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From "Anoop Sam John (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-15392) Single Cell Get reads two HFileBlocks
Date Fri, 11 Mar 2016 06:54:40 GMT

    [ https://issues.apache.org/jira/browse/HBASE-15392?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15190549#comment-15190549
] 

Anoop Sam John commented on HBASE-15392:
----------------------------------------

{quote}
bq.We check rows in both and they are same. So the return value of compareKeyForNextRow will
be 0.
No we don't!
The seek keys will never be equal to anything, because they are not real keys
{quote}
Again a confusion.. Sorry..
Here to compareKeyForNextRow  we pass 2 Cells. One is the nextIndexedKey (start key of the
next block - we get it from index data).  The other is the current cell.  This is an actual
cell which we read and of this current row..  We have to go to next row as said by SQM.

> Single Cell Get reads two HFileBlocks
> -------------------------------------
>
>                 Key: HBASE-15392
>                 URL: https://issues.apache.org/jira/browse/HBASE-15392
>             Project: HBase
>          Issue Type: Sub-task
>          Components: BucketCache
>            Reporter: stack
>            Assignee: stack
>         Attachments: 15392-0.98-looksee.txt, 15392.wip.patch, 15392v2.wip.patch, 15392v3.wip.patch,
15392v4.patch, HBASE-15392_suggest.patch, gc.png, gc.png, io.png, no_optimize.patch, no_optimize.patch,
reads.png, reads.png, two_seeks.txt
>
>
> As found by Daniel "SystemTap" Pol, a simple Get results in our reading two HFileBlocks,
the one that contains the wanted Cell, and the block that follows.
> Here is a bit of custom logging that logs a stack trace on each HFileBlock read so you
can see the call stack responsible:
> {code}
> 2016-03-03 22:20:30,191 INFO  [B.defaultRpcServer.handler=20,queue=2,port=16020] regionserver.StoreScanner:
START LOOP
> 2016-03-03 22:20:30,192 INFO  [B.defaultRpcServer.handler=20,queue=2,port=16020] regionserver.StoreScanner:
QCODE SEEK_NEXT_COL
> 2016-03-03 22:20:30,192 INFO  [B.defaultRpcServer.handler=20,queue=2,port=16020] hfile.HFileBlockIndex:
STARTED WHILE
> 2016-03-03 22:20:30,192 INFO  [B.defaultRpcServer.handler=20,queue=2,port=16020] hfile.CombinedBlockCache:
OUT OF L2
> 2016-03-03 22:20:30,192 TRACE [B.defaultRpcServer.handler=20,queue=2,port=16020] bucket.BucketCache:
Read offset=31409152, len=2103
> 2016-03-03 22:20:30,192 TRACE [B.defaultRpcServer.handler=20,queue=2,port=16020] bucket.FileIOEngine:
offset=31409152, length=2103
> 2016-03-03 22:20:30,193 TRACE [B.defaultRpcServer.handler=20,queue=2,port=16020] hfile.HFileReaderImpl:
From Cache [blockType=DATA, fileOffset=2055421, headerSize=33, onDiskSizeWithoutHeader=2024,
uncompressedSizeWithoutHeader=2020, prevBlockOffset=2053364, isUseHBaseChecksum=true, checksumType=CRC32C,
bytesPerChecksum=16384, onDiskDataSizeWithHeader=2053, getOnDiskSizeWithHeader=2057, totalChecksumBytes=4,
isUnpacked=true, buf=[org.apache.hadoop.hbase.nio.SingleByteBuff@e19fbd54], dataBeginsWith=\x00\x00\x00)\x00\x00\x01`\x00\x16user995139035672819231,
