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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CASSANDRA-16) Memory efficient compactions
Date Fri, 31 Jul 2009 16:12:14 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-16?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12737582#action_12737582
] 

Jonathan Ellis commented on CASSANDRA-16:
-----------------------------------------

sure, if you want to add two seeks per row (first back to the hole, second to reposition for
the next row).

I'd rather maintain our No Seeking For Writes design than have huge rows.

> 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
>            Priority: Critical
>             Fix For: 0.5
>
>
> 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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