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https://issues.apache.org/jira/browse/HBASE-16438?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15610669#comment-15610669
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Anoop Sam John commented on HBASE-16438:
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Describing diff possibilities at that time. We keep ref and offset means we
can not keep whole of the index meta in off heap chunk. chunkid+ offset we can
easily keep as both are ints and we can keep ints in offheap BB. But the ref
means we need to have a ref array which is on heap. And we will need another
data structure (chunk only) to keep offset + length. Yes we can avoid length
when there are no tags. But when tags are there, we need to keep length :-(.
This is because tags parts comes after KL, VL, Key and Value. Also missed one
more thing at that time of discuss. ie. we need to keep the seqId 8 bytes)..
When cells in CSLM, it is a long state on the object. Other way would be that
when we copy Cell to MSLAB (or to a temp byte[]) at the time of addition to
Memstore, we need to keep the seqId not as a state in obj. But that should be
put as the last 8 bytes of the cell data bytes. (After key, value and tags).
When MSLAB is off heap this will help us to keep more data off heap. We need
a diff version of cell which can read seqId correctly from last 8 bytes. We
will need decode it. Will need lots of PoC work around diff ideas. All these
goes to other jira which says abt ChunkMap variant.
> 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
>
> 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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