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https://issues.apache.org/jira/browse/HBASE-24742?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17157791#comment-17157791
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Andrew Kyle Purtell edited comment on HBASE-24742 at 7/15/20, 1:35 AM:
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There is a regression in SKIP hint handling in branch-2, see HBASE-24637. Is
this related?
In the HBASE-24637 case the difference is not so much more comparisons on a hot
path, which would be good to fix of course, no question, but a regression with
wider scope with respect to reseeking (I/O) that causes, proportional to number
of cells/columns, more work in the whole stack from file or blockcache to hfile
reader up to SQM.
I went out on vacation (and am still out) before tracking this down. I was/am
planning a review of any commit that touches SQM and friends. This was a bit
daunting because (I am guessing) the number of commits from circa 1.3 to 2.2 is
more than a handful. Maybe not, that would be nice. Perhaps this issue finds it
but I suspect more changes in this area were committed after HBASE-17958 and
HBASE-19863.
was (Author: apurtell):
There is a regression in SKIP hint handling in branch-2, see HBASE-24637. Is
this related?
In the HBASE-24637 case the difference is not so much more comparisons on a hot
path, which would be good to fix, but a regression with wider scope with
respect to reseeking (I/O) that causes, proportional to number of
cells/columns, more work in the whole stack from file or blockcache to hfile
reader up to SQM.
I went out on vacation (and am still out) before tracking this down. I was/am
planning a review of any commit that touches SQM and friends. This was a bit
daunting because (I am guessing) the number of commits from circa 1.3 to 2.2 is
more than a handful. Maybe not, that would be nice. Perhaps this issue finds it
but I suspect more changes in this area were committed after HBASE-17958 and
HBASE-19863.
> Improve performance of SKIP vs SEEK logic
> -----------------------------------------
>
> Key: HBASE-24742
> URL: https://issues.apache.org/jira/browse/HBASE-24742
> Project: HBase
> Issue Type: Bug
> Components: Performance, regionserver
> Affects Versions: 3.0.0-alpha-1, 1.7.0, 2.4.0
> Reporter: Lars Hofhansl
> Assignee: Lars Hofhansl
> Priority: Major
> Attachments: hbase-24742-branch-1.txt
>
>
> In our testing of HBase 1.3 against the current tip of branch-1 we saw a 30%
> slowdown in scanning scenarios.
> We tracked it back to HBASE-17958 and HBASE-19863.
> Both add comparisons to one of the tightest HBase has.
> [~bharathv]
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