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https://issues.apache.org/jira/browse/TRAFODION-2946?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16497687#comment-16497687
]
ASF GitHub Bot commented on TRAFODION-2946:
-------------------------------------------
Github user sandhyasun commented on a diff in the pull request:
https://github.com/apache/trafodion/pull/1586#discussion_r192318454
--- Diff: core/sql/runtimestats/sscpipc.cpp ---
@@ -907,3 +910,53 @@ void
SscpNewIncomingConnectionStream::processSecInvReq()
request->decrRefCount();
}
+void SscpNewIncomingConnectionStream::processLobLockReq()
+{
+ IpcMessageObjVersion msgVer = getNextObjVersion();
+
+ ex_assert(msgVer <= currRtsStatsReqVersionNumber, "Up-rev message
received.");
+ NAHeap *statsHeap = NULL;
+ LobLockRequest *request = new(getHeap())
+ LobLockRequest(getHeap());
+
+ *this >> *request;
+ ex_assert( !moreObjects(), "unknown object follows LobLockRequest.");
+ SscpGlobals *sscpGlobals = getSscpGlobals();
+ StatsGlobals *statsGlobals = sscpGlobals->getStatsGlobals();
+ int error = statsGlobals->getStatsSemaphore(sscpGlobals->getSemId(),
+ sscpGlobals->myPin());
+ statsHeap = statsGlobals->getStatsHeap();
+ char *ll = new (statsHeap) char [LOB_LOCK_ID_SIZE];
+ memcpy(ll,request->getLobLockId(),LOB_LOCK_ID_SIZE+1);
+ SyncHashQueue *lobLockList = statsGlobals->getLobLocks();
+ if (ll[0] == '+') // If it's a positive value, we are supposed to insert
it.
--- End diff --
To address the scenario where 2 clients on different nodes check for a lock
and being the process of setting it, instead of simply setting/inserting into
the HashQueue, we should do an extra check for existence here before setting .
If it's already there, some other process on another node may have propagated
the same lockLockId first . So we should send a diagsArea back here to indicate
the set for this client/process failed.
> LOB : Locking/transaction support needed for LOB files for DDL and IUD
> operations
> ----------------------------------------------------------------------------------
>
> Key: TRAFODION-2946
> URL: https://issues.apache.org/jira/browse/TRAFODION-2946
> Project: Apache Trafodion
> Issue Type: New Feature
> Components: dtm, sql-general
> Affects Versions: any
> Reporter: Sandhya Sundaresan
> Assignee: Sandhya Sundaresan
> Priority: Major
> Attachments: Locking issue for concurrent access of LOBs.docx
>
>
> Trafodion DTM needs to recognize LOB HDFS data files that contain the actual
> critical data for a LOB column and treat them as part of the Trafodion object
> that contains the LOB column. The Trafodion table itself contains the LOB
> handle that can be used to derive the LOB data file name/location.
> DDL operations performed on LOB tables today only work on the Trafodion
> table. The dependent HDFS data files are not treated as part of the DDL
> transaction. ANy parallel operations or errors during create/drop will leave
> the table in an inconsistent state.
>
> DML operations on any LOB table only work on the LOB table and it's dependent
> descriptor tables that are also Trafodion tables (contain offset/length
> information in the HDFS data file for each LOB column). But the HDFS data
> file operation is not covered as part of the transaction. So any IUD error
> will leave the LOB table in an inconsistent state .
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