fileContext=[usesHBaseChecksum=true, checksumType=CRC32C, bytesPerChecksum=16384, blocksize=65536,
encoding=NONE, includesMvcc=true, includesTags=false, compressAlgo=NONE, compressTags=false,
cryptoContext=[cipher=NONE keyHash=NONE]]]
> 2016-03-03 22:20:30,193 TRACE [B.defaultRpcServer.handler=20,queue=2,port=16020] hfile.HFileReaderImpl:
Cache hit return [blockType=DATA, fileOffset=2055421, headerSize=33, onDiskSizeWithoutHeader=2024,
uncompressedSizeWithoutHeader=2020, prevBlockOffset=2053364, isUseHBaseChecksum=true, checksumType=CRC32C,
bytesPerChecksum=16384, onDiskDataSizeWithHeader=2053, getOnDiskSizeWithHeader=2057, totalChecksumBytes=4,
isUnpacked=true, buf=[org.apache.hadoop.hbase.nio.SingleByteBuff@e19fbd54], dataBeginsWith=\x00\x00\x00)\x00\x00\x01`\x00\x16user995139035672819231,
fileContext=[usesHBaseChecksum=true, checksumType=CRC32C, bytesPerChecksum=16384, blocksize=65536,
encoding=NONE, includesMvcc=true, includesTags=false, compressAlgo=NONE, compressTags=false,
cryptoContext=[cipher=NONE keyHash=NONE]]]
> java.lang.Throwable
>         at org.apache.hadoop.hbase.io.hfile.HFileReaderImpl.readBlock(HFileReaderImpl.java:1515)
>         at org.apache.hadoop.hbase.io.hfile.HFileBlockIndex$CellBasedKeyBlockIndexReader.loadDataBlockWithScanInfo(HFileBlockIndex.java:324)
>         at org.apache.hadoop.hbase.io.hfile.HFileReaderImpl$HFileScannerImpl.seekTo(HFileReaderImpl.java:831)
>         at org.apache.hadoop.hbase.io.hfile.HFileReaderImpl$HFileScannerImpl.reseekTo(HFileReaderImpl.java:812)
>         at org.apache.hadoop.hbase.regionserver.StoreFileScanner.reseekAtOrAfter(StoreFileScanner.java:288)
>         at org.apache.hadoop.hbase.regionserver.StoreFileScanner.reseek(StoreFileScanner.java:198)
>         at org.apache.hadoop.hbase.regionserver.NonLazyKeyValueScanner.doRealSeek(NonLazyKeyValueScanner.java:54)
>         at org.apache.hadoop.hbase.regionserver.KeyValueHeap.generalizedSeek(KeyValueHeap.java:321)
>         at org.apache.hadoop.hbase.regionserver.KeyValueHeap.requestSeek(KeyValueHeap.java:279)
>         at org.apache.hadoop.hbase.regionserver.StoreScanner.reseek(StoreScanner.java:806)
>         at org.apache.hadoop.hbase.regionserver.StoreScanner.seekAsDirection(StoreScanner.java:795)
>         at org.apache.hadoop.hbase.regionserver.StoreScanner.next(StoreScanner.java:624)
>         at org.apache.hadoop.hbase.regionserver.KeyValueHeap.next(KeyValueHeap.java:153)
>         at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.populateResult(HRegion.java:5703)
>         at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.nextInternal(HRegion.java:5849)
>         at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.nextRaw(HRegion.java:5622)
>         at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.next(HRegion.java:5598)
>         at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.next(HRegion.java:5584)
>         at org.apache.hadoop.hbase.regionserver.RSRpcServices.get(RSRpcServices.java:2187)
>         at org.apache.hadoop.hbase.regionserver.RSRpcServices.get(RSRpcServices.java:2123)
>         at org.apache.hadoop.hbase.protobuf.generated.ClientProtos$ClientService$2.callBlockingMethod(ClientProtos.java:33512)
