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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