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Date: Fri, 11 Jun 2010 17:15:23 -0400 (EDT)
From: "Jonathan Ellis (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
Subject: [jira] Commented: (CASSANDRA-16) Memory efficient compactions
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    [ https://issues.apache.org/jira/browse/CASSANDRA-16?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12877968#action_12877968 ] 

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

rebased.

note that besides LazilyCompactedRowTest (which checks that in-memory and on-disk compactions produce the same result), you can change

        if (rowSize > DatabaseDescriptor.getInMemoryCompactionLimit())

to 

        if (true)

to force the rest of the test suite to use LCR (on-disk compaction).

> 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
>            Assignee: Jonathan Ellis
>             Fix For: 0.7
>
>         Attachments: 0001-introduce-AbstractCompactedRow-PrecompactedRow.txt, 0002-make-single-pass-over-columns-for-indexing.txt, 0003-r-m-object-count-abomination.-fix-BF-serialization-to-.txt, 0004-add-LazilyCompactedRow.txt, 0005-make-row-size-64-bits.txt, 0006-make-row-size-at-which-to-drop-to-incremental-compacti.txt
>
>
> 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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