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From "Jonathan Ellis (Created) (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-3952) avoid quadratic startup time in LeveledManifest
Date Thu, 23 Feb 2012 18:14:48 GMT
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
            Assignee: Jonathan Ellis
            Priority: Minor
             Fix For: 1.1.0, 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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