THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
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- select the source file
- log the source file list one by one
- log `sequence` flag
- create the target file
- log the target file
- start merge process
- if finish merge a device, log (`device` `writer.offset`)
- generate *.resource file
- writer.endFile
- log `merge finished`
- delete source files
- delete the ${storagegroup}.compaction.log file
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