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https://issues.apache.org/jira/browse/HBASE-17958?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16208801#comment-16208801
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Lars Hofhansl edited comment on HBASE-17958 at 10/18/17 4:40 AM:
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So I just ran a things through a profiler for some unrelated stuff and now find
that a whopping *third* of the time for the scan I am doing is spent in
{{trySkipToNextRow}}. That is certainly what I had intended with my original
idea.
Looking into that function (in branch-1) I see that each time we SKIP
(heap.next()) we re-check the next indexed key.
It's entirely possible that I am missing something... But it seems to me we
should check for SEEK outside of the loop once, then either return false, or
unconditionally continue SKIP'ing along.
[~Apache9], [~zghaobac].
was (Author: lhofhansl):
So I just ran a things through a profiler for some unrelated stuff and now find
that a whopping *third* of the scan I am doing is spent in
{{trySkipToNextRow}}. That is certainly what I had intended with my original
idea.
Looking into that function (in branch-1) I see that each time we SKIP
(heap.next()) we re-check the next indexed key.
It's entirely possible that I am missing something... But it seems to me we
should check for SEEK outside of the loop once, then either return false, or
unconditionally continue SKIP'ing along.
[~Apache9], [~zghaobac].
> Avoid passing unexpected cell to ScanQueryMatcher when optimize SEEK to SKIP
> ----------------------------------------------------------------------------
>
> Key: HBASE-17958
> URL: https://issues.apache.org/jira/browse/HBASE-17958
> Project: HBase
> Issue Type: Bug
> Reporter: Guanghao Zhang
> Assignee: Guanghao Zhang
> Fix For: 2.0.0, 1.4.0
>
> Attachments: 0001-add-one-ut-testWithColumnCountGetFilter.patch,
> HBASE-17958-branch-1.patch, HBASE-17958-branch-1.patch,
> HBASE-17958-branch-1.patch, HBASE-17958-branch-1.patch, HBASE-17958-v1.patch,
> HBASE-17958-v2.patch, HBASE-17958-v3.patch, HBASE-17958-v4.patch,
> HBASE-17958-v5.patch, HBASE-17958-v6.patch, HBASE-17958-v7.patch,
> HBASE-17958-v7.patch
>
>
> {code}
> ScanQueryMatcher.MatchCode qcode = matcher.match(cell);
> qcode = optimize(qcode, cell);
> {code}
> The optimize method may change the MatchCode from SEEK_NEXT_COL/SEEK_NEXT_ROW
> to SKIP. But it still pass the next cell to ScanQueryMatcher. It will get
> wrong result when use some filter, etc. ColumnCountGetFilter. It just count
> the columns's number. If pass a same column to this filter, the count result
> will be wrong. So we should avoid passing cell to ScanQueryMatcher when
> optimize SEEK to SKIP.
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