[hibernate-issues] [Hibernate-JIRA] Created: (HHH-3360) Custom Oracle Batcher to allow batch updates for versioned data

[Manuel Dominguez Sarmiento (JIRA)]

Custom Oracle Batcher to allow batch updates for versioned data
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                 Key: HHH-3360
                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-3360
             Project: Hibernate3
          Issue Type: Improvement
          Components: core
    Affects Versions: 3.3.0.CR1, 3.2.6, 3.2.5, 3.2.4.sp1, 3.2.4, 3.2.3, 3.2.2, 3.2.1, 3.2.0.ga
         Environment: Oracle 10g R1, 10g R2, 11g R1 (have not tried previous Oracle versions), 11g R1 drivers (older drivers should also work)
            Reporter: Manuel Dominguez Sarmiento
            Priority: Minor
         Attachments: C3P0OracleBatchingBatcher.java, C3P0OracleBatchingBatcherFactory.java, OracleBatchingBatcher.java, OracleBatchingBatcherFactory.java

We have developed a custom Oracle Batcher which allows batching versioned data. The Oracle JDBC driver does not return update counts when using the standard JDBC 2.0 batching mechanism, however the proprietary Oracle batching mechanism allows obtaining the total batch row update count. The update counts are absolutely necessary to detect stale updates.

Although it is not exactly the same, the total row update count is actually enough information to be able to batch versioned data and still detect stale updates.

We'd like to contribute the attached files. They have a compile time dependency on Oracle JDBC. If this is not acceptable, it could be easily solved by using reflection.

Another Batcher is provided for when the Oracle connection is being managed through c3p0 (a common deployment scenario). This has a compile time dependency on c3p0.

A few "dirty" tricks were necessary to pull this off without patching other classes. Specifically, it was necessary to override Java private semantics to obtain BasicExpectation.expectedRowCount. This could be easily solved by adding an accessor method to the Expectation interface.

There is one issue which we are not completely sure of, however so far we have not found any problems. When the Expectation is NONE, there is no way to check whether the total row count is correct or not, even if other batched updates do have expectations with expected row counts. Our understanding is that actually, since batching requires all statements to be of the same type (since the same PreparedStatement / CallableStatement is being used), then either ALL expectations will be NONE, or all will have an expected row count. We'd welcome comments from the Hibernate team. This could also be probably handled better by improving the Expectation interface.

Oracle JDBC docs that explain the Oracle batching model: http://download.oracle.com/docs/cd/B28359_01/java.111/b31224/oraperf.htm#i1059054

As expected, implementing this solution has resulted in drastical improvement in batch processing.

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