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https://issues.apache.org/jira/browse/HBASE-11591?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14106424#comment-14106424
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ramkrishna.s.vasudevan commented on HBASE-11591:
------------------------------------------------
[~jeffreyz]
bq.I think it's fine either keeping existing behavior or add handling for such
cases
Then I think the above change is not necessary and only handle the case as per
the initial patch where we handle same KVs case. The later patches attached is
some how trying to make the mvcc accept the bulk load files and make it visible
just because we are setting the bulk load file's seq id to the KV from the bulk
loaded file.
I think if we have to maintain the behaviour then only handle the case of same
Kvs should be fine. If not the other changes are necessary. This is my take on
this. Pls feel free to correct me.
But thinking of cases like [~jerryhe] then this change is right and for that we
need to handle all cases.
What do other guys think?
> Scanner fails to retrieve KV from bulk loaded file with highest sequence id
> than the cell's mvcc in a non-bulk loaded file
> ---------------------------------------------------------------------------------------------------------------------------
>
> Key: HBASE-11591
> URL: https://issues.apache.org/jira/browse/HBASE-11591
> Project: HBase
> Issue Type: Bug
> Affects Versions: 0.99.0
> Reporter: ramkrishna.s.vasudevan
> Assignee: ramkrishna.s.vasudevan
> Priority: Critical
> Fix For: 0.99.0
>
> Attachments: HBASE-11591.patch, HBASE-11591_1.patch,
> HBASE-11591_2.patch, HBASE-11591_3.patch, HBASE-11591_5.patch,
> TestBulkload.java, hbase-11591-03-02.patch, hbase-11591-03-jeff.patch
>
>
> See discussion in HBASE-11339.
> When we have a case where there are same KVs in two files one produced by
> flush/compaction and the other thro the bulk load.
> Both the files have some same kvs which matches even in timestamp.
> Steps:
> Add some rows with a specific timestamp and flush the same.
> Bulk load a file with the same data.. Enusre that "assign seqnum" property is
> set.
> The bulk load should use HFileOutputFormat2 (or ensure that we write the
> bulk_time_output key).
> This would ensure that the bulk loaded file has the highest seq num.
> Assume the cell in the flushed/compacted store file is
> row1,cf,cq,ts1, value1 and the cell in the bulk loaded file is
> row1,cf,cq,ts1,value2
> (There are no parallel scans).
> Issue a scan on the table in 0.96. The retrieved value is
> row1,cf1,cq,ts1,value2
> But the same in 0.98 will retrieve row1,cf1,cq,ts2,value1.
> This is a behaviour change. This is because of this code
> {code}
> public int compare(KeyValueScanner left, KeyValueScanner right) {
> int comparison = compare(left.peek(), right.peek());
> if (comparison != 0) {
> return comparison;
> } else {
> // Since both the keys are exactly the same, we break the tie in favor
> // of the key which came latest.
> long leftSequenceID = left.getSequenceID();
> long rightSequenceID = right.getSequenceID();
> if (leftSequenceID > rightSequenceID) {
> return -1;
> } else if (leftSequenceID < rightSequenceID) {
> return 1;
> } else {
> return 0;
> }
> }
> }
> {code}
> Here in 0.96 case the mvcc of the cell in both the files will have 0 and so
> the comparison will happen from the else condition . Where the seq id of the
> bulk loaded file is greater and would sort out first ensuring that the scan
> happens from that bulk loaded file.
> In case of 0.98+ as we are retaining the mvcc+seqid we are not making the
> mvcc as 0 (remains a non zero positive value). Hence the compare() sorts out
> the cell in the flushed/compacted file. Which means though we know the
> lateset file is the bulk loaded file we don't scan the data.
> Seems to be a behaviour change. Will check on other corner cases also but we
> are trying to know the behaviour of bulk load because we are evaluating if it
> can be used for MOB design.
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