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From "Sylvain Lebresne (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-9486) LazilyCompactedRow accumulates all expired RangeTombstones
Date Tue, 02 Jun 2015 09:00:46 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-9486?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14568806#comment-14568806
] 

Sylvain Lebresne commented on CASSANDRA-9486:
---------------------------------------------

bq. we switched maxOrderingSet to a LinkedList

Make sense, I've pushed the update. I'll wait for the CI to run on it and commit, unless you
have remarks on that last versions.

> 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: Sylvain Lebresne
>            Priority: Critical
>             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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