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https://issues.apache.org/jira/browse/TRAFODION-1435?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15511097#comment-15511097
 ] 

ASF GitHub Bot commented on TRAFODION-1435:
-------------------------------------------

Github user DaveBirdsall commented on a diff in the pull request:

    https://github.com/apache/incubator-trafodion/pull/713#discussion_r79925711
  
    --- Diff: 
core/sqf/src/seatrans/hbase-trx/src/main/java/org/apache/hadoop/hbase/coprocessor/transactional/SsccRegionEndpoint.java.tmpl
 ---
    @@ -2594,7 +2994,76 @@ CoprocessorService, Coprocessor {
         SsccCheckAndPutRegionTxResponse checkAndPutRegionTxResponse = 
checkAndPutRegionTxResponseBuilder.build();
     
         done.run(checkAndPutRegionTxResponse);
    -    */
    +  }
    +
    +  /**
    +   * Processes a checkAndDelete operation using a region transaction
    +   * @param long transactionId
    +   * @param byte[] row
    +   * @param byte[] family
    +   * @param byte[] qualifier
    +   * @param byte[] value
    +   * @param Delete delete
    +   * @param boolean autoCommit
    +   * @return boolean
    +   * @throws IOException
    +   */
    +  public boolean checkAndDeleteRegionTx(long tid, long startId,
    +                                byte[] row, byte[] family,
    +                                byte[] qualifier, byte[] value,
    +                                Delete delete, boolean autoCommit) throws 
IOException {
    +
    +    if (LOG.isTraceEnabled()) LOG.trace("Enter checkAndDeleteRegionTx, 
tid: " + tid);
    +    SsccTransactionState state = this.beginTransIfNotExist(tid, startId, 
true); // This is a regionTX
    +    boolean result = false;
    +    byte[] rsValue = null;
    +
    +    Get get = new Get(row);
    +    get.addColumn(family, qualifier);
    +
    +    Result rs = this.get(tid, startId, get);
    +
    +    boolean valueIsNull = value == null ||
    --- End diff --
    
    I assume this is an HBase-ism. I wonder how zero-length varchar strings are 
represented?


> SQL operations not always performed transactionally with AUTOCOMMIT OFF
> -----------------------------------------------------------------------
>
>                 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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