Details

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Changes to how Clob values are processed using PostgreSQL81Dialect and its subclasses

A breaking change was made in how Clob values are processed using PostgreSQL81Dialect and its subclasses. The following is copied from the migration guide.

Up to and including 5.2.8, Clob values and values for String, character[], and Character[] attributes that are annotated with @Lob were:

  • bound using Clob representations of the data (using PreparedStatement#setClob or CallableStatement#setClob);

  • retrieved as Clob values (using ResultSet#getClob or CallableStatement#getClob), which were converted to the appropriate Java type;

  • stored as PostgreSQL Large Objects; i.e., an OID for the value is stored in a text column, which refers to the actual data stored in a different (PostgreSQL-specific) table.

In 5.2.9 and 5.2.10, due to the fix for HHH-11477, Clob values and values for String, character[], and Character[] attributes that are annotated with @Lob were:

  • bound using String representations of the data (using PreparedStatement#setString or CallableStatement#setString);

  • retrieved as String values (using ResultSet#getString or CallableStatement#getString), which were converted to the appropriate Java type;

  • stored as variable-length character strings.

In 5.2.11, the fix for HHH-11477 was reverted (HHH-11614) to restore the 5.2.8 behavior.

As a consequence of these changes, data persisted using a version of Hibernate prior to 5.2.9 cannot be read using 5.2.9 or 5.2.10. Data persisted using Hibernate 5.2.9 or 5.2.10 can no longer be read using 5.2.11 or later.

A workaround that can be used in 5.2.9 and 5.2.10 that will restore the 5.2.8/5.2.11 behavior is to override the PostgreSQL dialect with:

public SqlTypeDescriptor getSqlTypeDescriptorOverride(int sqlCode) {
        if( sqlCode == Types.CLOB ){
                return ClobTypeDescriptor.CLOB_BINDING;
        }
        return super.getSqlTypeDescriptorOverride( sqlCode );
}

In addition, any Clob values and values for String, character[], Character[] attributes that are annotated with @Lob that were stored as variable-length character strings using 5.2.9 or 5.2.10 should be updated to store the values as PostgreSQL Large Objects before migrating to 5.2.11.

For example, if variable-length character strings were stored by 5.2.9 or 5.2.10 for the following mapping:

@Entity(name = "TestEntity")
@Table(name = "TEST_ENTITY")
public static class TestEntity {
        @Id
        @GeneratedValue
        private long id;

        @Lob
        String firstLobField;

        @Lob
        String secondLobField;

        @Lob
        Clob clobField;

        ...
}

the variable-length character strings can be converted to PostgreSQL Large Objects by executing the following SQL:

update test_entity
set clobfield = lo_from_bytea( 0, cast( clobfield as bytea ) ),
    firstlobfield = lo_from_bytea( 0, cast( firstlobfield as bytea ) ),
    secondlobfield = lo_from_bytea( 0, cast( secondlobfield as bytea ) )

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