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https://issues.apache.org/jira/browse/CASSANDRA-8547?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14567278#comment-14567278
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Sylvain Lebresne commented on CASSANDRA-8547:
---------------------------------------------
Maybe Tyler meant CASSANDRA-9486?
And I do think the actual problem is the one pointed in CASSANDRA-9486. The
idea behind {{RangeTombstone.Tracker}} is that it only tracks tombstones that
are actually useful, i.e. those that still cover something. As such, the linear
scan of {{isDeleted}} shouldn't be a problem, it shouldn't scan anything
uselessly. However, and that's what CASSANDRA-9486, the tracker is not always
use properly, and there is cases where it's {{update}} method is not called,
resulting in the non-expected higher cost in {{isDeleted}}. In practice, I'm
sure the attached patch does improve things, but that's not really the right
fix. And as the right fix is being discussed on CASSANDRA-9486 already, I'm
going to mark this as a duplicate.
> Make RangeTombstone.Tracker.isDeleted() faster
> ----------------------------------------------
>
> Key: CASSANDRA-8547
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8547
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Environment: 2.0.11
> Reporter: Dominic Letz
> Assignee: Dominic Letz
> Labels: tombstone
> Fix For: 2.1.x
>
> Attachments: Selection_044.png, cassandra-2.0.11-8547.txt,
> cassandra-2.1-8547.txt, rangetombstone.tracker.txt
>
>
> During compaction and repairs with many tombstones an exorbitant amount of
> time is spend in RangeTombstone.Tracker.isDeleted().
> The amount of time spend there can be so big that compactions and repairs
> look "stalled" and the time remaining time estimated frozen at the same value
> for days.
> Using visualvm I've been sample profiling the code during execution and both
> in Compaction as well as during repairs found this. (point in time backtraces
> attached)
> Looking at the code the problem is obviously the linear scanning:
> {code}
> public boolean isDeleted(Column column)
> {
> for (RangeTombstone tombstone : ranges)
> {
> if (comparator.compare(column.name(), tombstone.min) >= 0
> && comparator.compare(column.name(), tombstone.max) <= 0
> && tombstone.maxTimestamp() >= column.timestamp())
> {
> return true;
> }
> }
> return false;
> }
> {code}
> I would like to propose to change this and instead use a sorted list (e.g.
> RangeTombstoneList) here instead.
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