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https://issues.apache.org/jira/browse/HBASE-8001?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13596868#comment-13596868
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Lars Hofhansl commented on HBASE-8001:
--------------------------------------
In my scenario I can not measure an improvement:
* all data in the blockcache
* 40m small KVs (8 byte keys, 20 byte values) across two CFs
* scan + filter where filter filters everything at the server
* column family with a single column
* VERSIONS=1
* table is fully compacted
Tests:
* adding a single family to Scan object: 11.8
* adding the family+column to the Scan object: 13.1
I get the same numbers with or without the patch. The 2nd number should have
improved.
> Avoid unnecessary lazy seek
> ---------------------------
>
> Key: HBASE-8001
> URL: https://issues.apache.org/jira/browse/HBASE-8001
> Project: HBase
> Issue Type: Improvement
> Components: regionserver
> Affects Versions: 0.94.5
> Reporter: Raymond Liu
> Assignee: Raymond Liu
> Fix For: 0.98.0
>
> Attachments: HBASE-8001_onescanner.patch
>
>
> Lazy seek helps to reduce the real seek needed for multi hfile, when the kv
> from newer hfile is enough to satisfy the query.
> While in many case, it just push the real seek later, and do not reduce the
> number of real seek. e.g. there are only one hfile, or storefilescanner is
> closed and only one left, or the scan need to go through all the versions, or
> there are only one version of row and a sequence scan is performed. In these
> case, lazy seek just bring extra overhead.
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