>         at org.apache.hadoop.hbase.ipc.RpcServer.call(RpcServer.java:2229)
>         at org.apache.hadoop.hbase.ipc.CallRunner.run(CallRunner.java:109)
>         at org.apache.hadoop.hbase.ipc.RpcExecutor.consumerLoop(RpcExecutor.java:136)
>         at org.apache.hadoop.hbase.ipc.RpcExecutor$1.run(RpcExecutor.java:111)
>         at java.lang.Thread.run(Thread.java:745)
> 2016-03-03 22:20:30,193 INFO  [B.defaultRpcServer.handler=20,queue=2,port=16020] hfile.HFileBlockIndex:
READ [blockType=DATA, fileOffset=2055421, headerSize=33, onDiskSizeWithoutHeader=2024, uncompressedSizeWithoutHeader=2020,
prevBlockOffset=2053364, isUseHBaseChecksum=true, checksumType=CRC32C, bytesPerChecksum=16384,
onDiskDataSizeWithHeader=2053, getOnDiskSizeWithHeader=2057, totalChecksumBytes=4, isUnpacked=true,
buf=[org.apache.hadoop.hbase.nio.SingleByteBuff@e19fbd54], dataBeginsWith=\x00\x00\x00)\x00\x00\x01`\x00\x16user995139035672819231,
fileContext=[usesHBaseChecksum=true, checksumType=CRC32C, bytesPerChecksum=16384, blocksize=65536,
encoding=NONE, includesMvcc=true, includesTags=false, compressAlgo=NONE, compressTags=false,
cryptoContext=[cipher=NONE keyHash=NONE]]]
> 2016-03-03 22:20:30,193 INFO  [B.defaultRpcServer.handler=20,queue=2,port=16020] hfile.HFileBlockIndex:
DATA BLOCK IS TRUE BREAK
> 2016-03-03 22:20:30,193 INFO  [B.defaultRpcServer.handler=20,queue=2,port=16020] hfile.HFileBlockIndex:
RETURNING
> 2016-03-03 22:20:30,194 INFO  [B.defaultRpcServer.handler=20,queue=2,port=16020] regionserver.StoreScanner:
QCODE INCLUDE
> 2016-03-03 22:20:30,194 INFO  [B.defaultRpcServer.handler=20,queue=2,port=16020] regionserver.StoreScanner:
QCODE SKIP
> 2016-03-03 22:20:30,194 INFO  [B.defaultRpcServer.handler=20,queue=2,port=16020] hfile.CombinedBlockCache:
OUT OF L2
> 2016-03-03 22:20:30,194 TRACE [B.defaultRpcServer.handler=20,queue=2,port=16020] bucket.BucketCache:
Read offset=30932992, len=2103
> 2016-03-03 22:20:30,194 TRACE [B.defaultRpcServer.handler=20,queue=2,port=16020] bucket.FileIOEngine:
offset=30932992, length=2103
> 2016-03-03 22:20:30,194 TRACE [B.defaultRpcServer.handler=20,queue=2,port=16020] hfile.HFileReaderImpl:
From Cache [blockType=DATA, fileOffset=2057478, headerSize=33, onDiskSizeWithoutHeader=2024,
uncompressedSizeWithoutHeader=2020, prevBlockOffset=2055421, isUseHBaseChecksum=true, checksumType=CRC32C,
bytesPerChecksum=16384, onDiskDataSizeWithHeader=2053, getOnDiskSizeWithHeader=2057, totalChecksumBytes=4,
isUnpacked=true, buf=[org.apache.hadoop.hbase.nio.SingleByteBuff@6063ac95], dataBeginsWith=\x00\x00\x00)\x00\x00\x01`\x00\x16user995698996184959679,
fileContext=[usesHBaseChecksum=true, checksumType=CRC32C, bytesPerChecksum=16384, blocksize=65536,
encoding=NONE, includesMvcc=true, includesTags=false, compressAlgo=NONE, compressTags=false,
cryptoContext=[cipher=NONE keyHash=NONE]]]
> 2016-03-03 22:20:30,194 TRACE [B.defaultRpcServer.handler=20,queue=2,port=16020] hfile.HFileReaderImpl:
Cache hit return [blockType=DATA, fileOffset=2057478, headerSize=33, onDiskSizeWithoutHeader=2024,
uncompressedSizeWithoutHeader=2020, prevBlockOffset=2055421, isUseHBaseChecksum=true, checksumType=CRC32C,
