[
https://issues.apache.org/jira/browse/HBASE-5569?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13232349#comment-13232349
]
Lars Hofhansl commented on HBASE-5569:
--------------------------------------
Here's my theory...
In ScanQueryMatcher we have this:
{code}
byte type = kv.getType();
if (kv.isDelete()) {
if (!keepDeletedCells) {
...
this.deletes.add(bytes, offset, qualLength, timestamp, type);
}
...
} else if (!this.deletes.isEmpty()) {
DeleteResult deleteResult = deletes.isDeleted(bytes, offset, qualLength,
timestamp);
...
}
{code}
And in StoreScanner.resetScannerStack
{code}
// Reset the state of the Query Matcher and set to top row.
// Only reset and call setRow if the row changes; avoids confusing the
// query matcher if scanning intra-row.
...
if ((matcher.row == null) || !kv.matchingRow(matcher.row)) {
matcher.reset();
matcher.setRow(kv.getRow());
}
{code}
So, the SQM might already have a delete registered, or might miss a delete.
With KEEP_DELETED_CELLS that race does not happen, because deletes are simply
not registered.
> Do not collect deleted KVs when they are still in use by a scanner.
> -------------------------------------------------------------------
>
> Key: HBASE-5569
> URL: https://issues.apache.org/jira/browse/HBASE-5569
> Project: HBase
> Issue Type: Bug
> Reporter: Lars Hofhansl
> Assignee: Lars Hofhansl
> Fix For: 0.94.0, 0.96.0
>
> Attachments: 5569-v2.txt, 5569.txt,
> TestAtomicOperation-output.trunk_120313.rar
>
>
> I noticed this because TestAtomicOperation.testMultiRowMutationMultiThreads
> fails rarely.
> The solution is similar to HBASE-2856, where expired KVs are not collected
> when in use by a scanner.
> ---
> What I pieced together so far is that it is the *scanning* side that has
> problems sometimes.
> Every time I see a assertion failure in the log I see this before:
> {quote}
> 2012-03-12 21:48:49,523 DEBUG [Thread-211] regionserver.StoreScanner(499):
> Storescanner.peek() is changed where before =
> rowB/colfamily11:qual1/75366/Put/vlen=6,and after =
> rowB/colfamily11:qual1/75203/DeleteColumn/vlen=0
> {quote}
> The order of if the Put and Delete is sometimes reversed.
> The test threads should always see exactly one KV, if the "before" was the
> Put the thread see 0 KVs, if the "before" was the Delete the threads see 2
> KVs.
> This debug message comes from StoreScanner to checkReseek. It seems we still
> some consistency issue with scanning sometimes :(
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators:
https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira
