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From "Keith Turner (JIRA)" <>
Subject [jira] [Created] (ACCUMULO-550) Colocate rfile index entries within file
Date Fri, 20 Apr 2012 22:27:33 GMT
Keith Turner created ACCUMULO-550:

             Summary: Colocate rfile index entries within file
                 Key: ACCUMULO-550
             Project: Accumulo
          Issue Type: Improvement
          Components: tserver
            Reporter: Keith Turner
            Assignee: Keith Turner
             Fix For: 1.5.0

Before multi-level indexes were introduced, when an an rfile was written its entire index
was held in memory and written out then the file was closed.  With the introduction of multilevel
index each index block is written when it fills up as the file is being written.  This was
done to handle the case where the index may not fit into memory.  This leads to index blocks
being sprinkled through the file.   So any operation that iterates over the entire index can
be slow because it turns into a lot of random accesses.   

One possible solution is to buffer lots of index blocks up to some some threshold and write
out alot of index blocks at once.  This would make a scan of the index much faster as it would
turn into a set of sequential reads of large chunks of data.

Could buffer all block at a particular level and write them out when the parent index block
fills up.

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