-select-SNAPSHOT</version>
 	<packaging>pom</packaging>
 
 	<name>Spring Data Relational Parent</name>

spring-data-jdbc-distribution/pom.xml

@@ -14,7 +14,7 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-relational-parent</artifactId>
-		<version>2.3.0-SNAPSHOT</version>
+		<version>2.3.0-1073-duplicate-select-SNAPSHOT</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 

spring-data-jdbc/pom.xml

@@ -6,7 +6,7 @@
 	<modelVersion>4.0.0</modelVersion>
 
 	<artifactId>spring-data-jdbc</artifactId>
-	<version>2.3.0-SNAPSHOT</version>
+	<version>2.3.0-1073-duplicate-select-SNAPSHOT</version>
 
 	<name>Spring Data JDBC</name>
 	<description>Spring Data module for JDBC repositories.</description>
@@ -15,7 +15,7 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-relational-parent</artifactId>
-		<version>2.3.0-SNAPSHOT</version>
+		<version>2.3.0-1073-duplicate-select-SNAPSHOT</version>
 	</parent>
 
 	<properties>

spring-data-jdbc/src/main/java/org/springframework/data/jdbc/core/convert/SqlGenerator.java

@@ -15,6 +15,11 @@
  */
 package org.springframework.data.jdbc.core.convert;
 
+import java.util.*;
+import java.util.function.Function;
+import java.util.regex.Pattern;
+import java.util.stream.Collectors;
+
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.domain.Sort;
 import org.springframework.data.jdbc.repository.support.SimpleJdbcRepository;
@@ -33,11 +38,6 @@
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
-import java.util.*;
-import java.util.function.Function;
-import java.util.regex.Pattern;
-import java.util.stream.Collectors;
-
 /**
  * Generates SQL statements to be used by {@link SimpleJdbcRepository}
  *
@@ -381,11 +381,11 @@ private String createAcquireLockById(LockMode lockMode) {
 		Table table = this.getTable();
 
 		Select select = StatementBuilder //
-			.select(getIdColumn()) //
-			.from(table) //
-			.where(getIdColumn().isEqualTo(getBindMarker(ID_SQL_PARAMETER))) //
-			.lock(lockMode) //
-			.build();
+				.select(getIdColumn()) //
+				.from(table) //
+				.where(getIdColumn().isEqualTo(getBindMarker(ID_SQL_PARAMETER))) //
+				.lock(lockMode) //
+				.build();
 
 		return render(select);
 	}
@@ -395,10 +395,10 @@ private String createAcquireLockAll(LockMode lockMode) {
 		Table table = this.getTable();
 
 		Select select = StatementBuilder //
-			.select(getIdColumn()) //
-			.from(table) //
-			.lock(lockMode) //
-			.build();
+				.select(getIdColumn()) //
+				.from(table) //
+				.lock(lockMode) //
+				.build();
 
 		return render(select);
 	}
@@ -727,9 +727,9 @@ static final class Join {
 
 		Join(Table joinTable, Column joinColumn, Column parentId) {
 
-			Assert.notNull( joinTable,"JoinTable must not be null.");
-			Assert.notNull( joinColumn,"JoinColumn must not be null.");
-			Assert.notNull( parentId,"ParentId must not be null.");
+			Assert.notNull(joinTable, "JoinTable must not be null.");
+			Assert.notNull(joinColumn, "JoinColumn must not be null.");
+			Assert.notNull(parentId, "ParentId must not be null.");
 
 			this.joinTable = joinTable;
 			this.joinColumn = joinColumn;
@@ -751,12 +751,14 @@ Column getParentId() {
 		@Override
 		public boolean equals(Object o) {
 
-			if (this == o) return true;
-			if (o == null || getClass() != o.getClass()) return false;
+			if (this == o) {
+				return true;
+			}
+			if (o == null || getClass() != o.getClass()) {
+				return false;
+			}
 			Join join = (Join) o;
-			return joinTable.equals(join.joinTable) &&
-					joinColumn.equals(join.joinColumn) &&
-					parentId.equals(join.parentId);
+			return joinTable.equals(join.joinTable) && joinColumn.equals(join.joinColumn) && parentId.equals(join.parentId);
 		}
 
