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I recently stumbled upon a possible bug with the discriminator column in an inheritance hierarchy.
You can find the appropiate test case here: https://github.com/shiruba/hibernate-discriminatorvalue-test
Suppose I got the following inheritance hierarchy:
@Entity
@Inheritance(strategy = InheritanceType.JOINED)
@DiscriminatorColumn
public class Parent {}
@Entity
public class SpecialParent extends Parent {}
@Entity
public class VerySpecialParent extends SpecialParent {}
If I try to persist an instance of SpecialParent, I get the following stacktrace:
INFO: HHH000327: Error performing load command : org.hibernate.exception.SQLGrammarException: could not extract ResultSet
javax.persistence.PersistenceException: org.hibernate.exception.SQLGrammarException: could not extract ResultSet
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1763)
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1677)
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1683)
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.merge(AbstractEntityManagerImpl.java:1206)
at de.codecentric.hibernate.DiscriminatorColumnTest.testDiscriminatorValueInInheritanceWithConcreteType(DiscriminatorColumnTest.java:22)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:74)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:211)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:67)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)
Caused by: org.hibernate.exception.SQLGrammarException: could not extract ResultSet
at org.hibernate.exception.internal.SQLExceptionTypeDelegate.convert(SQLExceptionTypeDelegate.java:80)
at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:49)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:126)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:112)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:91)
at org.hibernate.loader.Loader.getResultSet(Loader.java:2065)
at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1862)
at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1838)
at org.hibernate.loader.Loader.doQuery(Loader.java:909)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:354)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:324)
at org.hibernate.loader.Loader.loadEntity(Loader.java:2148)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:78)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:68)
at org.hibernate.persister.entity.AbstractEntityPersister.load(AbstractEntityPersister.java:4126)
at org.hibernate.event.internal.DefaultLoadEventListener.loadFromDatasource(DefaultLoadEventListener.java:503)
at org.hibernate.event.internal.DefaultLoadEventListener.doLoad(DefaultLoadEventListener.java:468)
at org.hibernate.event.internal.DefaultLoadEventListener.load(DefaultLoadEventListener.java:213)
at org.hibernate.event.internal.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:275)
at org.hibernate.event.internal.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:151)
at org.hibernate.internal.SessionImpl.fireLoad(SessionImpl.java:1070)
at org.hibernate.internal.SessionImpl.access$2000(SessionImpl.java:176)
at org.hibernate.internal.SessionImpl$IdentifierLoadAccessImpl.load(SessionImpl.java:2551)
at org.hibernate.internal.SessionImpl.get(SessionImpl.java:960)
at org.hibernate.event.internal.DefaultMergeEventListener.entityIsDetached(DefaultMergeEventListener.java:306)
at org.hibernate.event.internal.DefaultMergeEventListener.onMerge(DefaultMergeEventListener.java:186)
at org.hibernate.event.internal.DefaultMergeEventListener.onMerge(DefaultMergeEventListener.java:85)
at org.hibernate.internal.SessionImpl.fireMerge(SessionImpl.java:876)
at org.hibernate.internal.SessionImpl.merge(SessionImpl.java:858)
at org.hibernate.internal.SessionImpl.merge(SessionImpl.java:863)
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.merge(AbstractEntityManagerImpl.java:1196)
... 27 more
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown column 'specialpar0_.DTYPE' in 'field list'
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:408)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:408)
at com.mysql.jdbc.Util.getInstance(Util.java:383)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1062)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4226)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4158)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2615)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2776)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2840)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2082)
at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:2212)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:82)
... 53 more
If I remove the @DiscriminatorColumn annotation at Parent, everything works fine. This led me to reading the spec and paragraph 11.1.12, which I understand as follows:
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The @DiscriminatorColumn annotation is optional for the SINGLE_TABLE and JOINED inheritance strategies.
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In case no @DiscriminatorColumn is specified, the discriminator column name defaults to DTYPE and the type to STRING.
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A @DiscriminatorColumn has to be specified at the root of the inheritance hierarchy.
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A @DiscriminatorColumn can be used in a subhierarchy in which a different inheritance strategy shall be applied.
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A @DiscriminatorValue will be generated, if none was provided.
Obviously, Hibernate expects the discriminator column to be somewhere else, but not on the direct super class.
This leads to my question: Is this a bug OR is this a configuration issue (in which case Hibernate should not generate invalid SQL but throw an exception of some kind)?
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