title: Not able to Save records using JPA table per sub class strategy
body: <p>I have one parent entity and two child entities.
  ReportDetails is my parent entity and ReportBarChart and ReportPieChart are my child entities. The above three share some common fields.
  So to while saving the details I'm using table per sub class strategy in JPA.
  But after setting the Parent entity values, while persisting the entity getting following error.</p>
  
  <pre><code> INFO  [stdout] (default task-66) Hibernate: select OVIMPLWZ.OV_RPT_SEQ.nextval from dummy
  
  INFO  [stdout] (default task-66) Hibernate: insert into OVIMPLWZ.OV_RPT (AUDIT_CRT_DATE, CHART_TYPE, CRT_USER, DSBRD_LINK, KPI_MASTER_KEY, PLANT_KEY, PUBLSH_FLDR, PUBLSH_IND, RPT_DESC, RPT_NAME, TNT_KEY, UPD_USER, RPT_KEY) values (?, 79, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
  
  INFO  [org.hibernate.engine.jdbc.batch.internal.AbstractBatchImpl] (default task-66) HHH000010: On release of batch it still contained JDBC statements
  WARN  [org.hibernate.engine.jdbc.spi.SqlExceptionHelper] (default task-66) SQL Error: -11252, SQLState: HY009
  ERROR [org.hibernate.engine.jdbc.spi.SqlExceptionHelper] (default task-66) SAP DBTech JDBC: Column index 13 was not found.
  WARN  [com.arjuna.ats.arjuna] (default task-66) ARJUNA012125: TwoPhaseCoordinator.beforeCompletion - failed for SynchronizationImple&lt; 0:ffffac103470:-51bf6313:563b07bd:e3b, org.hibernate.engine.transaction.synchronization.internal.RegisteredSynchronization@192b3dcb &gt;: javax.persistence.PersistenceException: org.hibernate.exception.GenericJDBCException: could not insert: [com.rolta.oneviewmr.model.ReportPieChart]
  </code></pre>
  
  <p>My entities are </p>
  
  <p>ReportDetails.java</p>
  
  <pre><code>@Entity
  @Table(name="OV_RPT")
  @Inheritance(strategy=InheritanceType.JOINED)  
  @DiscriminatorColumn(name="CHART_TYPE",
  discriminatorType=DiscriminatorType.INTEGER)  
  @SequenceGenerator(name="OV_RPT_SEQ",sequenceName="OV_RPT_SEQ",
  allocationSize=1)
  public class ReportDetails extends ModelObject{
  
  /**
   * 
   */
  private static final long serialVersionUID = 1L;
  @Id
  @GeneratedValue(strategy=GenerationType.SEQUENCE,generator="OV_RPT_SEQ")
  @Column(name="RPT_KEY")
  private Long reportKey;
  
  @Column(name="RPT_NAME")
  private String reportName;
  
  @Column(name="RPT_DESC")
  private String reportDescription;
  
  @Column(name="KPI_MASTER_KEY")
  private Long kpiMasterKey;
  
  @Column(name="DSBRD_LINK")
  private String dashboardLink;
  
  @Column(name="PUBLSH_IND")
  private String publishIndicator;
  
  @Column(name="PUBLSH_FLDR")
  private String publishFolder;
  
  @Column(name="CHART_TYPE")
  private Long chartType;
  
  @Column(name="AUDIT_CRT_DATE")
  private Timestamp auditCreateDate;
  
  @Column(name="CRT_USER")
  private String createdUser;
  
  @Column(name="UPD_USER")
  private String updatedUser;
  
  @Column(name="TNT_KEY")
  private Long tenantKey;
  
  @Column(name="PLANT_KEY")
  private Long plantKey;
  // getteres and setters methods for the fields.
  }
  </code></pre>
  
  <p>ReportPieChart.java</p>
  
  <pre><code> @Entity
   @Table(name="OV_RPT_PIE_CHART")
   @PrimaryKeyJoinColumn(name="RPT_KEY")
   @DiscriminatorValue(value=AppConstants.REPORT_TYPE_PIE)
  
   public class ReportPieChart extends ReportDetails{
  
  /**
   * 
   */
  private static final long serialVersionUID = 1L;
  
  @Column(name="X_AXIS_VAL")
  private String xAxisValue;
  
  @Column(name="Y_AXIS_VAL")
  private String yAxisValue;
  
  @Column(name="AUDIT_CRT_DATE")
  private Timestamp auditCreateDate;
  
  @Column(name="AUDIT_UPD_DATE")
  private Timestamp auditUpdateDate;
  
  @Column(name="CRT_USER")
  private String createdUser;
  
  @Column(name="UPD_USER")
  private String updateUser;
  
  @Column(name="TNT_KEY")
  private Long tntKey;
  
  @Column(name="PLANT_KEY")
  private Long plantKey;
  // getteres and setters methods for the fields.
  }
  </code></pre>
  
  <p>Please help to resolve this issue.</p>