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From "Dave Brosius (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-3952) avoid quadratic startup time in LeveledManifest
Date Sat, 03 Mar 2012 05:08:02 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-3952?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13221518#comment-13221518
] 

Dave Brosius commented on CASSANDRA-3952:
-----------------------------------------

Could the SSTableReader just have a field that held what level it was, and is set when LeveledManifest.add
and .remove were called?
                
> avoid quadratic startup time in LeveledManifest
> -----------------------------------------------
>
>                 Key: CASSANDRA-3952
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3952
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Jonathan Ellis
>            Priority: Minor
>              Labels: lhf
>             Fix For: 1.1.1
>
>
> Checking that each sstable is in the manifest on startup is O(N**2) in the number of
sstables:
> {code}
> .       // ensure all SSTables are in the manifest
>         for (SSTableReader ssTableReader : cfs.getSSTables())
>         {
>             if (manifest.levelOf(ssTableReader) < 0)
>                 manifest.add(ssTableReader);
>         }
> {code}
> {code}
> private int levelOf(SSTableReader sstable)
> {
>     for (int level = 0; level < generations.length; level++)
>     {
>         if (generations[level].contains(sstable))
>             return level;
>     }
>     return -1;
> }
> {code}
> Note that the contains call is a linear List.contains.
> We need to switch to a sorted list and bsearch, or a tree, to support TB-levels of data
in LeveledCompactionStrategy.

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