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https://issues.apache.org/jira/browse/CASSANDRA-9486?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14564801#comment-14564801
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Marcus Eriksson commented on CASSANDRA-9486:
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Unless I misunderstand your description, we do update(...) the normal cells as
well, in ColumnIndex.Builder.add(...);
But, I guess, if you have a very wide partition with "only" range tombstones,
you can hit this, will add some remove logic when adding a RT as well
> LazilyCompactedRow accumulates all expired RangeTombstones
> ----------------------------------------------------------
>
> Key: CASSANDRA-9486
> URL: https://issues.apache.org/jira/browse/CASSANDRA-9486
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Reporter: Benedict
> Assignee: Marcus Eriksson
> Fix For: 3.x, 2.1.x, 2.0.x, 2.2.x, 1.2.x
>
> Attachments: 0001-9486.patch
>
>
> LazilyCompactedRow initializes a ColumnIndex.Builder to use its
> RangeTombstone.Tracker, but it only calls update() with a RT argument, never
> an atom. The Tracker only ever _adds_ if it receives a RT, never removes. So
> all the RT ever seen for the partition (that have expired) remain in memory
> until the compaction completes. To make matters worse, this then forces a
> linear scan of all of these RT for each live cell we add, so this extra load
> hangs around for a long time, and compactions stall.
> This issue is biting one of our users badly (at least, it seems likely to be
> this issue), and there may be others. This user is not even making use of RT
> extensively themselves, only collections (presumably with a complete
> overwrite of the contents of the collection, resulting in a RT being
> generated).
> Probably the best solution is to make the RT addition itself remove any
> already present that are no longer helpful.
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