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From "Paulo Motta (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (CASSANDRA-9830) Option to disable bloom filter in highest level of LCS sstables
Date Wed, 18 Nov 2015 17:44:10 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-9830?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15011504#comment-15011504
] 

Paulo Motta edited comment on CASSANDRA-9830 at 11/18/15 5:43 PM:
------------------------------------------------------------------

Rebased to latest trunk and squashed.

* [branch|https://github.com/apache/cassandra/compare/trunk...pauloricardomg:9830-trunk-rebased]
* [testall|http://cassci.datastax.com/view/Dev/view/paulomotta/job/pauloricardomg-9830-trunk-rebased-testall/lastCompletedBuild/testReport/]
* [dtest|http://cassci.datastax.com/view/Dev/view/paulomotta/job/pauloricardomg-9830-trunk-rebased-dtest/lastCompletedBuild/testReport/]


was (Author: pauloricardomg):
Rebased to latest trunk and squased.

* [branch|https://github.com/apache/cassandra/compare/trunk...pauloricardomg:9830-trunk-rebased]
* [testall|http://cassci.datastax.com/view/Dev/view/paulomotta/job/pauloricardomg-9830-trunk-rebased-testall/lastCompletedBuild/testReport/]
* [dtest|http://cassci.datastax.com/view/Dev/view/paulomotta/job/pauloricardomg-9830-trunk-rebased-dtest/lastCompletedBuild/testReport/]

> Option to disable bloom filter in highest level of LCS sstables
> ---------------------------------------------------------------
>
>                 Key: CASSANDRA-9830
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9830
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Compaction
>            Reporter: Jonathan Ellis
>            Assignee: Paulo Motta
>            Priority: Minor
>              Labels: performance
>             Fix For: 3.x
>
>
> We expect about 90% of data to be in the highest level of LCS in a fully populated series.
 (See also CASSANDRA-9829.)
> Thus if the user is primarily asking for data (partitions) that has actually been inserted,
the bloom filter on the highest level only helps reject sstables about 10% of the time.
> We should add an option that suppresses bloom filter creation on top-level sstables.
 This will dramatically reduce memory usage for LCS and may even improve performance as we
no longer check a low-value filter.
> (This is also an idea from RocksDB.)



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