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From "Jeremy (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CASSANDRA-16) Memory efficient compactions
Date Thu, 08 Apr 2010 16:53:36 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-16?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12855002#action_12855002
] 

Jeremy commented on CASSANDRA-16:
---------------------------------


When this is finally resolved do you see this as being a fix that mostly protects from OOM
cases, but really, a user shouldn't intentionally design a scenario that might create very
large (ever growing) CF because of performance penalties... OR Is this is a fix that (as long
as you have sufficient disk and modest amount of memory) handles this case just fine and a
user shouldn't worry about it anymore...



> Memory efficient compactions 
> -----------------------------
>
>                 Key: CASSANDRA-16
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-16
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>         Environment: All
>            Reporter: Sandeep Tata
>             Fix For: 0.7
>
>
> The basic idea is to allow rows to get large enough that they don't have to fit in memory
entirely, but can easily fit on a disk. The compaction algorithm today de-serializes the entire
row in memory before writing out the compacted SSTable (see ColumnFamilyStore.doCompaction()
and associated methods).
> The requirement is to have a compaction method with a lower memory requirement so we
can support rows larger than available main memory. To re-use the old FB example, if we stored
a user's inbox in a row, we'd want the inbox to grow bigger than memory so long as it fit
on disk.

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