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From "Jonathan Ellis (JIRA)" <>
Subject [jira] Commented: (CASSANDRA-436) OOM during major compaction on many (hundreds) of sstables
Date Mon, 14 Sep 2009 17:50:57 GMT


Jonathan Ellis commented on CASSANDRA-436:

    Replace PriorityQueue mess with a CompactionIterator that efficiently yields compacted
Rows from a set of
    sstables by feeding CollationIterator into a ReducingIterator transform.  ("Efficiently"
means we        
    never deserialize data until it is needed, so the number of sstables that can be compacted
at once is    
    virtually unlimited, and if only one sstable contains a given key that row data will be
copied over      
    without an intermediate de/serialize step.) This is a very natural fit               
    for the compaction algorithm and almost entirely gets rid of duplicated code between doFileCompaction

    allow ReducingIterator to reduce from one type to a different one

    copy FileStruct to SSTableScanner and remove cruft.  Migrate getKeyRange to new scanner

    minor cleanup

> OOM during major compaction on many (hundreds) of sstables
> ----------------------------------------------------------
>                 Key: CASSANDRA-436
>                 URL:
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Jonathan Ellis
>            Assignee: Jonathan Ellis
>             Fix For: 0.5
>         Attachments: 0001-CASSANDRA-436-minor-fixes.txt, 0002-copy-FileStruct-to-SSTableScanner-and-remove-cruft.-M.txt,
0003-allow-ReducingIterator-to-reduce-from-one-type-to-a-di.txt, 0004-Replace-PriorityQueue-mess-with-a-CompactionIterator-t.txt
> compaction deserializes rows during compaction before they are needed, one per sstable.
 if we only deserialized on-demand the current algorithm would be fine on nearly arbitrarily
large numbers of sstables.  (this is only important b/c it is useful to disable compactions
during bulk load.)

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