HHH-14219 Fix duplicated rows of sequence table

if generator is shared by multiple entities

hibernate-core/src/main/java/org/hibernate/id/enhanced/TableStructure.java

@@ -249,8 +249,10 @@ public class TableStructure implements DatabaseStructure {
 		);
 
 		Table table = namespace.locateTable( logicalQualifiedTableName.getObjectName() );
+		boolean tableCreated = false;
 		if ( table == null ) {
 			table = namespace.createTable( logicalQualifiedTableName.getObjectName(), false );
+			tableCreated = true;
 		}
 
 		this.tableNameText = jdbcEnvironment.getQualifiedObjectNameFormatter().format(
@@ -268,17 +270,19 @@ public class TableStructure implements DatabaseStructure {
 		this.updateQuery = "update " + tableNameText +
 				" set " + valueColumnNameText + "= ?" +
 				" where " + valueColumnNameText + "=?";
+		if ( tableCreated ) {
+			ExportableColumn valueColumn = new ExportableColumn(
+					database,
+					table,
+					valueColumnNameText,
+					LongType.INSTANCE
+			);
 
-		ExportableColumn valueColumn = new ExportableColumn(
-				database,
-				table,
-				valueColumnNameText,
-				LongType.INSTANCE
-		);
-		table.addColumn( valueColumn );
+			table.addColumn( valueColumn );
 
-		table.addInitCommand(
-				new InitCommand( "insert into " + tableNameText + " values ( " + initialValue + " )" )
-		);
+			table.addInitCommand(
+					new InitCommand( "insert into " + tableNameText + " values ( " + initialValue + " )" )
+			);
+		}
 	}
 }

hibernate-core/src/test/java/org/hibernate/id/enhanced/HHH14219.java

@@ -0,0 +1,86 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+ * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
+ */
+package org.hibernate.id.enhanced;
+
+import static org.junit.Assert.assertEquals;
+
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+import javax.persistence.MappedSuperclass;
+
+import org.hibernate.Session;
+import org.hibernate.SessionFactory;
+import org.hibernate.boot.Metadata;
+import org.hibernate.boot.MetadataSources;
+import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
+import org.hibernate.dialect.MySQLDialect;
+import org.hibernate.query.Query;
+import org.hibernate.testing.RequiresDialect;
+import org.hibernate.testing.TestForIssue;
+import org.hibernate.testing.junit4.CustomRunner;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+/**
+ * {@inheritDoc}
+ *
+ * @author Yanming Zhou
+ */
+@TestForIssue(jiraKey = "HHH-14219")
+@RunWith(CustomRunner.class)
+@RequiresDialect(MySQLDialect.class)
+public class HHH14219 {
+
+	private SessionFactory sf;
+
+	@Before
+	public void setup() {
+		StandardServiceRegistryBuilder srb = new StandardServiceRegistryBuilder()
+
+				.applySetting("hibernate.show_sql", "true").applySetting("hibernate.format_sql", "true")
+				.applySetting("hibernate.hbm2ddl.auto", "create-drop");
+
+		Metadata metadata = new MetadataSources(srb.build()).addAnnotatedClass(BaseEntity.class)
+				.addAnnotatedClass(Foo.class).addAnnotatedClass(Bar.class).buildMetadata();
+
+		sf = metadata.buildSessionFactory();
+	}
+
+	@Test
+	public void testSequenceTableContainsOnlyOneRow() throws Exception {
+		try (Session session = sf.openSession()) {
+			@SuppressWarnings("unchecked")
+			Query<Number> q = session.createNativeQuery("select count(*) from " + BaseEntity.SHARED_SEQ_NAME);
+			assertEquals(1, q.uniqueResult().intValue());
+		}
+	}
+
+	@MappedSuperclass
+	public static class BaseEntity {
+
+		public static final String SHARED_SEQ_NAME = "shared_seq";
+
+		@Id
+		@GeneratedValue(strategy = GenerationType.AUTO, generator = SHARED_SEQ_NAME)
+		protected Long id;
+
+	}
+
+	@Entity
+	public static class Foo extends BaseEntity {
+
+	}
+
+	@Entity
+	public static class Bar extends BaseEntity {
+
+	}
+
+}