Create SingleKeySqlDrivingQueryInputSource [BATCH-39] about spring-batch HOT 5 CLOSED

Lucas Ward commented

A new class, SingleKeySqlDrivingQueryInputSource has been added to version control. It is a very simple implementation, that is currently read-forward. Restartability still remains to be implemented. I thrashed back and forth about making the input source, 'heavier', but considering other discussions going on about transaction, etc, I am starting to agree witht the concept of using a 'Transactional Buffer' that could be generic to all input sources. I almost created a 'TransactionalInputSourceWrapper' that would implement this functionality, but decided to leave it out.

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Robert Kasanicky commented

The new implementation again uses JdbcTemplate to run the sql queries, what means resource allocation and releasing is done in each iteration. It is necessary to move the resource handling out of the loop to achieve reasonable performance.

I think it makes sense to do the same also for repository implementations.

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Lucas Ward commented

I disagree that the use of JdbcTemplate by default makes it unperformant just because of resource releasing. Regardless of whether or not your use it, the resultset must be released for each 'details query'. You could keep from closing the connection if not using it, but since that's supressed anyway on most data sources that's not an issue either. The biggest difference between this version and the older driving query, performance-wise, is that the older version used a sql query, with the values built into the sql string. (i.e. select from table where id = 5, instead of where id = ?) Since the new version uses prepared statements, the database can now cache the statements, which should result in much greater performance. Although, I will be interested to see the results of performance testing.

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Lucas Ward commented

Added Restartable to InputSource and marked as fixed. There will likely still be some refactoring, but I will reopen or create a new issue to track in that case.

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Dave Syer commented

Assume closed as resolved and released

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