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https://issues.apache.org/jira/browse/HBASE-11425?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14355497#comment-14355497
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stack commented on HBASE-11425:
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bq. I wanted to come to this topic. This is hard coded now. Can this be made
configurable? If this can be larger value,like block size, better as per our
changes
Yeah, configurable sounds right but thinking on it more, rare will be the case
that the fuzzy hfile block will fit into the BC hard-coded block.
bq. May be that should be tried after a delay?
Would this be a new block type? One that is not backed by BC? No on delay.
Flag its happening and move on. It'd be an offheap allocation I suppose so will
be delay enough (smlie).
bq. Am I making it clear?
Yes.
bq. Some thing like a ServerCell which extend Cell?
We can't give users an API that has you get data from a BB but you need to use
the enclosing Cell to figure where to read from and how much. Users will kick
us out!
bq. Yes the extra BB wrapper which has to be created every time one calls
getXXXArray().
Would be interesting to see cost. Would be sweet if only one readpath... but
I'd imagine the perf difference will be too great so we'll have to have two.
bq. It reads data from BB bypassing the BB APIs.
Add this to doc.
Thanks.
> Cell/DBB end-to-end on the read-path
> ------------------------------------
>
> Key: HBASE-11425
> URL: https://issues.apache.org/jira/browse/HBASE-11425
> Project: HBase
> Issue Type: Umbrella
> Components: regionserver, Scanners
> Affects Versions: 0.99.0
> Reporter: Anoop Sam John
> Assignee: Anoop Sam John
> Attachments: Offheap reads in HBase using BBs_final.pdf
>
>
> Umbrella jira to make sure we can have blocks cached in offheap backed cache.
> In the entire read path, we can refer to this offheap buffer and avoid onheap
> copying.
> The high level items I can identify as of now are
> 1. Avoid the array() call on BB in read path.. (This is there in many
> classes. We can handle class by class)
> 2. Support Buffer based getter APIs in cell. In read path we will create a
> new Cell with backed by BB. Will need in CellComparator, Filter (like SCVF),
> CPs etc.
> 3. Avoid KeyValue.ensureKeyValue() calls in read path - This make byte copy.
> 4. Remove all CP hooks (which are already deprecated) which deal with KVs.
> (In read path)
> Will add subtasks under this.
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