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https://issues.apache.org/jira/browse/HBASE-5331?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13200019#comment-13200019
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Sandy Pratt commented on HBASE-5331:
------------------------------------
Woops, looks like this is already fixed on trunk! Feel free to close this...
> Off by one bug in util.HMerge
> -----------------------------
>
> Key: HBASE-5331
> URL: https://issues.apache.org/jira/browse/HBASE-5331
> Project: HBase
> Issue Type: Bug
> Components: util
> Affects Versions: 0.90.1
> Environment: NA
> Reporter: Sandy Pratt
> Fix For: 0.94.0
>
>
> It looks like there's an off by one bug in the OfflineMerger constructor in
> util.HMerge:
> InternalScanner rootScanner =
> root.getScanner(scan);
> try {
> List<KeyValue> results = new ArrayList<KeyValue>();
> while(rootScanner.next(results)) {
> for(KeyValue kv: results) {
> HRegionInfo info = Writables.getHRegionInfoOrNull(kv.getValue());
> if (info != null) {
> metaRegions.add(info);
> }
> }
> }
> } finally {
> ...
> }
> That call to InternalScanner.next() in the while condition returns true if
> there's another result *after* the one it just loaded into the out param.
> That is, after it reads the last row into the 'results' collection, it
> returns false and the loop exits with that last row unread. It probably
> wants to be structured more like this:
> final InternalScanner metaScanner = meta.getScanner(scan); List<KeyValue>
> results = Lists.newArrayList();
> while (true) {
> boolean hasMore = metaScanner.next(results);
> for (KeyValue kv : results) {
> HRegionInfo hri = Writables.getHRegionInfoOrNull(kv.getValue());
> if (hri != null) {
> regionInfo.add(hri);
> }
> }
>
> if (!hasMore) {
> break;
> }
> }
> The loop in util.HMerge is scanning ROOT for META regions. So this bug will
> only be hit when there is more than one region of META. Personally, I don't
> have any installations with more than one META region, and I'm not sure if
> anyone does, so this might be a moot point.
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