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https://issues.apache.org/jira/browse/HBASE-4683?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13166601#comment-13166601
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Mikhail Bautin commented on HBASE-4683:
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This is from HFileBlockIndex.java, line 202 (trunk): boolean shouldCache =
cacheBlocks || (lookupLevel < searchTreeLevel)
On the other hand, in HFileReaderV2 we have: cacheBlock &=
cacheConf.shouldCacheDataOnRead().
So currently, when we disable block caching, we don't even cache data blocks,
and there is a valid issue to be fixed in this JIRA.
> Create config option to only cache index blocks
> -----------------------------------------------
>
> Key: HBASE-4683
> URL: https://issues.apache.org/jira/browse/HBASE-4683
> Project: HBase
> Issue Type: New Feature
> Reporter: Lars Hofhansl
> Priority: Minor
> Fix For: 0.94.0
>
> Attachments: 4683-v2.txt, 4683.txt
>
>
> This would add a new boolean config option: hfile.block.cache.datablocks
> Default would be true.
> Setting this to false allows HBase in a mode where only index blocks are
> cached, which is useful for analytical scenarios where a useful working set
> of the data cannot be expected to fit into the (aggregate) cache.
> This is the equivalent of setting cacheBlocks to false on all scans
> (including scans on behalf of gets).
> I would like to get a general feeling about what folks think about this.
> The change itself would be simple.
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