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From "Sunitha Kambhampati (JIRA)" <derby-...@db.apache.org>
Subject [jira] Created: (DERBY-1676) Dynamically change the max merge runs in a merge phase during external sorting.
Date Fri, 11 Aug 2006 19:09:13 GMT
Dynamically change the max merge runs in a merge phase during external sorting. 
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                 Key: DERBY-1676
                 URL: http://issues.apache.org/jira/browse/DERBY-1676
             Project: Derby
          Issue Type: Improvement
          Components: Store
    Affects Versions: 10.1.3.1, 10.1.3.0, 10.1.2.1, 10.1.1.0, 10.0.2.1, 10.0.2.0, 10.2.0.0
            Reporter: Sunitha Kambhampati


Please see solution #3 proposed in DERBY-1660 notes. 
http://issues.apache.org/jira/secure/attachment/12338618/1661_Notes.txt

Currently, the max number of open files for a merge phase is 512.  Worst case, the sort module
can keep 512 open files per connection during the merge phase.  It seems that we should be
able to dynamically change the max merge runs. 

Even though the 512 limit is there, it is very much possible to hit the too many file descriptor
limit given other files open on the system. One interesting solution would be to catch the
FileNotFoundException that gets thrown when during the scan , when an error happens on  opening
the merge run file and dynamically change the max_merge_runs to accommadate this.  

This jira is to investigate this issue.

More improvements are possible in the sort module, see derby-1660.


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