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From "Dominic Letz (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-8546) RangeTombstoneList becoming bottleneck on tombstone heavy tasks
Date Mon, 05 Jan 2015 05:05:35 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-8546?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Dominic Letz updated CASSANDRA-8546:
------------------------------------
    Attachment: cassandra-2.1-8546.txt
                cassandra-2.0.11-8546.txt

Seems I'm the only one having fun with this one. I've done some more profiling and found that
when there are is a pendulum between middle-inserts and searching the GapLists own binarySearch
is not performing well as it "normalizes" the GapList on each search. 
In this update I'm using the built-in Collections.binarySearch instead.

> RangeTombstoneList becoming bottleneck on tombstone heavy tasks
> ---------------------------------------------------------------
>
>                 Key: CASSANDRA-8546
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8546
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>         Environment: 2.0.11 / 2.1
>            Reporter: Dominic Letz
>            Assignee: Dominic Letz
>             Fix For: 2.1.3
>
>         Attachments: cassandra-2.0.11-8546.txt, cassandra-2.1-8546.txt, tombstone_test.tgz
>
>
> I would like to propose a change of the data structure used in the RangeTombstoneList
to store and insert tombstone ranges to something with at least O(log N) insert in the middle
and at near O(1) and start AND end. Here is why:
> When having tombstone heavy work-loads the current implementation of RangeTombstoneList
becomes a bottleneck with slice queries.
> Scanning the number of tombstones up to the default maximum (100k) can take up to 3 minutes
of how addInternal() scales on insertion of middle and start elements.
> The attached test shows that with 50k deletes from both sides of a range.
> INSERT 1...110000
> flush()
> DELETE 1...50000
> DELETE 110000...60000
> While one direction performs ok (~400ms on my notebook):
> {code}
> SELECT * FROM timeseries WHERE name = 'a' ORDER BY timestamp DESC LIMIT 1
> {code}
> The other direction underperforms (~7seconds on my notebook)
> {code}
> SELECT * FROM timeseries WHERE name = 'a' ORDER BY timestamp ASC LIMIT 1
> {code}



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