 		@Override
@@ -767,10 +769,10 @@ public int hashCode() {
 		@Override
 		public String toString() {
 
-			return "Join{" +
-					"joinTable=" + joinTable +
-					", joinColumn=" + joinColumn +
-					", parentId=" + parentId +
+			return "Join{" + //
+					"joinTable=" + joinTable + //
+					", joinColumn=" + joinColumn + //
+					", parentId=" + parentId + //
 					'}';
 		}
 	}

spring-data-jdbc/src/test/java/org/springframework/data/jdbc/core/convert/SqlGeneratorUnitTests.java

@@ -23,7 +23,6 @@
 import java.util.Map;
 import java.util.Set;
 
-import org.assertj.core.api.SoftAssertions;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.springframework.data.annotation.Id;
@@ -374,6 +373,23 @@ public void findAllByPropertyWithKeyOrdered() {
 				+ "WHERE dummy_entity.backref = :backref " + "ORDER BY key-column");
 	}
 
+	@Test // GH-1073
+	public void findAllByPropertyAvoidsDuplicateColumns() {
+
+		final SqlGenerator sqlGenerator = createSqlGenerator(ReferencedEntity.class);
+		final String sql = sqlGenerator.getFindAllByProperty(
+				Identifier.of(quoted("id"), "parent-id-value", DummyEntity.class), //
+				quoted("X_L1ID"), // this key column collides with the name derived by the naming strategy for the id of
+													// ReferencedEntity.
+				false);
+
+		final String id = "referenced_entity.x_l1id AS x_l1id";
+		assertThat(sql.indexOf(id)) //
+				.describedAs(sql) //
+				.isEqualTo(sql.lastIndexOf(id));
+
+	}
+
 	@Test // DATAJDBC-219
 	public void updateWithVersion() {
 
@@ -709,6 +725,7 @@ static class DummyEntity {
 		Set<Element> elements;
 		Map<Integer, Element> mappedElements;
 		AggregateReference<OtherAggregate, Long> other;
+		Map<Long, ReferencedEntity> mappedReference;
 	}
 
 	static class VersionedEntity extends DummyEntity {

spring-data-relational/pom.xml

@@ -6,15 +6,15 @@
 	<modelVersion>4.0.0</modelVersion>
 
 	<artifactId>spring-data-relational</artifactId>
-	<version>2.3.0-SNAPSHOT</version>
+	<version>2.3.0-1073-duplicate-select-SNAPSHOT</version>
 
 	<name>Spring Data Relational</name>
 	<description>Spring Data Relational support</description>
 
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-relational-parent</artifactId>
-		<version>2.3.0-SNAPSHOT</version>
+		<version>2.3.0-1073-duplicate-select-SNAPSHOT</version>
 	</parent>
 
 	<properties>

spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/AbstractSegment.java

@@ -15,12 +15,15 @@
  */
 package org.springframework.data.relational.core.sql;
 
+import java.util.Arrays;
+
 import org.springframework.util.Assert;
 
 /**
  * Abstract implementation to support {@link Segment} implementations.
  *
  * @author Mark Paluch
+ * @author Jens Schauder
  * @since 1.1
  */
 abstract class AbstractSegment implements Segment {
@@ -47,21 +50,21 @@ public void visit(Visitor visitor) {
 		visitor.leave(this);
 	}
 
-	/*
-	 * (non-Javadoc)
-	 * @see java.lang.Object#hashCode()
-	 */
 	@Override
-	public int hashCode() {
-		return toString().hashCode();
+	public boolean equals(Object o) {
+
+		if (this == o) {
+			return true;
+		}
+		if (o == null || getClass() != o.getClass()) {
+			return false;
+		}
+		AbstractSegment that = (AbstractSegment) o;
+		return Arrays.equals(children, that.children);
 	}
 
