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https://issues.apache.org/jira/browse/HBASE-6311?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13406281#comment-13406281
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chunhui shen commented on HBASE-6311:
-------------------------------------
@ram
In order to keep MVCC for the firstscanner, we retained already deleted KV
output to compacted file in current logic.
What my patch do is retaining delete type KV output to compacted file also if
the above happen:
{code}
if(kv.getMemstoreTS() > maxReadPointToTrackVersions)
return MatchCode.INCLUDE;{code}
Include the delete type KV as the above code
> Data error after majorCompaction caused by keeping MVCC for opened scanners
> ---------------------------------------------------------------------------
>
> Key: HBASE-6311
> URL: https://issues.apache.org/jira/browse/HBASE-6311
> Project: HBase
> Issue Type: Bug
> Components: regionserver
> Affects Versions: 0.94.0
> Reporter: chunhui shen
> Assignee: chunhui shen
> Priority: Blocker
> Attachments: HBASE-6311-test.patch, HBASE-6311v1.patch
>
>
> It is a big problem we found in 0.94, and you could reproduce the problem in
> Trunk using the test case I uploaded.
> When we do compaction, we will use region.getSmallestReadPoint() to keep MVCC
> for opened scanners;
> However,It will make data mistake after majorCompaction because we will skip
> delete type KV but keep the put type kv in the compacted storefile.
> The following is the reason from code:
> In StoreFileScanner, enforceMVCC is false when compaction, so we could read
> the delete type KV,
> However, we will skip this delete type KV in ScanQueryMatcher because
> following code
> {code}
> if (kv.isDelete())
> {
> ...
> if (includeDeleteMarker
> && kv.getMemstoreTS() <= maxReadPointToTrackVersions) {
> System.out.println("add deletes,maxReadPointToTrackVersions="
> + maxReadPointToTrackVersions);
> this.deletes.add(bytes, offset, qualLength, timestamp, type);
> }
> ...
> }
> {code}
> Here maxReadPointToTrackVersions = region.getSmallestReadPoint();
> and kv.getMemstoreTS() > maxReadPointToTrackVersions
> So we won't add this to DeleteTracker.
> Why test case passed if remove the line
> MultiVersionConsistencyControl.setThreadReadPoint(smallestReadPoint);
> Because in the StoreFileScanner#skipKVsNewerThanReadpoint
> {code}
> if (cur.getMemstoreTS() <= readPoint) {
> cur.setMemstoreTS(0);
> }
> {code}
> So if we remove the line
> MultiVersionConsistencyControl.setThreadReadPoint(smallestReadPoint);
> Here readPoint is LONG.MAX_VALUE, we will set memStore ts as 0, so we will
> add it to DeleteTracker in ScanQueryMatcher
> Solution:
> We use smallestReadPoint of region when compaction to keep MVCC for OPENED
> scanner, So we should retain delete type kv in output in the case(Already
> deleted KV is retained in output to make old opened scanner could read this
> KV) even if it is a majorcompaction.
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