bytesPerChecksum=16384, onDiskDataSizeWithHeader=2053, getOnDiskSizeWithHeader=2057, totalChecksumBytes=4,
isUnpacked=true, buf=[org.apache.hadoop.hbase.nio.SingleByteBuff@6063ac95], dataBeginsWith=\x00\x00\x00)\x00\x00\x01`\x00\x16user995698996184959679,
fileContext=[usesHBaseChecksum=true, checksumType=CRC32C, bytesPerChecksum=16384, blocksize=65536,
encoding=NONE, includesMvcc=true, includesTags=false, compressAlgo=NONE, compressTags=false,
cryptoContext=[cipher=NONE keyHash=NONE]]]
> java.lang.Throwable
>         at org.apache.hadoop.hbase.io.hfile.HFileReaderImpl.readBlock(HFileReaderImpl.java:1515)
>         at org.apache.hadoop.hbase.io.hfile.HFileReaderImpl$HFileScannerImpl.readNextDataBlock(HFileReaderImpl.java:906)
>         at org.apache.hadoop.hbase.io.hfile.HFileReaderImpl$HFileScannerImpl.isNextBlock(HFileReaderImpl.java:1106)
>         at org.apache.hadoop.hbase.io.hfile.HFileReaderImpl$HFileScannerImpl.positionForNextBlock(HFileReaderImpl.java:1100)
>         at org.apache.hadoop.hbase.io.hfile.HFileReaderImpl$HFileScannerImpl._next(HFileReaderImpl.java:1118)
>         at org.apache.hadoop.hbase.io.hfile.HFileReaderImpl$HFileScannerImpl.next(HFileReaderImpl.java:1139)
>         at org.apache.hadoop.hbase.regionserver.StoreFileScanner.next(StoreFileScanner.java:152)
>         at org.apache.hadoop.hbase.regionserver.KeyValueHeap.next(KeyValueHeap.java:114)
>         at org.apache.hadoop.hbase.regionserver.StoreScanner.next(StoreScanner.java:628)
>         at org.apache.hadoop.hbase.regionserver.KeyValueHeap.next(KeyValueHeap.java:153)
>         at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.populateResult(HRegion.java:5703)
>         at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.nextInternal(HRegion.java:5849)
>         at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.nextRaw(HRegion.java:5622)
>         at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.next(HRegion.java:5598)
>         at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.next(HRegion.java:5584)
>         at org.apache.hadoop.hbase.regionserver.RSRpcServices.get(RSRpcServices.java:2187)
>         at org.apache.hadoop.hbase.regionserver.RSRpcServices.get(RSRpcServices.java:2123)
>         at org.apache.hadoop.hbase.protobuf.generated.ClientProtos$ClientService$2.callBlockingMethod(ClientProtos.java:33512)
>         at org.apache.hadoop.hbase.ipc.RpcServer.call(RpcServer.java:2229)
>         at org.apache.hadoop.hbase.ipc.CallRunner.run(CallRunner.java:109)
>         at org.apache.hadoop.hbase.ipc.RpcExecutor.consumerLoop(RpcExecutor.java:136)
>         at org.apache.hadoop.hbase.ipc.RpcExecutor$1.run(RpcExecutor.java:111)
>         at java.lang.Thread.run(Thread.java:745)
> 2016-03-03 22:20:30,195 INFO  [B.defaultRpcServer.handler=20,queue=2,port=16020] regionserver.StoreScanner:
QCODE DONE
> {code}
> We are in StoreScanner#next.
> Matcher does SEEK_NEXT_COL.
> We pull in the block that has our Cell in it.
> Matcher does INCLUDE
> Then Matcher does SKIP
> SKIP has us go read the next block.
> Then Matcher does DONE.
> Why ain't I getting to DONE after INCLUDE?
> Any clues?
> This code has been like this a while.



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