-	/*
-	 * (non-Javadoc)
-	 * @see java.lang.Object#equals(java.lang.Object)
-	 */
 	@Override
-	public boolean equals(Object obj) {
-		return obj instanceof Segment && toString().equals(obj.toString());
+	public int hashCode() {
+		return Arrays.hashCode(children);
 	}
 }

spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/Column.java

@@ -15,6 +15,8 @@
  */
 package org.springframework.data.relational.core.sql;
 
+import java.util.Objects;
+
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
@@ -364,6 +366,27 @@ String getPrefix() {
 		return prefix;
 	}
 
+	@Override
+	public boolean equals(Object o) {
+
+		if (this == o) {
+			return true;
+		}
+		if (o == null || getClass() != o.getClass()) {
+			return false;
+		}
+		if (!super.equals(o)) {
+			return false;
+		}
+		Column column = (Column) o;
+		return name.equals(column.name) && table.equals(column.table);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(super.hashCode(), name, table);
+	}
+
 	/**
 	 * {@link Aliased} {@link Column} implementation.
 	 */
@@ -419,5 +442,26 @@ public Column from(Table table) {
 		public String toString() {
 			return getPrefix() + getName() + " AS " + getAlias();
 		}
+
+		@Override
+		public boolean equals(Object o) {
+
+			if (this == o) {
+				return true;
+			}
+			if (o == null || getClass() != o.getClass()) {
+				return false;
+			}
+			if (!super.equals(o)) {
+				return false;
+			}
+			AliasedColumn that = (AliasedColumn) o;
+			return alias.equals(that.alias);
+		}
+
+		@Override
+		public int hashCode() {
+			return Objects.hash(super.hashCode(), alias);
+		}
 	}
 }

spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/Table.java

@@ -15,15 +15,18 @@
  */
 package org.springframework.data.relational.core.sql;
 
+import java.util.Objects;
+
 import org.springframework.util.Assert;
 
 /**
- * Represents a table reference within a SQL statement. Typically used to denote {@code FROM} or {@code JOIN} or to
+ * Represents a table reference within a SQL statement. Typically, used to denote {@code FROM} or {@code JOIN} or to
  * prefix a {@link Column}.
  * <p/>
  * Renders to: {@code <name>} or {@code <name> AS <name>}.
  *
  * @author Mark Paluch
+ * @author Jens Schauder
  * @since 1.1
  */
 public class Table extends AbstractSegment implements TableLike {
@@ -107,7 +110,6 @@ public Table as(SqlIdentifier alias) {
 		return new AliasedTable(name, alias);
 	}
 
-
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.relational.core.sql.Named#getName()
@@ -135,6 +137,26 @@ public String toString() {
 		return name.toString();
 	}
 
+	@Override
+	public boolean equals(Object o) {
+		if (this == o) {
+			return true;
+		}
+		if (o == null || getClass() != o.getClass()) {
+			return false;
+		}
+		if (!super.equals(o)) {
+			return false;
+		}
+		Table table = (Table) o;
+		return name.equals(table.name);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(super.hashCode(), name);
+	}
+
 	/**
 	 * {@link Aliased} {@link Table} implementation.
 	 */
@@ -184,5 +206,26 @@ public SqlIdentifier getReferenceName() {
 		public String toString() {
 			return getName() + " AS " + getAlias();
 		}
+
+		@Override
+		public boolean equals(Object o) {
+
+			if (this == o) {
+				return true;
+			}
+			if (o == null || getClass() != o.getClass()) {
+				return false;
+			}
+			if (!super.equals(o)) {
+				return false;
+			}
+			AliasedTable that = (AliasedTable) o;
+			return alias.equals(that.alias);
+		}
+
+		@Override
+		public int hashCode() {
+			return Objects.hash(super.hashCode(), alias);
+		}
 	}
 }