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https://issues.apache.org/jira/browse/HBASE-6269?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13401930#comment-13401930
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Anoop Sam John commented on HBASE-6269:
---------------------------------------
@ShiXing
Thanks for ur detailed explanation. Yes I had gone through the code in more
detail when the Lazy seeks happens.
Both the files are getting lazy seeked with same fake KV. And later in
pollReadlKV() the 1st file's scanner is selected as scanner as both the KVs in
the files are same.
> Lazyseek should use the maxSequenseId StoreFile's KeyValue as the latest
> KeyValue
> ---------------------------------------------------------------------------------
>
> Key: HBASE-6269
> URL: https://issues.apache.org/jira/browse/HBASE-6269
> Project: HBase
> Issue Type: Bug
> Components: regionserver
> Affects Versions: 0.94.0
> Reporter: ShiXing
> Assignee: ShiXing
> Attachments: HBASE-6269-trunk-V1.patch, HBASE-6269-v1.patch
>
>
> When I fix the bug HBASE-6195, there is happened to find sometimes the test
> case will fail, https://builds.apache.org/job/HBase-0.94/259/.
> If there are two Put/Increment with same row, family, qualifier, timestamp
> and different memstoreTS, after each Put/Increment, we do a memstore flush.
> So there will be two StoreFile with same KeyValue(except memstoreTS and
> SequenceId).
> When I got the row, I always got the old records, the test case like this:
> {code}
> public void testPutWithMemStoreFlush() throws Exception {
> Configuration conf = HBaseConfiguration.create();
> String method = "testPutWithMemStoreFlush";
> byte[] tableName = Bytes.toBytes(method);
> byte[] family = Bytes.toBytes("family");;
> byte[] qualifier = Bytes.toBytes("qualifier");
> byte[] row = Bytes.toBytes("putRow");
> byte[] value = null;
> this.region = initHRegion(tableName, method, conf, family);
> Put put = null;
> Get get = null;
> List<KeyValue> kvs = null;
> Result res = null;
>
> put = new Put(row);
> value = Bytes.toBytes("value0");
> put.add(family, qualifier, 1234567l, value);
> region.put(put);
> System.out.print("get value before flush after put value0 : ");
> get = new Get(row);
> get.addColumn(family, qualifier);
> get.setMaxVersions();
> res = this.region.get(get, null);
> kvs = res.getColumn(family, qualifier);
> for (int i = 0; i < kvs.size(); i++) {
> System.out.println(Bytes.toString(kvs.get(i).getValue()));
> }
> region.flushcache();
>
> System.out.print("get value after flush after put value0 : ");
> get = new Get(row);
> get.addColumn(family, qualifier);
> get.setMaxVersions();
> res = this.region.get(get, null);
> kvs = res.getColumn(family, qualifier);
> for (int i = 0; i < kvs.size(); i++) {
> System.out.println(Bytes.toString(kvs.get(i).getValue()));
> }
>
> put = new Put(row);
> value = Bytes.toBytes("value1");
> put.add(family, qualifier, 1234567l, value);
> region.put(put);
> System.out.print("get value before flush after put value1 : ");
> get = new Get(row);
> get.addColumn(family, qualifier);
> get.setMaxVersions();
> res = this.region.get(get, null);
> kvs = res.getColumn(family, qualifier);
> for (int i = 0; i < kvs.size(); i++) {
> System.out.println(Bytes.toString(kvs.get(i).getValue()));
> }
> region.flushcache();
> System.out.print("get value after flush after put value1 : ");
> get = new Get(row);
> get.addColumn(family, qualifier);
> get.setMaxVersions();
> res = this.region.get(get, null);
> kvs = res.getColumn(family, qualifier);
> for (int i = 0; i < kvs.size(); i++) {
> System.out.println(Bytes.toString(kvs.get(i).getValue()));
> }
>
> put = new Put(row);
> value = Bytes.toBytes("value2");
> put.add(family, qualifier, 1234567l, value);
> region.put(put);
> System.out.print("get value before flush after put value2 : ");
> get = new Get(row);
> get.addColumn(family, qualifier);
> get.setMaxVersions();
> res = this.region.get(get, null);
> kvs = res.getColumn(family, qualifier);
> for (int i = 0; i < kvs.size(); i++) {
> System.out.println(Bytes.toString(kvs.get(i).getValue()));
> }
> region.flushcache();
> System.out.print("get value after flush after put value2 : ");
> get = new Get(row);
> get.addColumn(family, qualifier);
> get.setMaxVersions();
> res = this.region.get(get, null);
> kvs = res.getColumn(family, qualifier);
> for (int i = 0; i < kvs.size(); i++) {
> System.out.println(Bytes.toString(kvs.get(i).getValue()));
> }
> }
> {code}
> and the result print as followed:
> {code}
> get value before flush after put value0 : value0
> get value after flush after put value0 : value0
> get value before flush after put value1 : value1
> get value after flush after put value1 : value0
> get value before flush after put value2 : value2
> get value after flush after put value2 : value0
> {code}
> I analyze the code for StoreFileScanner with lazy seek, the StoreFileScanners
> are sorted by SequenceId, so the latest StoreFile is on the top KeyValueHeap,
> and the KeyValue for latest StoreFile will comapre to the second latest
> StoreFile, but the second latest StoreFile generated the fake row for same
> row, family, qualifier excepts the timestamp( maximum), memstoreTS(0). And
> the latest KeyValue recognized as not latest than the second latest.
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