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From "Sylvain Lebresne (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-3427) CompressionMetadata is not shared across threads, we create a new one for each read
Date Mon, 14 Nov 2011 21:02:51 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-3427?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13149911#comment-13149911
] 

Sylvain Lebresne commented on CASSANDRA-3427:
---------------------------------------------

That's the stupidest bug ever. It happens we interpret the chunk_length_in_kb not in kb but
in bytes.
Anyway, I've created CASSANDRA-3492 to address this.
Turns out if you don't update the chunk_length you're fine because the default is ok, but
I guess hitting this issue initially has put you in the wrong spot :(
                
> CompressionMetadata is not shared across threads, we create a new one for each read
> -----------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-3427
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3427
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 1.0.0
>            Reporter: Sylvain Lebresne
>            Assignee: Sylvain Lebresne
>              Labels: compression
>             Fix For: 1.0.2
>
>         Attachments: 0001-debugging.patch, 3427.patch, 3427_v2.patch, CASSANDRA-3427.patch,
jmx_jvm_memory-month.png, jmx_jvm_memory-week.png
>
>
> The CompressionMetada holds the compressed block offsets in memory. Without being absolutely
huge, this is still of non-negligible size as soon as you have a bit of data in the DB. Reallocating
this for each read is a very bad idea.
> Note that this only affect range queries, since "normal" queries uses CompressedSegmentedFile
that does reuse a unique CompressionMetadata instance.
> ( Background: http://thread.gmane.org/gmane.comp.db.cassandra.user/21362 )

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