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From "Mck SembWever (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 Wed, 02 Nov 2011 21:39:33 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-3427?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13142576#comment-13142576
] 

Mck SembWever commented on CASSANDRA-3427:
------------------------------------------

Or use a ConcurrentLinkedHashMap w/ fixed capacity?
                
> 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: 3427.patch
>
>
> 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.

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