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https://issues.apache.org/jira/browse/TRAFODION-1435?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sean Broeder updated TRAFODION-1435:
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Summary: SQL operations not always performed transactionally (was: SQL
operations not always performed transactionally with AUTOCOMMIT OFF)
> SQL operations not always performed transactionally
> ---------------------------------------------------
>
> Key: TRAFODION-1435
> URL: https://issues.apache.org/jira/browse/TRAFODION-1435
> Project: Apache Trafodion
> Issue Type: Improvement
> Components: dtm
> Affects Versions: 0.6 (pre-incubation)
> Reporter: Sean Broeder
> Assignee: Sean Broeder
> Original Estimate: 672h
> Remaining Estimate: 672h
>
> For single region, single row operations (both IDU DML as well as select) SQL
> will avoid beginning a transaction and perform the operation directly in
> HBase.
> The feeling was that for single row operations a trasnaction was not
> necessary as HBase would make the operation atomic and provide the necessary
> guarantees. The problem is this circumvents the endpoint coprocessor and
> makes conflict detection with other concurrent transactions impossible.
> For performance reasons we should try to approximate the autocommit behavior
> as much as possible while preserving the conflict detection. We can achieve
> this by implementing 'region transactions' whereby the region will create its
> own transaction identifier when a nontransactional operation arrives in the
> coprocessor. We will need to override all HTable nontransactional operations
> in both the TransactionalTable and SsccTransactionalTable classes. The
> override will create a new transaction identifier specific to the region
> transaction and then use that for all modifications as if it were issued by
> the DTM.
> The transaction identifier needs to be unique so that other threads
> performing similar operations do not get confused at conflict resolution
> time. One possibility is to maintain an AtomicLong in the region that can be
> incremented whenever such a transaction is needed. This keeps all processing
> inside the region and eliminates any RPC to another server process.
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