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https://issues.apache.org/jira/browse/HBASE-16438?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15954534#comment-15954534
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Anoop Sam John commented on HBASE-16438:
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On seqId being in which chunk.. We should be carefully taking a call.. One
disadv of having it in data chunk is that, when the Cell is in active segment
(Not ChunkMapped) and a parallel read happens, we will have to match its seqId
against the read pnt of that Read request. For this, if the seqId is in Cell
object itself as a long state, we have that value ready for compare. If at that
time itself, we moved that as 8 bytes after key and value bytes in data chunk,
we will have to decode the seqId from the 8 bytes. This will happen for every
cell. More over, this MSLAB copy is a top level step which happens even for
DefaultMemstore. So we may end up doing this way of encoding 8 bytes in chunk
for all cases. (There is no in memory compaction or no chunk map based flush)..
All such cases, this impact will come. So pls be careful abt making such a
choice.
> Create a cell type so that chunk id is embedded in it
> -----------------------------------------------------
>
> Key: HBASE-16438
> URL: https://issues.apache.org/jira/browse/HBASE-16438
> Project: HBase
> Issue Type: Sub-task
> Affects Versions: 2.0.0
> Reporter: ramkrishna.s.vasudevan
> Assignee: ramkrishna.s.vasudevan
> Attachments: HBASE-16438_1.patch,
> HBASE-16438_3_ChunkCreatorwrappingChunkPool.patch,
> HBASE-16438_4_ChunkCreatorwrappingChunkPool.patch,
> HBASE-16438_8_ChunkCreatorwrappingChunkPool_withchunkRef.patch,
> HBASE-16438_9_ChunkCreatorwrappingChunkPool_withchunkRef.patch,
> HBASE-16438.patch, MemstoreChunkCell_memstoreChunkCreator_oldversion.patch,
> MemstoreChunkCell_trunk.patch
>
>
> For CellChunkMap we may need a cell such that the chunk out of which it was
> created, the id of the chunk be embedded in it so that when doing flattening
> we can use the chunk id as a meta data. More details will follow once the
> initial tasks are completed.
> Why we need to embed the chunkid in the Cell is described by [~anastas] in
> this remark over in parent issue
> https://issues.apache.org/jira/browse/HBASE-14921?focusedCommentId=15244119&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-15244119
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