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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